Skip to content
This repository
branch: master
Fetching contributors…

Cannot retrieve contributors at this time

file 1349 lines (1165 sloc) 48.378 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349
-----------------------------------------------------------------------------
-- |
-- Module : Text.PrettyPrint.ANSI.Leijen
-- Copyright : Daan Leijen (c) 2000, http://www.cs.uu.nl/~daan
-- Max Bolingbroke (c) 2008, http://blog.omega-prime.co.uk
-- License : BSD-style (see the file LICENSE)
--
-- Maintainer : batterseapower@hotmail.com
-- Stability : provisional
-- Portability : portable
--
-- Pretty print module based on Philip Wadler's \"prettier printer\"
--
-- @
-- \"A prettier printer\"
-- Draft paper, April 1997, revised March 1998.
-- <http://cm.bell-labs.com/cm/cs/who/wadler/papers/prettier/prettier.ps>
-- @
--
-- PPrint is an implementation of the pretty printing combinators
-- described by Philip Wadler (1997). In their bare essence, the
-- combinators of Wadler are not expressive enough to describe some
-- commonly occurring layouts. The PPrint library adds new primitives
-- to describe these layouts and works well in practice.
--
-- The library is based on a single way to concatenate documents,
-- which is associative and has both a left and right unit. This
-- simple design leads to an efficient and short implementation. The
-- simplicity is reflected in the predictable behaviour of the
-- combinators which make them easy to use in practice.
--
-- A thorough description of the primitive combinators and their
-- implementation can be found in Philip Wadler's paper
-- (1997). Additions and the main differences with his original paper
-- are:
--
-- * The nil document is called empty.
--
-- * The above combinator is called '<$>'. The operator '</>' is used
-- for soft line breaks.
--
-- * There are three new primitives: 'align', 'fill' and
-- 'fillBreak'. These are very useful in practice.
--
-- * Lots of other useful combinators, like 'fillSep' and 'list'.
--
-- * There are two renderers, 'renderPretty' for pretty printing and
-- 'renderCompact' for compact output. The pretty printing algorithm
-- also uses a ribbon-width now for even prettier output.
--
-- * There are two displayers, 'displayS' for strings and 'displayIO' for
-- file based output.
--
-- * There is a 'Pretty' class.
--
-- * The implementation uses optimised representations and strictness
-- annotations.
--
-- Full documentation for the original wl-pprint library available at
-- <http://www.cs.uu.nl/~daan/download/pprint/pprint.html>.
--
-- The library has been extended to allow formatting text for output
-- to ANSI style consoles. New combinators allow:
--
-- * Control of foreground and background color of text
--
-- * The abliity to make parts of the text bold or underlined
--
-- This functionality is, as far as possible, portable across platforms
-- with their varying terminals. However, one thing to be particularly
-- wary of is that console colors will not be displayed on Windows unless
-- the 'Doc' value is output using the 'putDoc' function or one of it's
-- friends. Rendering the 'Doc' to a 'String' and then outputing /that/
-- will only work on Unix-style operating systems.
-----------------------------------------------------------
module Text.PrettyPrint.ANSI.Leijen (
   -- * Documents
   Doc, putDoc, hPutDoc,

   -- * Basic combinators
   empty, char, text, (<>), nest, line, linebreak, group, softline,
   softbreak, hardline, flatAlt, renderSmart,

   -- * Alignment
   --
   -- The combinators in this section can not be described by Wadler's
   -- original combinators. They align their output relative to the
   -- current output position - in contrast to @nest@ which always
   -- aligns to the current nesting level. This deprives these
   -- combinators from being \`optimal\'. In practice however they
   -- prove to be very useful. The combinators in this section should
   -- be used with care, since they are more expensive than the other
   -- combinators. For example, @align@ shouldn't be used to pretty
   -- print all top-level declarations of a language, but using @hang@
   -- for let expressions is fine.
   align, hang, indent, encloseSep, list, tupled, semiBraces,

   -- * Operators
   (<+>), (<$>), (</>), (<$$>), (<//>),

   -- * List combinators
   hsep, vsep, fillSep, sep, hcat, vcat, fillCat, cat, punctuate,

   -- * Fillers
   fill, fillBreak,

   -- * Bracketing combinators
   enclose, squotes, dquotes, parens, angles, braces, brackets,

   -- * Character documents
   lparen, rparen, langle, rangle, lbrace, rbrace, lbracket, rbracket,
   squote, dquote, semi, colon, comma, space, dot, backslash, equals,
   
   -- * Colorisation combinators
   black, red, green, yellow, blue, magenta, cyan, white,
   dullblack, dullred, dullgreen, dullyellow, dullblue, dullmagenta, dullcyan, dullwhite,
   onblack, onred, ongreen, onyellow, onblue, onmagenta, oncyan, onwhite,
   ondullblack, ondullred, ondullgreen, ondullyellow, ondullblue, ondullmagenta, ondullcyan, ondullwhite,

   -- * Emboldening combinators
   bold, debold,
   
   -- * Underlining combinators
   underline, deunderline,

   -- * Removing formatting
   plain,

   -- * Primitive type documents
   string, int, integer, float, double, rational,

   -- * Pretty class
   Pretty(..),

   -- * Rendering
   SimpleDoc(..), renderPretty, renderCompact, displayS, displayIO

   -- * Undocumented
        , bool

        , column, columns, nesting, width

        ) where

import System.IO (Handle,hPutStr,hPutChar,stdout)

import System.Console.ANSI (Color(..), ColorIntensity(..), ConsoleLayer(..),
                            Underlining(..), ConsoleIntensity(..),
                            SGR(..), hSetSGR, setSGRCode)

import Data.String (IsString(..))
import Data.Maybe (catMaybes)
import Data.Monoid (Monoid, mappend, mconcat, mempty)


infixr 5 </>,<//>,<$>,<$$>
infixr 6 <>,<+>


-----------------------------------------------------------
-- list, tupled and semiBraces pretty print a list of
-- documents either horizontally or vertically aligned.
-----------------------------------------------------------


