PostScript snippets that I gone and dun.

Because who doesn't love a good gs -sDEVICE=txtwrite -sOutputFile=- -q -sBATCH -dNOPAUSE -dNOSAFER *.ps?

inspect.ps (moved to Alhadis/Inspect.ps)

A recursive inspection function that prints spiffy-looking colours to stdout. Basically, what == would be if it didn't suck at inspecting substructures:

inspect.ps was originally part of this dumb repository, but later moved to a dedicated repository. I've left this entry intact as an explanation¹ for any readers finding their way here from a link I posted to Groff's mailing list.

misc.ps

Various other shite that doesn't belong anywhere else. Even in a repository as eclectic as this one.

string bool =85 -
string =85 -

Print an Ascii85-encoded representation of a string:

(ABCD) =85 % => <~5sdq,~>

If the first operand is true, the input is treated as an /ASCIIHexEncoded bytestream, and is decoded as such first:

(ABCD)      true =85 % => <~X3C~>
(\000\200)  true =85 % => <~!.Y~>

% Whitespace is always ignored
( AB CD \n) true =85 % => <~X3C~>
< AB CD >   true =85 % => <~X3C~>

string name apply-filter string

Apply an arbitrary decoding filter to a string:

(48656C6C6F2C20776F726C642E)
/ASCIIHexDecode apply-filter % => (Hello, world.)

Currently, this doesn't work with encoding filters. See the red book for a discussion on filter types.

dict key default get? any

Retrieve the value of a dictionary entry, falling back to a default value if no such entry was found:

<< /Foo 1 >> /Foo null get? % => 1
<< /Foo 1 >> /Bar null get? % => null

any numeric? bool

Return a boolean indicating whether argument is an integer or real:

256 numeric? % => true
1.5 numeric? % => true
(1) numeric? % => false

- pagesize width height

Ascertain the physical dimensions of the device's printing area:

% When printing A4-sized pages:
pagesize % => 595.0 842.0

llx lly urx ury bboxsize width height

Resolve the dimensions of a bounding box returned from pathbbox or measuretext:

0 0 moveto
/Times-Roman findfont 10 scalefont setfont
(Hello, world.) measuretext bboxsize
% => 52.1602 8.21875

string measuretext llx lly urx ury

Compute the bounding box for the given string, expressed as the Cartesian coordinates for a rectangle's lower-left and upper-right corners.

0 0 moveto
/Times-Roman findfont 10 scalefont setfont
(Hello, world.) measuretext
% => 0.1875 -1.40625 52.3477 6.8125

array concatprocs proc

Construct a procedure by concatenating the bodies of smaller procedures. For example, to “monkey-patch” a procedure named callback, use:

Source	Output
/callback {…} def [ {[/foo /bar /baz] before} /callback load {after} ] concatprocs bind	{ [/foo /bar /baz] before … after }

geom.ps

Procedures for plotting simple geometry.

width height rect -

Draw a rectangle centred at the current point:

100 100 moveto
50 80 rect
stroke

radius circle -

Draw a circle centred at the current point:

100 100 moveto
10 circle
fill

[xRadius YRadius] sides polygon -
radius sides polygon -

Draw an 𝑁-sided polygon centred at the current point:

% Draw a 100×60-sized hexagon
100 100 moveto
[100 60] 6 polygon
stroke

% Draw a solid-filled triangle
100 100 moveto
50 3 polygon
fill

lists.ps

Despite being a stack-based language, PostScript has surprisingly limited functions for manipulating arrays and lists.² Those I deem missing will eventually find their way into this file.



Array manipulation

array last any

Retrieve the last element of an array:

[1 2 3]
last % => 1

array rev array

Return a copy of an array in reverse order:

[1 2 3]
rev % => [3 2 1]

array value append array

Append a value to an array:

[ 1 2 3 ]
4 append % => 1 2 3 4

array value prepend array

Prepend a value to an array:

[ 1 2 3 ]
4 prepend % => 4 1 2 3



Dictionary manipulation

dict keys array

Return a dictionary's keys as an array:

<< /yes true /no false >>
keys % => [/yes /no]

dict values array

Return a dictionary's values as an array:

<< /yes true /no false >>
values % => [true false]

dict entries array

Return a dictionary's concatenated key/value pairs as an array:

<< /yes true /no false >>
entries % => [/yes true /no false]

dict flip dict

Return a copy of a dictionary with its keys and values swapped:

<< /width 640 /height 480 >>
flip % => << 640 /width 480 /height >>



Operand stack manipulation

any… index nth any

Return the 𝑁^th operand if index is positive, and 𝑁^th-last if index is negative:

% Positive indices
(A)(B)(C)(D)  0 nth % => (A) (B) (C) (D) (D)
(A)(B)(C)(D)  1 nth % => (A) (B) (C) (D) (C)

% Negative indices
(A)(B)(C)(D) -1 nth % => (A) (B) (C) (D) (A)
(A)(B)(C)(D) -2 nth % => (A) (B) (C) (D) (B)

This differs from PostScript’s index operator in that indices may be negative (similar to JavaScript’s Array.prototype.slice). Note that negative offsets are indexed from 1 instead of 0 (which otherwise refers to the first/right-most operand).³

Irrespective of which end is being measured from, offsets that fall outside the operand stack will trigger a rangecheck.

any shift -

Remove the last (left-most) operand from the stack:

1 2 3 4
shift % => 2 3 4

Not to be confused with pop, which removes the first operand instead.

any unshift -

Push an operand onto the end (left-side) of the stack:

1 2 3
4 unshift % => 4 1 2 3

strings.ps

Procedures for string conversion and manipulation.

array join string
string string join string

Concatenate a list of strings:

[ (Foo) (Bar) ] join % => (FooBar)
[ (A) (B) (C) ] join % => (ABC)

If only two strings are to be concatenated, they can be passed directly as operands:

(Foo) (Bar) join % => (FooBar)

array delimiter joind string
string string delimiter joind string

Wrapper for join that inserts delimiter between each pair of strings:

[ (A) (B) (C) ]    (, ) joind % => (A, B, C)
[ (X) (Y) (Z) () ] (;)  joind % => (X;Y;Z;)
(Foo) (Bar)        (+)  joind % => (Foo+Bar)

int chr string

Return a single-character string with the given codepoint:

4 chr % => (\004)
9 chr % => (\t)

string ord int

Return the codepoint of string's first character, or 0 if the string is empty:

(ABC) ord % => 65
()    ord % => 0

Totes unserious footnotes

Footnotes

1. Also because I don't have the heart to delete that preview image's alt text. ↩
2. Yeah, okay, PostScript arrays are fixed-length records, but that still doesn't excuse the lack of operand helpers. Where's GhostScript's subr.el library, danggit? ↩
3. Confusing, I know. Signed zeroes would’ve been handy here, had PostScript implemented IEEE 754 like JavaScript did. ↩