[m-rev.] for review: make parsing tail recursive

[Peter Wang]

Estimated hours taken: 0.5
Branches: main

Avoid running out of stack space when parsing big terms.

library/Mercury.options:
	Enable last-call-modulo-cons optimisation to make
	`lexer.get_token_list_2' tail recursive.

library/parser.m:
	Make `check_for_bad_token' tail recursive.

Index: library/Mercury.options
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/library/Mercury.options,v
retrieving revision 1.29
diff -u -r1.29 Mercury.options
--- library/Mercury.options	24 Jan 2008 03:50:46 -0000	1.29
+++ library/Mercury.options	7 May 2008 00:37:32 -0000
@@ -16,6 +16,7 @@
 MCFLAGS-set += $(TYPE_SPEC_FLAGS)
 MCFLAGS-set_ordlist += $(TYPE_SPEC_FLAGS)
 
+MCFLAGS-lexer += --optimize-constructor-last-call
 MCFLAGS-sparse_bitset += --use-atomic-cells --optimize-constant-propagation
 MCFLAGS-tree_bitset += --use-atomic-cells --optimize-constant-propagation
 
Index: library/parser.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/library/parser.m,v
retrieving revision 1.58
diff -u -r1.58 parser.m
--- library/parser.m	3 Apr 2008 05:26:47 -0000	1.58
+++ library/parser.m	7 May 2008 00:37:32 -0000
@@ -251,7 +251,13 @@
 
 :- pred check_for_bad_token(token_list::in, string::out, int::out) is semidet.
 
-check_for_bad_token(token_cons(Token, LineNum, Tokens), Message, LineNum) :-
+check_for_bad_token(Token, Message, LineNum) :-
+    check_for_bad_token_2(Token, Message),
+    Token = token_cons(_, LineNum, _).
+
+:- pred check_for_bad_token_2(token_list::in, string::out) is semidet.
+
+check_for_bad_token_2(token_cons(Token, _LineNum, Tokens), Message) :-
     ( Token = io_error(IO_Error) ->
         io.error_message(IO_Error, IO_ErrorMessage),
         string.append("I/O error: ", IO_ErrorMessage, Message)
@@ -264,7 +270,7 @@
     ; Token = error(ErrorMessage) ->
         string.append("Syntax error: ", ErrorMessage, Message)
     ;
-        check_for_bad_token(Tokens, Message, LineNum)
+        check_for_bad_token_2(Tokens, Message)
     ).
 
 :- pred parse_whole_term(parse(term(T))::out,


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