-- | The document @(list xs)@ comma separates the documents @xs@ and
-- encloses them in square brackets. The documents are rendered
-- horizontally if that fits the page. Otherwise they are aligned
-- vertically. All comma separators are put in front of the elements.
list :: [Doc] -> Doc
list = encloseSep lbracket rbracket comma

-- | The document @(tupled xs)@ comma separates the documents @xs@ and
-- encloses them in parenthesis. The documents are rendered
-- horizontally if that fits the page. Otherwise they are aligned
-- vertically. All comma separators are put in front of the elements.
tupled :: [Doc] -> Doc
tupled = encloseSep lparen rparen comma


-- | The document @(semiBraces xs)@ separates the documents @xs@ with
-- semi colons and encloses them in braces. The documents are rendered
-- horizontally if that fits the page. Otherwise they are aligned
-- vertically. All semi colons are put in front of the elements.
semiBraces :: [Doc] -> Doc
semiBraces = encloseSep lbrace rbrace semi

-- | The document @(encloseSep l r sep xs)@ concatenates the documents
-- @xs@ separated by @sep@ and encloses the resulting document by @l@
-- and @r@. The documents are rendered horizontally if that fits the
-- page. Otherwise they are aligned vertically. All separators are put
-- in front of the elements. For example, the combinator 'list' can be
-- defined with @encloseSep@:
--
-- > list xs = encloseSep lbracket rbracket comma xs
-- > test = text "list" <+> (list (map int [10,200,3000]))
--
-- Which is layed out with a page width of 20 as:
--
-- @
-- list [10,200,3000]
-- @
--
-- But when the page width is 15, it is layed out as:
--
-- @
-- list [10
-- ,200
-- ,3000]
-- @
encloseSep :: Doc -> Doc -> Doc -> [Doc] -> Doc
encloseSep left right sep ds
    = case ds of
        [] -> left <> right
        [d] -> left <> d <> right
        _ -> align (cat (zipWith (<>) (left : repeat sep) ds) <> right)


-----------------------------------------------------------
-- punctuate p [d1,d2,...,dn] => [d1 <> p,d2 <> p, ... ,dn]
-----------------------------------------------------------


-- | @(punctuate p xs)@ concatenates all documents in @xs@ with
-- document @p@ except for the last document.
--
-- > someText = map text ["words","in","a","tuple"]
-- > test = parens (align (cat (punctuate comma someText)))
--
-- This is layed out on a page width of 20 as:
--
-- @
-- (words,in,a,tuple)
-- @
--
-- But when the page width is 15, it is layed out as:
--
-- @
-- (words,
-- in,
-- a,
-- tuple)
-- @
--
-- (If you want put the commas in front of their elements instead of
-- at the end, you should use 'tupled' or, in general, 'encloseSep'.)
punctuate :: Doc -> [Doc] -> [Doc]
punctuate p [] = []
punctuate p [d] = [d]
punctuate p (d:ds) = (d <> p) : punctuate p ds


-----------------------------------------------------------
-- high-level combinators
-----------------------------------------------------------


-- | The document @(sep xs)@ concatenates all documents @xs@ either
-- horizontally with @(\<+\>)@, if it fits the page, or vertically with
-- @(\<$\>)@.
--
-- > sep xs = group (vsep xs)
sep :: [Doc] -> Doc
sep = group . vsep

-- | The document @(fillSep xs)@ concatenates documents @xs@
-- horizontally with @(\<+\>)@ as long as its fits the page, than
-- inserts a @line@ and continues doing that for all documents in
-- @xs@.
--
-- > fillSep xs = foldr (\<\/\>) empty xs
fillSep :: [Doc] -> Doc
fillSep = fold (</>)

-- | The document @(hsep xs)@ concatenates all documents @xs@
-- horizontally with @(\<+\>)@.
hsep :: [Doc] -> Doc
hsep = fold (<+>)


-- | The document @(vsep xs)@ concatenates all documents @xs@
-- vertically with @(\<$\>)@. If a 'group' undoes the line breaks
-- inserted by @vsep@, all documents are separated with a space.
--
-- > someText = map text (words ("text to lay out"))
-- >
-- > test = text "some" <+> vsep someText
--
-- This is layed out as:
--
-- @
-- some text
-- to
-- lay
-- out
-- @
--
-- The 'align' combinator can be used to align the documents under
-- their first element
--
-- > test = text "some" <+> align (vsep someText)
--
-- Which is printed as:
--
-- @
-- some text
-- to
-- lay
-- out
-- @
vsep :: [Doc] -> Doc
vsep = fold (<$>)

-- | The document @(cat xs)@ concatenates all documents @xs@ either
-- horizontally with @(\<\>)@, if it fits the page, or vertically with
-- @(\<$$\>)@.
--
-- > cat xs = group (vcat xs)
cat :: [Doc] -> Doc
cat = group . vcat

-- | The document @(fillCat xs)@ concatenates documents @xs@
-- horizontally with @(\<\>)@ as long as its fits the page, than inserts
-- a @linebreak@ and continues doing that for all documents in @xs@.
--
-- > fillCat xs = foldr (\<\/\/\>) empty xs
fillCat :: [Doc] -> Doc
fillCat = fold (<//>)

-- | The document @(hcat xs)@ concatenates all documents @xs@
-- horizontally with @(\<\>)@.
hcat :: [Doc] -> Doc
hcat = fold (<>)

-- | The document @(vcat xs)@ concatenates all documents @xs@
-- vertically with @(\<$$\>)@. If a 'group' undoes the line breaks
-- inserted by @vcat@, all documents are directly concatenated.
vcat :: [Doc] -> Doc
vcat = fold (<$$>)

fold :: (Doc -> Doc -> Doc) -> [Doc] -> Doc
fold f [] = empty
fold f ds = foldr1 f ds

-- | The document @(x \<\> y)@ concatenates document @x@ and document
-- @y@. It is an associative operation having 'empty' as a left and
-- right unit. (infixr 6)
(<>) :: Doc -> Doc -> Doc
x <> y = x `beside` y

