[m-rev.] for review: add string.line type

[Peter Wang]

Estimated hours taken: 1
Branches: main

Introduce a standard way to read lines efficiently but generically using
stream.get/4.

library/string.m:
	Add the type string.line.

library/io.m:
	Make io.input_stream an instance of stream.reader with unit
	string.line.

compiler/error_util.m:
	Rename error_util.line to error_line to disambiguate it from
	string.line.

extras/net/tcp.m:
	Remove the tcp.line type and use string.line instead.

NEWS:
	Announce the change.


Index: NEWS
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/NEWS,v
retrieving revision 1.453
diff -u -r1.453 NEWS
--- NEWS	12 Apr 2007 04:31:09 -0000	1.453
+++ NEWS	19 Apr 2007 02:13:48 -0000
@@ -137,6 +137,10 @@
 * We have added a function construct.get_functor_lex/2 which converts
   an ordinal functor number into a lexicographic functor number.
 
+* We have added a type `string.line' and made input streams an instance
+  of stream.reader/4 with that unit type.  This means stream.get/4
+  can be used to efficiently read lines.
+
 Changes to the Mercury compiler:
 
 * The compiler now issues a warning when an inst declaration is not
Index: compiler/error_util.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/compiler/error_util.m,v
retrieving revision 1.61
diff -u -r1.61 error_util.m
--- compiler/error_util.m	19 Jan 2007 07:04:11 -0000	1.61
+++ compiler/error_util.m	19 Apr 2007 02:13:48 -0000
@@ -841,7 +841,7 @@
 
 indent_increment = 2.
 
-:- pred write_lines(list(line)::in, maybe(prog_context)::in, int::in,
+:- pred write_lines(list(error_line)::in, maybe(prog_context)::in, int::in,
     io::di, io::uo) is det.
 
 write_lines([], _, _, !IO).
@@ -852,7 +852,7 @@
     ;
         MaybeContext = no
     ),
-    Line = line(LineIndent, LineWords),
+    Line = error_line(LineIndent, LineWords),
     Indent = FixedIndent + LineIndent * indent_increment,
     string.pad_left("", ' ', Indent, IndentStr),
     io.write_string(IndentStr, !IO),
@@ -1158,8 +1158,8 @@
 
 %----------------------------------------------------------------------------%
 
-:- type line
-    --->    line(
+:- type error_line
+    --->    error_line(
                 int,            % Indent level; multiply by indent_increment
                                 % to get number of spaces of indentation.
                 list(string)    % The words on the line.
@@ -1171,7 +1171,7 @@
     % at least one line.
     %
 :- pred group_words(bool::in, int::in, list(paragraph)::in, int::in,
-    list(line)::out) is det.
+    list(error_line)::out) is det.
 
 group_words(IsFirst, CurIndent, Paras, Max, Lines) :-
     (
@@ -1189,7 +1189,7 @@
         ),
         NextIndent = RestIndent + FirstIndentDelta,
 
-        BlankLine = line(CurIndent, []),
+        BlankLine = error_line(CurIndent, []),
         list.duplicate(NumBlankLines, BlankLine, BlankLines),
         (
             FirstParaWords = [],
@@ -1199,7 +1199,7 @@
             FirstParaWords = [FirstWord | LaterWords],
             get_line_of_words(FirstWord, LaterWords, CurIndent, Max,
                 LineWords, RestWords),
-            CurLine = line(CurIndent, LineWords),
+            CurLine = error_line(CurIndent, LineWords),
 
             group_nonfirst_line_words(RestWords, RestIndent, Max,
                 ParaRestLines),
@@ -1211,7 +1211,7 @@
     ).
 
 :- pred group_nonfirst_line_words(list(string)::in, int::in, int::in,
-    list(line)::out) is det.
+    list(error_line)::out) is det.
 
 group_nonfirst_line_words(Words, Indent, Max, Lines) :-
     (
@@ -1221,7 +1221,7 @@
         Words = [FirstWord | LaterWords],
         get_line_of_words(FirstWord, LaterWords, Indent, Max,
             LineWords, RestWords),
-        Line = line(Indent, LineWords),
+        Line = error_line(Indent, LineWords),
         group_nonfirst_line_words(RestWords, Indent, Max, RestLines),
         Lines = [Line | RestLines]
     ).
Index: extras/net/tcp.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/extras/net/tcp.m,v
retrieving revision 1.3
diff -u -r1.3 tcp.m
--- extras/net/tcp.m	18 Apr 2007 05:12:37 -0000	1.3
+++ extras/net/tcp.m	19 Apr 2007 02:13:48 -0000
@@ -17,6 +17,7 @@
 :- interface.
 :- import_module io.
 :- import_module stream.
+:- import_module string.
 
 :- type tcp.
 :- type bound_tcp.
@@ -52,8 +53,6 @@
 
 :- type error.
 
-:- type line ---> line(string).
-
 :- instance stream(tcp, io.state).
 :- instance error(tcp.error).
 
@@ -86,7 +85,6 @@
 :- import_module char.
 :- import_module list.
 :- import_module require.
-:- import_module string.
 
 :- type tcp
 	--->	tcp(
Index: library/io.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/library/io.m,v
retrieving revision 1.378
diff -u -r1.378 io.m
--- library/io.m	30 Mar 2007 03:05:00 -0000	1.378
+++ library/io.m	19 Apr 2007 02:13:48 -0000
@@ -1461,6 +1461,7 @@
 :- instance stream.stream(io.input_stream, io).
 :- instance stream.input(io.input_stream, io, io.error).
 :- instance stream.reader(io.input_stream, char, io, io.error).
+:- instance stream.reader(io.input_stream, line, io, io.error).
 
 :- instance stream.line_oriented(io.input_stream, io).
 :- instance stream.putback(io.input_stream, char, io, io.error).
@@ -9073,6 +9074,24 @@
     )
 ].
 
+:- instance stream.reader(io.input_stream, line, io, io.error)
+    where
+[
+    ( get(Stream, Result, !IO) :-
+        io.read_line_as_string(Stream, Result0, !IO),
+        (
+            Result0 = ok(String),
+            Result = ok(line(String))
+        ;
+            Result0 = eof,
+            Result = eof
+        ;
+            Result0 = error(Error),
+            Result = error(Error)
+        )
+    )
+].
+
 :- instance stream.putback(io.input_stream, char, io, io.error) where
 [
     pred(unget/4) is io.putback_char
Index: library/string.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/library/string.m,v
retrieving revision 1.257
diff -u -r1.257 string.m
--- library/string.m	18 Mar 2007 23:35:00 -0000	1.257
+++ library/string.m	19 Apr 2007 02:13:48 -0000
@@ -40,6 +40,12 @@
 
 %-----------------------------------------------------------------------------%
 
+    % This type is used for defining stream typeclass instances where the raw
+    % string type would be ambiguous.
+    %
+:- type line
+    --->    line(string).
+
     % Determine the length of a string.
     % An empty string has length zero.
     %
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