[m-rev.] for review: Document what whitespace means to library predicates.

[Peter Wang]

library/char.m:
    Present list of whitespace characters for char.whitespace
    in tabular form.

library/io.m:
library/lexer.m:
library/pprint.m:
library/stream.m:
library/string.m:
    Mention char.is_whitespace in the documentation of predicates which
    use that definition of whitespace characters.

    Module qualify some calls to char.is_whitespace for clarity.
---
 library/char.m   | 10 ++++++++--
 library/io.m     | 10 ++++++++--
 library/lexer.m  |  6 ++++++
 library/pprint.m |  3 +++
 library/stream.m |  5 +++--
 library/string.m | 23 +++++++++++++----------
 6 files changed, 41 insertions(+), 16 deletions(-)

diff --git a/library/char.m b/library/char.m
index b402784c5..9900ad5cc 100644
--- a/library/char.m
+++ b/library/char.m
@@ -118,8 +118,14 @@
     %
 :- pred is_ascii(char::in) is semidet.
 
-    % True iff the character is a whitespace character in the ASCII range,
-    % i.e. a space, tab, newline, carriage return, form-feed, or vertical tab.
+    % True iff the character is a whitespace character in the ASCII range:
+    %
+    %   U+0020  space
+    %   U+0009  tab
+    %   U+000A  line feed
+    %   U+000B  vertical tab
+    %   U+000C  form feed
+    %   U+000D  carriage return
     %
 :- pred is_whitespace(char::in) is semidet.
 
diff --git a/library/io.m b/library/io.m
index 108d12b26..3aaa67359 100644
--- a/library/io.m
+++ b/library/io.m
@@ -141,6 +141,9 @@
     % Read a whitespace delimited word from the current input stream
     % or from the specified stream.
     %
+    % See `char.is_whitespace' for the definition of whitespace characters
+    % used by this predicate.
+    %
 :- pred read_word(io.result(list(char))::out, io::di, io::uo) is det.
 :- pred read_word(io.text_input_stream::in, io.result(list(char))::out,
     io::di, io::uo) is det.
@@ -318,6 +321,9 @@
     % - If it encounters an I/O error, then it also returns
     %   `error(Message, LineNumber)'.
     %
+    % See `char.is_whitespace' for the definition of whitespace characters
+    % used by this predicate.
+    %
 :- pred read(io.read_result(T)::out, io::di, io::uo) is det.
 :- pred read(io.text_input_stream::in, io.read_result(T)::out,
     io::di, io::uo) is det.
@@ -345,8 +351,8 @@
 :- pred read_from_string(string::in, string::in, int::in,
     read_result(T)::out, posn::in, posn::out) is det.
 
-    % Discards all the whitespace from the current stream
-    % or from the specified stream.
+    % Discards all the whitespace characters satisfying `char.is_whitespace'
+    % from the current stream or from the specified stream.
     %
 :- pred ignore_whitespace(io.result::out, io::di, io::uo) is det.
 :- pred ignore_whitespace(io.text_input_stream::in, io.result::out,
diff --git a/library/lexer.m b/library/lexer.m
index 8ff116784..804be60d9 100644
--- a/library/lexer.m
+++ b/library/lexer.m
@@ -89,6 +89,9 @@
     % Keep reading until we encounter either an `end' token
     % (i.e. a full stop followed by whitespace) or the end-of-file.
     %
+    % See `char.is_whitespace' for the definition of whitespace characters
+    % used by this predicate.
+    %
 :- pred get_token_list(token_list::out, io::di, io::uo) is det.
 :- pred get_token_list(io.text_input_stream::in, token_list::out,
     io::di, io::uo) is det.
@@ -107,6 +110,9 @@
     % Return the tokens scanned in Tokens, and return the position one
     % character past the end of the last token in FinalPos.
     %
+    % See `char.is_whitespace' for the definition of whitespace characters
+    % used by this predicate.
+    %
 :- pred string_get_token_list_max(string::in, offset::in, token_list::out,
     posn::in, posn::out) is det.
 
diff --git a/library/pprint.m b/library/pprint.m
index c39fab751..c24637cb4 100644
--- a/library/pprint.m
+++ b/library/pprint.m
@@ -340,6 +340,9 @@
     % Performs word wrapping at the end of line, taking whitespace sequences
     % as delimiters separating words.
     %
+    % See `char.is_whitespace' for the definition of whitespace characters
+    % used by this predicate.
+    %
 :- func word_wrapped(string) = doc.
 
     % Convert arbitrary terms to docs. This requires std_util.functor/3 to work
diff --git a/library/stream.m b/library/stream.m
index 92d68338c..7fb206199 100644
--- a/library/stream.m
+++ b/library/stream.m
@@ -341,7 +341,8 @@
 % Misc. operations on input streams.
 %
 
-    % Discard all the whitespace from the specified stream.
+    % Discard all the whitespace characters satisfying `char.is_whitespace'
+    % from the specified stream.
     %
 :- pred ignore_whitespace(Stream::in, result(Error)::out,
     State::di, State::uo)
@@ -456,7 +457,7 @@ ignore_whitespace(Stream, Result, !State) :-
         Result = eof
     ;
         CharResult = ok(Char),
-        ( if is_whitespace(Char) then
+        ( if char.is_whitespace(Char) then
             ignore_whitespace(Stream, Result, !State)
         else
             unget(Stream, Char, !State),
diff --git a/library/string.m b/library/string.m
index 2a6071da7..67ffa342b 100644
--- a/library/string.m
+++ b/library/string.m
@@ -854,22 +854,22 @@
 
     % strip(String):
     %
-    % Returns `String' minus any initial and trailing whitespace characters
-    % in the ASCII range.
+    % Returns `String' minus any initial and trailing ASCII whitespace
+    % characters, i.e. characters satisfying `char.is_whitespace'.
     %
 :- func strip(string) = string.
 
     % lstrip(String):
     %
-    % Return `String' minus any initial whitespace characters
-    % in the ASCII range.
+    % Return `String' minus any initial ASCII whitespace characters,
+    % i.e. characters satisfying `char.is_whitespace'.
     %
 :- func lstrip(string) = string.
 
     % rstrip(String):
     %
-    % Returns `String' minus any trailing whitespace characters
-    % in the ASCII range.
+    % Returns `String' minus any trailing ASCII whitespace characters,
+    % i.e. characters satisfying `char.is_whitespace'.
     %
 :- func rstrip(string) = string.
 
@@ -914,6 +914,9 @@
     % it will be broken over two (or more) lines. Sequences of whitespace
     % characters are replaced by a single space.
     %
+    % See `char.is_whitespace' for the definition of whitespace characters
+    % used by this predicate.
+    %
 :- func word_wrap(string, int) = string.
 
     % word_wrap_separator(Str, N, WordSeparator) = Wrapped:
@@ -4896,13 +4899,13 @@ chomp(S) = Chomp :-
     ).
 
 strip(S0) = S :-
-    L = prefix_length(is_whitespace, S0),
-    R = suffix_length(is_whitespace, S0),
+    L = prefix_length(char.is_whitespace, S0),
+    R = suffix_length(char.is_whitespace, S0),
     S = between(S0, L, length(S0) - R).
 
-lstrip(S) = lstrip_pred(is_whitespace, S).
+lstrip(S) = lstrip_pred(char.is_whitespace, S).
 
-rstrip(S) = rstrip_pred(is_whitespace, S).
+rstrip(S) = rstrip_pred(char.is_whitespace, S).
 
 lstrip_pred(P, S) = right(S, length(S) - prefix_length(P, S)).
 
-- 
2.14.1