-- | The document @(x \<+\> y)@ concatenates document @x@ and @y@ with a
-- @space@ in between. (infixr 6)
(<+>) :: Doc -> Doc -> Doc
x <+> y = x <> space <> y

-- | The document @(x \<\/\> y)@ concatenates document @x@ and @y@ with a
-- 'softline' in between. This effectively puts @x@ and @y@ either
-- next to each other (with a @space@ in between) or underneath each
-- other. (infixr 5)
(</>) :: Doc -> Doc -> Doc
x </> y = x <> softline <> y

-- | The document @(x \<\/\/\> y)@ concatenates document @x@ and @y@ with
-- a 'softbreak' in between. This effectively puts @x@ and @y@ either
-- right next to each other or underneath each other. (infixr 5)
(<//>) :: Doc -> Doc -> Doc
x <//> y = x <> softbreak <> y

-- | The document @(x \<$\> y)@ concatenates document @x@ and @y@ with a
-- 'line' in between. (infixr 5)
(<$>) :: Doc -> Doc -> Doc
x <$> y = x <> line <> y

-- | The document @(x \<$$\> y)@ concatenates document @x@ and @y@ with
-- a @linebreak@ in between. (infixr 5)
(<$$>) :: Doc -> Doc -> Doc
x <$$> y = x <> linebreak <> y

-- | The document @softline@ behaves like 'space' if the resulting
-- output fits the page, otherwise it behaves like 'line'.
--
-- > softline = group line
softline :: Doc
softline = group line

-- | The document @softbreak@ behaves like 'empty' if the resulting
-- output fits the page, otherwise it behaves like 'line'.
--
-- > softbreak = group linebreak
softbreak :: Doc
softbreak = group linebreak

-- | Document @(squotes x)@ encloses document @x@ with single quotes
-- \"'\".
squotes :: Doc -> Doc
squotes = enclose squote squote

-- | Document @(dquotes x)@ encloses document @x@ with double quotes
-- '\"'.
dquotes :: Doc -> Doc
dquotes = enclose dquote dquote

-- | Document @(braces x)@ encloses document @x@ in braces, \"{\" and
-- \"}\".
braces :: Doc -> Doc
braces = enclose lbrace rbrace

-- | Document @(parens x)@ encloses document @x@ in parenthesis, \"(\"
-- and \")\".
parens :: Doc -> Doc
parens = enclose lparen rparen

-- | Document @(angles x)@ encloses document @x@ in angles, \"\<\" and
-- \"\>\".
angles :: Doc -> Doc
angles = enclose langle rangle

-- | Document @(brackets x)@ encloses document @x@ in square brackets,
-- \"[\" and \"]\".
brackets :: Doc -> Doc
brackets = enclose lbracket rbracket

-- | The document @(enclose l r x)@ encloses document @x@ between
-- documents @l@ and @r@ using @(\<\>)@.
--
-- > enclose l r x = l <> x <> r
enclose :: Doc -> Doc -> Doc -> Doc
enclose l r x = l <> x <> r

-- | The document @lparen@ contains a left parenthesis, \"(\".
lparen :: Doc
lparen = char '('
-- | The document @rparen@ contains a right parenthesis, \")\".
rparen :: Doc
rparen = char ')'
-- | The document @langle@ contains a left angle, \"\<\".
langle :: Doc
langle = char '<'
-- | The document @rangle@ contains a right angle, \">\".
rangle :: Doc
rangle = char '>'
-- | The document @lbrace@ contains a left brace, \"{\".
lbrace :: Doc
lbrace = char '{'
-- | The document @rbrace@ contains a right brace, \"}\".
rbrace :: Doc
rbrace = char '}'
-- | The document @lbracket@ contains a left square bracket, \"[\".
lbracket :: Doc
lbracket = char '['
-- | The document @rbracket@ contains a right square bracket, \"]\".
rbracket :: Doc
rbracket = char ']'


-- | The document @squote@ contains a single quote, \"'\".
squote :: Doc
squote = char '\''
-- | The document @dquote@ contains a double quote, '\"'.
dquote :: Doc
dquote = char '"'
-- | The document @semi@ contains a semi colon, \";\".
semi :: Doc
semi = char ';'
-- | The document @colon@ contains a colon, \":\".
colon :: Doc
colon = char ':'
-- | The document @comma@ contains a comma, \",\".
comma :: Doc
comma = char ','
-- | The document @space@ contains a single space, \" \".
--
-- > x <+> y = x <> space <> y
space :: Doc
space = char ' '
-- | The document @dot@ contains a single dot, \".\".
dot :: Doc
dot = char '.'
-- | The document @backslash@ contains a back slash, \"\\\".
backslash :: Doc
backslash = char '\\'
-- | The document @equals@ contains an equal sign, \"=\".
equals :: Doc
equals = char '='


-----------------------------------------------------------
-- Combinators for prelude types
-----------------------------------------------------------

-- string is like "text" but replaces '\n' by "line"

-- | The document @(string s)@ concatenates all characters in @s@
-- using @line@ for newline characters and @char@ for all other
-- characters. It is used instead of 'text' whenever the text contains
-- newline characters.
string :: String -> Doc
string "" = empty
string ('\n':s) = line <> string s
string s = case (span (/='\n') s) of
(xs,ys) -> text xs <> string ys

bool :: Bool -> Doc
bool b = text (show b)

-- | The document @(int i)@ shows the literal integer @i@ using
-- 'text'.
int :: Int -> Doc
int i = text (show i)

-- | The document @(integer i)@ shows the literal integer @i@ using
-- 'text'.
integer :: Integer -> Doc
integer i = text (show i)

-- | The document @(float f)@ shows the literal float @f@ using
-- 'text'.
float :: Float -> Doc
float f = text (show f)

-- | The document @(double d)@ shows the literal double @d@ using
-- 'text'.
double :: Double -> Doc
double d = text (show d)

-- | The document @(rational r)@ shows the literal rational @r@ using
-- 'text'.
rational :: Rational -> Doc
rational r = text (show r)


-----------------------------------------------------------
-- overloading "pretty"
-----------------------------------------------------------

