A REPL (#138)

* A REPL based on dynamic linking and type-indexed pretty printing of natively represented values.
* Support for commands in the REPL including support for setting flags with and without arguments.
* Menu and search feature support.
* Support for loading (and compiling) mlb-files through `:load` commands.
* Automatic testing of the REPL (preliminary simple testing).
* Proper position-independent code generation on Linux (e.g., add types to global labels to avoid linker warnings).
* Set rpath at compile time instead of enforcing use of LD_LIBRARY_PATH on Linux (linking issue).
* Fix pretty-printing of negative nans on Linux.
* Support for control of printing depth and string printing cutoff (throug flags `pretty_depth` and `pretty_string_size`.
* support for multiple concurrent REPL sessions.

.github/workflows/main.yml

@@ -124,6 +124,7 @@ jobs:
           make -C test test_mlkit
           make -C test test_mlkit_no_gc
           make -C test/explicit_regions all
+          make -C test/repl all
           make -C test/parallelism all
 
       - name: Configure SmlToJs

basis/Real.sml

@@ -22,9 +22,17 @@ structure Real : REAL =
 
     fun (x:real) / (y:real) : real = prim ("divFloat", (x, y))
     fun rem (x:real, y:real) : real = prim ("remFloat", (x, y))
-    fun to_string_gen (s : string) (x : real) : string =
-        prim ("generalStringOfFloat", (s,x))
-    fun toString (x:real) : string = prim ("stringOfFloat", x)
+
+    local
+      fun repair_negnan (s:string) : string =
+          if s = "~nan" then "nan" else s
+    in
+      fun to_string_gen (s : string) (x : real) : string =
+          repair_negnan (prim ("generalStringOfFloat", (s,x)))
+      fun toString (x:real) : string =
+          repair_negnan (prim ("stringOfFloat", x))
+    end
+
     fun sub_unsafe (s:string, i:int) : char = prim ("__bytetable_sub", (s,i))
     fun isNan (x:real) : bool = prim ("isnanFloat", x)
 

basis/basis.mlb

@@ -68,7 +68,7 @@ local
 
     basis Word =
        let open General String IntInfRep
-           basis W = bas WORD.sig Word.sml Word64.sml Word63.sml Word32.sml Word31.sml Word8.sml
+           basis W = bas WORD.sig Word.sml Word64.sml (*Word63.sml*) Word32.sml Word31.sml Word8.sml
                          ann safeLinkTimeElimination
                          in local WordN.sml
                             in Word16.sml

basis/io/text-io.sig

@@ -100,11 +100,15 @@ necessary until one of these conditions holds.  (This is the behaviour
 of the `input' function prescribed in the 1990 Definition of Standard
 ML).
 
-[inputLine istr] returns one line of text, including the terminating
-newline character.  If end of stream is reached before a newline
-character, then the remaining part of the stream is returned, with a
-newline character added.  If istr is at end of stream or is closed,
-then the empty string "" is returned.
+[inputLine istr] returns SOME(ln), where ln is the next line of input
+in the stream strm. Specifically, ln returns all characters from the
+current position up to and including the next newline (#"\n")
+character. If it detects an end-of-stream before the next newline, it
+returns the characters read appended with a newline. Thus, ln is
+guaranteed to always be new-line terminated (and thus nonempty). If
+the current stream position is the end-of-stream, then it returns
+NONE. It raises Size if the length of the line exceeds the length of
+the longest string.
 
 [endOfStream istr] returns false if any elements are available in
 istr; returns true if istr is at end of stream or closed; blocks if

basis/repl.mlb

@@ -0,0 +1,2 @@
+basis.mlb
+repl.sml