-- | The member @prettyList@ is only used to define the @instance Pretty
-- a => Pretty [a]@. In normal circumstances only the @pretty@ function
-- is used.
class Pretty a where
pretty :: a -> Doc
prettyList :: [a] -> Doc
prettyList = list . map pretty

instance Pretty a => Pretty [a] where
pretty = prettyList

instance Pretty Doc where
pretty = id

instance Pretty () where
pretty () = text "()"

instance Pretty Bool where
pretty b = bool b

instance Pretty Char where
pretty c = char c
prettyList s = string s

instance Pretty Int where
pretty i = int i

instance Pretty Integer where
pretty i = integer i

instance Pretty Float where
pretty f = float f

instance Pretty Double where
pretty d = double d


--instance Pretty Rational where
-- pretty r = rational r

instance (Pretty a,Pretty b) => Pretty (a,b) where
pretty (x,y) = tupled [pretty x, pretty y]

instance (Pretty a,Pretty b,Pretty c) => Pretty (a,b,c) where
pretty (x,y,z)= tupled [pretty x, pretty y, pretty z]

instance Pretty a => Pretty (Maybe a) where
pretty Nothing = empty
pretty (Just x) = pretty x



-----------------------------------------------------------
-- semi primitive: fill and fillBreak
-----------------------------------------------------------

-- | The document @(fillBreak i x)@ first renders document @x@. It
-- than appends @space@s until the width is equal to @i@. If the
-- width of @x@ is already larger than @i@, the nesting level is
-- increased by @i@ and a @line@ is appended. When we redefine @ptype@
-- in the previous example to use @fillBreak@, we get a useful
-- variation of the previous output:
--
-- > ptype (name,tp)
-- > = fillBreak 6 (text name) <+> text "::" <+> text tp
--
-- The output will now be:
--
-- @
-- let empty :: Doc
-- nest :: Int -> Doc -> Doc
-- linebreak
-- :: Doc
-- @
fillBreak :: Int -> Doc -> Doc
fillBreak f x = width x (\w ->
                  if (w > f) then nest f linebreak
                             else text (spaces (f - w)))


-- | The document @(fill i x)@ renders document @x@. It than appends
-- @space@s until the width is equal to @i@. If the width of @x@ is
-- already larger, nothing is appended. This combinator is quite
-- useful in practice to output a list of bindings. The following
-- example demonstrates this.
--
-- > types = [("empty","Doc")
-- > ,("nest","Int -> Doc -> Doc")
-- > ,("linebreak","Doc")]
-- >
-- > ptype (name,tp)
-- > = fill 6 (text name) <+> text "::" <+> text tp
-- >
-- > test = text "let" <+> align (vcat (map ptype types))
--
-- Which is layed out as:
--
-- @
-- let empty :: Doc
-- nest :: Int -> Doc -> Doc
-- linebreak :: Doc
-- @
fill :: Int -> Doc -> Doc
fill f d = width d (\w ->
                  if (w >= f) then empty
                              else text (spaces (f - w)))

width :: Doc -> (Int -> Doc) -> Doc
width d f = column (\k1 -> d <> column (\k2 -> f (k2 - k1)))


-----------------------------------------------------------
-- semi primitive: Alignment and indentation
-----------------------------------------------------------

-- | The document @(indent i x)@ indents document @x@ with @i@ spaces.
--
-- > test = indent 4 (fillSep (map text
-- > (words "the indent combinator indents these words !")))
--
-- Which lays out with a page width of 20 as:
--
-- @
-- the indent
-- combinator
-- indents these
-- words !
-- @
indent :: Int -> Doc -> Doc
indent i d = hang i (text (spaces i) <> d)

-- | The hang combinator implements hanging indentation. The document
-- @(hang i x)@ renders document @x@ with a nesting level set to the
-- current column plus @i@. The following example uses hanging
-- indentation for some text:
--
-- > test = hang 4 (fillSep (map text
-- > (words "the hang combinator indents these words !")))
--
-- Which lays out on a page with a width of 20 characters as:
--
-- @
-- the hang combinator
-- indents these
-- words !
-- @
--
-- The @hang@ combinator is implemented as:
--
-- > hang i x = align (nest i x)
hang :: Int -> Doc -> Doc
hang i d = align (nest i d)

-- | The document @(align x)@ renders document @x@ with the nesting
-- level set to the current column. It is used for example to
-- implement 'hang'.
--
-- As an example, we will put a document right above another one,
-- regardless of the current nesting level:
--
-- > x $$ y = align (x <$> y)
--
-- > test = text "hi" <+> (text "nice" $$ text "world")
--
-- which will be layed out as:
--
-- @
-- hi nice
-- world
-- @
align :: Doc -> Doc
align d = column (\k ->
                  nesting (\i -> nest (k - i) d)) --nesting might be negative :-)



-----------------------------------------------------------
-- Primitives
-----------------------------------------------------------

-- | The abstract data type @Doc@ represents pretty documents.
--
-- @Doc@ is an instance of the 'Show' class. @(show doc)@ pretty
-- prints document @doc@ with a page width of 100 characters and a
-- ribbon width of 40 characters.
--
-- > show (text "hello" <$> text "world")
--
-- Which would return the string \"hello\\nworld\", i.e.
--
-- @
-- hello
-- world
-- @
data Doc = Fail
                | Empty
                | Char Char -- invariant: char is not '\n'
                | Text !Int String -- invariant: text doesn't contain '\n'
                | Line
                | FlatAlt Doc Doc -- Render the first doc, but when
                                        -- flattened, render the second.
                | Cat Doc Doc
                | Nest !Int Doc
                | Union Doc Doc -- invariant: first lines of first doc longer than the first lines of the second doc
                | Column (Int -> Doc)
                | Columns (Maybe Int -> Doc)
                | Nesting (Int -> Doc)
                | Color ConsoleLayer ColorIntensity -- Introduces coloring /around/ the embedded document
                        Color Doc
                | Intensify ConsoleIntensity Doc
                | Italicize Bool Doc
                | Underline Underlining Doc
                | RestoreFormat (Maybe (ColorIntensity, Color)) -- Only used during the rendered phase, to signal a SGR should be issued to restore the terminal formatting.
                                (Maybe (ColorIntensity, Color)) -- These are the colors to revert the current forecolor/backcolor to (i.e. those from before the start of the Color block).
                                (Maybe ConsoleIntensity) -- Intensity to revert to.
                                (Maybe Bool) -- Italicization to revert to.
                                (Maybe Underlining) -- Underlining to revert to.


-- | The data type @SimpleDoc@ represents rendered documents and is
-- used by the display functions.
--
-- The @Int@ in @SText@ contains the length of the string. The @Int@
-- in @SLine@ contains the indentation for that line. The library
-- provides two default display functions 'displayS' and
-- 'displayIO'. You can provide your own display function by writing a
-- function from a @SimpleDoc@ to your own output format.
data SimpleDoc = SFail
                | SEmpty
                | SChar Char SimpleDoc
                | SText !Int String SimpleDoc
                | SLine !Int SimpleDoc
                | SSGR [SGR] SimpleDoc


-- MCB: Not in the wl-pprint package that we forked from. I added this when the "pretty" package
-- from base gained a Monoid instance (<http://hackage.haskell.org/trac/ghc/ticket/4378>):
instance Monoid Doc where
    mempty = empty
    mappend = (<>)
    mconcat = hcat

-- MCB: also added when "pretty" got the corresponding instances:
instance IsString Doc where
    fromString = text


-- | The empty document is, indeed, empty. Although @empty@ has no
-- content, it does have a \'height\' of 1 and behaves exactly like
-- @(text \"\")@ (and is therefore not a unit of @\<$\>@).
empty :: Doc
empty = Empty

-- | The document @(char c)@ contains the literal character @c@. The
-- character shouldn't be a newline (@'\n'@), the function 'line'
-- should be used for line breaks.
char :: Char -> Doc
char '\n' = line
char c = Char c

-- | The document @(text s)@ contains the literal string @s@. The
-- string shouldn't contain any newline (@'\n'@) characters. If the
-- string contains newline characters, the function 'string' should be
-- used.
text :: String -> Doc
text "" = Empty
text s = Text (length s) s

-- | The @line@ document advances to the next line and indents to the
-- current nesting level. Document @line@ behaves like @(text \" \")@
-- if the line break is undone by 'group'.
line :: Doc
line = FlatAlt Line space

-- | The @linebreak@ document advances to the next line and indents to
-- the current nesting level. Document @linebreak@ behaves like
-- 'empty' if the line break is undone by 'group'.
linebreak :: Doc
linebreak = FlatAlt Line empty

-- | A linebreak that will never be flattened; it is guaranteed to render
-- as a newline.
hardline :: Doc
hardline = Line

beside :: Doc -> Doc -> Doc
beside x y = Cat x y

-- | The document @(nest i x)@ renders document @x@ with the current
-- indentation level increased by i (See also 'hang', 'align' and
-- 'indent').
--
-- > nest 2 (text "hello" <$> text "world") <$> text "!"
--
-- outputs as:
--
-- @
-- hello
-- world
-- !
-- @
nest :: Int -> Doc -> Doc
nest i x = Nest i x

column, nesting :: (Int -> Doc) -> Doc
column f = Column f
nesting f = Nesting f

columns :: (Maybe Int -> Doc) -> Doc
columns f = Columns f

-- | The @group@ combinator is used to specify alternative
-- layouts. The document @(group x)@ undoes all line breaks in
-- document @x@. The resulting line is added to the current line if
-- that fits the page. Otherwise, the document @x@ is rendered without
-- any changes.
group :: Doc -> Doc
group x = Union (flatten x) x

-- | A document that is normally rendered as the first argument, but
-- when flattened, is rendered as the second document.
flatAlt :: Doc -> Doc -> Doc
flatAlt = FlatAlt

flatten :: Doc -> Doc
flatten (FlatAlt x y) = y
flatten (Cat x y) = Cat (flatten x) (flatten y)
flatten (Nest i x) = Nest i (flatten x)
flatten Line = Fail
flatten (Union x y) = flatten x
flatten (Column f) = Column (flatten . f)
flatten (Columns f) = Columns (flatten . f)
flatten (Nesting f) = Nesting (flatten . f)
flatten (Color l i c x) = Color l i c (flatten x)
flatten (Intensify i x) = Intensify i (flatten x)
flatten (Italicize b x) = Italicize b (flatten x)
flatten (Underline u x) = Underline u (flatten x)
flatten other = other --Empty,Char,Text,RestoreFormat


-----------------------------------------------------------
-- Colors
-----------------------------------------------------------

-- | Displays a document with the black forecolor
black :: Doc -> Doc
-- | Displays a document with the red forecolor
red :: Doc -> Doc
-- | Displays a document with the green forecolor
green :: Doc -> Doc
-- | Displays a document with the yellow forecolor
yellow :: Doc -> Doc
-- | Displays a document with the blue forecolor
blue :: Doc -> Doc
-- | Displays a document with the magenta forecolor
magenta :: Doc -> Doc
-- | Displays a document with the cyan forecolor
cyan :: Doc -> Doc
-- | Displays a document with the white forecolor
white :: Doc -> Doc
-- | Displays a document with the dull black forecolor
dullblack :: Doc -> Doc
-- | Displays a document with the dull red forecolor
dullred :: Doc -> Doc
-- | Displays a document with the dull green forecolor
dullgreen :: Doc -> Doc
-- | Displays a document with the dull yellow forecolor
dullyellow :: Doc -> Doc
-- | Displays a document with the dull blue forecolor
dullblue :: Doc -> Doc
-- | Displays a document with the dull magenta forecolor
dullmagenta :: Doc -> Doc
-- | Displays a document with the dull cyan forecolor
dullcyan :: Doc -> Doc
-- | Displays a document with the dull white forecolor
dullwhite :: Doc -> Doc
(black, dullblack) = colorFunctions Black
(red, dullred) = colorFunctions Red
(green, dullgreen) = colorFunctions Green
(yellow, dullyellow) = colorFunctions Yellow
(blue, dullblue) = colorFunctions Blue
(magenta, dullmagenta) = colorFunctions Magenta
(cyan, dullcyan) = colorFunctions Cyan
(white, dullwhite) = colorFunctions White

-- | Displays a document with a forecolor given in the first parameter
color :: Color -> Doc -> Doc
-- | Displays a document with a dull forecolor given in the first parameter
dullcolor :: Color -> Doc -> Doc
color = Color Foreground Vivid
dullcolor = Color Foreground Dull

colorFunctions :: Color -> (Doc -> Doc, Doc -> Doc)
colorFunctions what = (color what, dullcolor what)

-- | Displays a document with the black backcolor
onblack :: Doc -> Doc
-- | Displays a document with the red backcolor
onred :: Doc -> Doc
-- | Displays a document with the green backcolor
ongreen :: Doc -> Doc
-- | Displays a document with the yellow backcolor
onyellow :: Doc -> Doc
-- | Displays a document with the blue backcolor
onblue :: Doc -> Doc
-- | Displays a document with the magenta backcolor
onmagenta :: Doc -> Doc
-- | Displays a document with the cyan backcolor
oncyan :: Doc -> Doc
-- | Displays a document with the white backcolor
onwhite :: Doc -> Doc
-- | Displays a document with the dull block backcolor
ondullblack :: Doc -> Doc
-- | Displays a document with the dull red backcolor
ondullred :: Doc -> Doc
-- | Displays a document with the dull green backcolor
ondullgreen :: Doc -> Doc
-- | Displays a document with the dull yellow backcolor
ondullyellow :: Doc -> Doc
-- | Displays a document with the dull blue backcolor
ondullblue :: Doc -> Doc
-- | Displays a document with the dull magenta backcolor
ondullmagenta :: Doc -> Doc
-- | Displays a document with the dull cyan backcolor
ondullcyan :: Doc -> Doc
-- | Displays a document with the dull white backcolor
ondullwhite :: Doc -> Doc
(onblack, ondullblack) = oncolorFunctions Black
(onred, ondullred) = oncolorFunctions Red
(ongreen, ondullgreen) = oncolorFunctions Green
(onyellow, ondullyellow) = oncolorFunctions Yellow
(onblue, ondullblue) = oncolorFunctions Blue
(onmagenta, ondullmagenta) = oncolorFunctions Magenta
(oncyan, ondullcyan) = oncolorFunctions Cyan
(onwhite, ondullwhite) = oncolorFunctions White

-- | Displays a document with a backcolor given in the first parameter
oncolor :: Color -> Doc -> Doc
-- | Displays a document with a dull backcolor given in the first parameter
ondullcolor :: Color -> Doc -> Doc
oncolor = Color Background Vivid
ondullcolor = Color Background Dull

oncolorFunctions :: Color -> (Doc -> Doc, Doc -> Doc)
oncolorFunctions what = (oncolor what, ondullcolor what)


-----------------------------------------------------------
-- Console Intensity
-----------------------------------------------------------

-- | Displays a document in a heavier font weight
bold :: Doc -> Doc
bold = Intensify BoldIntensity

-- | Displays a document in the normal font weight
debold :: Doc -> Doc
debold = Intensify NormalIntensity

-- NB: I don't support FaintIntensity here because it is not widely supported by terminals.


-----------------------------------------------------------
-- Italicization
-----------------------------------------------------------

{-

I'm in two minds about providing these functions, since italicization is so rarely implemented.
It is especially bad because "italicization" may cause the meaning of colors to flip, which will
look a bit weird, to say the least...


-- | Displays a document in italics. This is not widely supported, and it's use is not recommended
italicize :: Doc -> Doc
italicize = Italicize True

-- | Displays a document with no italics
deitalicize :: Doc -> Doc
deitalicize = Italicize False

-}

-----------------------------------------------------------
-- Underlining
-----------------------------------------------------------

-- | Displays a document with underlining
underline :: Doc -> Doc
underline = Underline SingleUnderline

-- | Displays a document with no underlining
deunderline :: Doc -> Doc
deunderline = Underline NoUnderline

-- NB: I don't support DoubleUnderline here because it is not widely supported by terminals.

-----------------------------------------------------------
-- Removing formatting
-----------------------------------------------------------

-- | Removes all colorisation, emboldening and underlining from a document
plain :: Doc -> Doc
plain Fail = Fail
plain e@Empty = e
plain c@(Char _) = c
plain t@(Text _ _) = t
plain l@Line = l
plain (FlatAlt x y) = FlatAlt (plain x) (plain y)
plain (Cat x y) = Cat (plain x) (plain y)
plain (Nest i x) = Nest i (plain x)
plain (Union x y) = Union (plain x) (plain y)
plain (Column f) = Column (plain . f)
plain (Columns f) = Columns (plain . f)
plain (Nesting f) = Nesting (plain . f)
plain (Color _ _ _ x) = plain x
plain (Intensify _ x) = plain x
plain (Italicize _ x) = plain x
plain (Underline _ x) = plain x
plain (RestoreFormat _ _ _ _ _) = Empty

-----------------------------------------------------------
-- Renderers
-----------------------------------------------------------

-----------------------------------------------------------
-- renderPretty: the default pretty printing algorithm
-----------------------------------------------------------

-- list of indentation/document pairs; saves an indirection over [(Int,Doc)]
data Docs = Nil
            | Cons !Int Doc Docs


-- | This is the default pretty printer which is used by 'show',
-- 'putDoc' and 'hPutDoc'. @(renderPretty ribbonfrac width x)@ renders
-- document @x@ with a page width of @width@ and a ribbon width of
-- @(ribbonfrac * width)@ characters. The ribbon width is the maximal
-- amount of non-indentation characters on a line. The parameter
-- @ribbonfrac@ should be between @0.0@ and @1.0@. If it is lower or
-- higher, the ribbon width will be 0 or @width@ respectively.
renderPretty :: Float -> Int -> Doc -> SimpleDoc
renderPretty = renderFits fits1

-- | A slightly smarter rendering algorithm with more lookahead. It provides
-- provide earlier breaking on deeply nested structures
-- For example, consider this python-ish pseudocode:
-- @fun(fun(fun(fun(fun([abcdefg, abcdefg])))))@
-- If we put a softbreak (+ nesting 2) after each open parenthesis, and align
-- the elements of the list to match the opening brackets, this will render with
-- @renderPretty@ and a page width of 20 as:
-- @
-- fun(fun(fun(fun(fun([
-- | abcdef,
-- | abcdef,
-- ]
-- ))))) |
-- @
-- Where the 20c. boundary has been marked with |.
-- Because @renderPretty@ only uses one-line lookahead, it sees that the first
-- line fits, and is stuck putting the second and third lines after the 20-c
-- mark. In contrast, @renderSmart@ will continue to check that the potential
-- document up to the end of the indentation level. Thus, it will format the
-- document as:
--
-- @
-- fun( |
-- fun( |
-- fun( |
-- fun( |
-- fun([ |
-- abcdef,
-- abcdef,
-- ] |
-- ))))) |
-- @
-- Which fits within the 20c. boundary.
renderSmart :: Float -> Int -> Doc -> SimpleDoc
renderSmart = renderFits fitsR

renderFits :: (Int -> Int -> Int -> SimpleDoc -> Bool)
           -> Float -> Int -> Doc -> SimpleDoc
renderFits fits rfrac w x
    -- I used to do a @SSGR [Reset]@ here, but if you do that it will result
    -- in any rendered @Doc@ containing at least some ANSI control codes. This
    -- may be undesirable if you want to render to non-ANSI devices by simply
    -- not making use of the ANSI color combinators I provide.
    --
    -- What I "really" want to do here is do an initial Reset iff there is some
    -- ANSI color within the Doc, but that's a bit fiddly. I'll fix it if someone
    -- complains!
    = best 0 0 Nothing Nothing Nothing Nothing Nothing (Cons 0 x Nil)
    where
      -- r :: the ribbon width in characters
      r = max 0 (min w (round (fromIntegral w * rfrac)))

      -- best :: n = indentation of current line
      -- k = current column
      -- (ie. (k >= n) && (k - n == count of inserted characters)
      best n k mb_fc mb_bc mb_in mb_it mb_un Nil = SEmpty
      best n k mb_fc mb_bc mb_in mb_it mb_un (Cons i d ds)
        = case d of
            Fail -> SFail
            Empty -> best_typical n k ds
            Char c -> let k' = k+1 in seq k' (SChar c (best_typical n k' ds))
            Text l s -> let k' = k+l in seq k' (SText l s (best_typical n k' ds))
            Line -> SLine i (best_typical i i ds)
            FlatAlt x _ -> best_typical n k (Cons i x ds)
            Cat x y -> best_typical n k (Cons i x (Cons i y ds))
            Nest j x -> let i' = i+j in seq i' (best_typical n k (Cons i' x ds))
            Union x y -> nicest n k (best_typical n k (Cons i x ds))
                                        (best_typical n k (Cons i y ds))
            Column f -> best_typical n k (Cons i (f k) ds)
            Columns f -> best_typical n k (Cons i (f (Just w)) ds)
            Nesting f -> best_typical n k (Cons i (f i) ds)
            Color l t c x -> SSGR [SetColor l t c] (best n k mb_fc' mb_bc' mb_in mb_it mb_un (Cons i x ds_restore))
              where
                mb_fc' = case l of { Background -> mb_fc; Foreground -> Just (t, c) }
                mb_bc' = case l of { Background -> Just (t, c); Foreground -> mb_bc }
            Intensify t x -> SSGR [SetConsoleIntensity t] (best n k mb_fc mb_bc (Just t) mb_it mb_un (Cons i x ds_restore))
            Italicize t x -> SSGR [SetItalicized t] (best n k mb_fc mb_bc mb_in (Just t) mb_un (Cons i x ds_restore))
            Underline u x -> SSGR [SetUnderlining u] (best n k mb_fc mb_bc mb_in mb_it (Just u) (Cons i x ds_restore))
            RestoreFormat mb_fc' mb_bc' mb_in' mb_it' mb_un' -> SSGR sgrs (best n k mb_fc' mb_bc' mb_in' mb_it' mb_un' ds)
              where
                -- We need to be able to restore the entire SGR state, hence we carry around what we believe
                -- that state should be in all the arguments to this function. Note that in some cases we could
                -- avoid the Reset of the entire state, but not in general.
                sgrs = Reset : catMaybes [
                    fmap (uncurry (SetColor Foreground)) mb_fc',
                    fmap (uncurry (SetColor Background)) mb_bc',
                    fmap SetConsoleIntensity mb_in',
                    fmap SetItalicized mb_it',
                    fmap SetUnderlining mb_un'
                  ]
        where
          best_typical n' k' ds' = best n' k' mb_fc mb_bc mb_in mb_it mb_un ds'
          ds_restore = Cons i (RestoreFormat mb_fc mb_bc mb_in mb_it mb_un) ds

      --nicest :: r = ribbon width, w = page width,
      -- n = indentation of current line, k = current column
      -- x and y, the (simple) documents to chose from.
      -- precondition: first lines of x are longer than the first lines of y.
      nicest n k x y | fits w (min n k) width x = x
                        | otherwise = y
                        where
                          width = min (w - k) (r - k + n)

-- @fits1@ does 1 line lookahead.
fits1 :: Int -> Int -> Int -> SimpleDoc -> Bool
fits1 _ _ w x | w < 0 = False
fits1 _ _ w SFail = False
fits1 _ _ w SEmpty = True
fits1 p m w (SChar c x) = fits1 p m (w - 1) x
fits1 p m w (SText l s x) = fits1 p m (w - l) x
fits1 _ _ w (SLine i x) = True
fits1 p m w (SSGR _ x) = fits1 p m w x

-- @fitsR@ has a little more lookahead: assuming that nesting roughly
-- corresponds to syntactic depth, @fitsR@ checks that not only the current line
-- fits, but the entire syntactic structure being formatted at this level of
-- indentation fits. If we were to remove the second case for @SLine@, we would
-- check that not only the current structure fits, but also the rest of the
-- document, which would be slightly more intelligent but would have exponential
-- runtime (and is prohibitively expensive in practice).
-- p = pagewidth
-- m = minimum nesting level to fit in
-- w = the width in which to fit the first line
fitsR :: Int -> Int -> Int -> SimpleDoc -> Bool
fitsR p m w x | w < 0 = False
fitsR p m w SFail = False
fitsR p m w SEmpty = True
fitsR p m w (SChar c x) = fitsR p m (w - 1) x
fitsR p m w (SText l s x) = fitsR p m (w - l) x
fitsR p m w (SLine i x) | m < i = fitsR p m (p - i) x
                        | otherwise = True
fitsR p m w (SSGR _ x) = fitsR p m w x

-----------------------------------------------------------
-- renderCompact: renders documents without indentation
-- fast and fewer characters output, good for machines
-----------------------------------------------------------


-- | @(renderCompact x)@ renders document @x@ without adding any
-- indentation. Since no \'pretty\' printing is involved, this
-- renderer is very fast. The resulting output contains fewer
-- characters than a pretty printed version and can be used for output
-- that is read by other programs.
--
-- This rendering function does not add any colorisation information.
renderCompact :: Doc -> SimpleDoc
renderCompact x
    = scan 0 [x]
    where
      scan k [] = SEmpty
      scan k (d:ds) = case d of
                        Fail -> SFail
                        Empty -> scan k ds
                        Char c -> let k' = k+1 in seq k' (SChar c (scan k' ds))
                        Text l s -> let k' = k+l in seq k' (SText l s (scan k' ds))
                        FlatAlt x _ -> scan k (x:ds)
                        Line -> SLine 0 (scan 0 ds)
                        Cat x y -> scan k (x:y:ds)
                        Nest j x -> scan k (x:ds)
                        Union x y -> scan k (y:ds)
                        Column f -> scan k (f k:ds)
                        Columns f -> scan k (f Nothing:ds)
                        Nesting f -> scan k (f 0:ds)
                        Color _ _ _ x -> scan k (x:ds)
                        Intensify _ x -> scan k (x:ds)
                        Italicize _ x -> scan k (x:ds)
                        Underline _ x -> scan k (x:ds)
                        RestoreFormat _ _ _ _ _ -> scan k ds



-----------------------------------------------------------
-- Displayers: displayS and displayIO
-----------------------------------------------------------


-- | @(displayS simpleDoc)@ takes the output @simpleDoc@ from a
-- rendering function and transforms it to a 'ShowS' type (for use in
-- the 'Show' class).
--
-- > showWidth :: Int -> Doc -> String
-- > showWidth w x = displayS (renderPretty 0.4 w x) ""
--
-- ANSI color information will be discarded by this function unless
-- you are running on a Unix-like operating system. This is due to
-- a technical limitation in Windows ANSI support.
displayS :: SimpleDoc -> ShowS
displayS SFail = error $ "@SFail@ can not appear uncaught in a " ++
                              "rendered @SimpleDoc@"
displayS SEmpty = id
displayS (SChar c x) = showChar c . displayS x
displayS (SText l s x) = showString s . displayS x
displayS (SLine i x) = showString ('\n':indentation i) . displayS x
displayS (SSGR s x) = showString (setSGRCode s) . displayS x


-- | @(displayIO handle simpleDoc)@ writes @simpleDoc@ to the file
-- handle @handle@. This function is used for example by 'hPutDoc':
--
-- > hPutDoc handle doc = displayIO handle (renderPretty 0.4 100 doc)
--
-- Any ANSI colorisation in @simpleDoc@ will be output.
displayIO :: Handle -> SimpleDoc -> IO ()
displayIO handle simpleDoc
    = display simpleDoc
    where
      display SFail = error $ "@SFail@ can not appear uncaught in a " ++
                              "rendered @SimpleDoc@"
      display SEmpty = return ()
      display (SChar c x) = do{ hPutChar handle c; display x}
      display (SText l s x) = do{ hPutStr handle s; display x}
      display (SLine i x) = do{ hPutStr handle ('\n':indentation i); display x}
      display (SSGR s x) = do{ hSetSGR handle s; display x}

-----------------------------------------------------------
-- default pretty printers: show, putDoc and hPutDoc
-----------------------------------------------------------
instance Show Doc where
  showsPrec d doc = displayS (renderPretty 0.4 80 doc)

-- | The action @(putDoc doc)@ pretty prints document @doc@ to the
-- standard output, with a page width of 100 characters and a ribbon
-- width of 40 characters.
--
-- > main :: IO ()
-- > main = do{ putDoc (text "hello" <+> text "world") }
--
-- Which would output
--
-- @
-- hello world
-- @
--
-- Any ANSI colorisation in @doc@ will be output.
putDoc :: Doc -> IO ()
putDoc doc = hPutDoc stdout doc

-- | @(hPutDoc handle doc)@ pretty prints document @doc@ to the file
-- handle @handle@ with a page width of 100 characters and a ribbon
-- width of 40 characters.
--
-- > main = do{ handle <- openFile "MyFile" WriteMode
-- > ; hPutDoc handle (vcat (map text
-- > ["vertical","text"]))
-- > ; hClose handle
-- > }
--
-- Any ANSI colorisation in @doc@ will be output.
hPutDoc :: Handle -> Doc -> IO ()
hPutDoc handle doc = displayIO handle (renderPretty 0.4 80 doc)



-----------------------------------------------------------
-- insert spaces
-- "indentation" used to insert tabs but tabs seem to cause
-- more trouble than they solve :-)
-----------------------------------------------------------
spaces :: Int -> String
spaces n | n <= 0 = ""
                | otherwise = replicate n ' '

indentation :: Int -> String
indentation n = spaces n

--indentation n | n >= 8 = '\t' : indentation (n-8)
-- | otherwise = spaces n

-- LocalWords: PPrint combinators Wadler Wadler's encloseSep
Something went wrong with that request. Please try again.