* Replaced the SDF parser by a substantially faster Bison/Flex

parser (roughly 80x faster).

  The absolutely latest version of Bison (1.875c) is required for
  reentrant GLR support, as well as a recent version of Flex (say,
  2.5.31).  Note that most Unix distributions ship with the
  prehistoric Flex 2.5.4, which doesn't support reentrancy.

src/libexpr/parser.y

@@ -0,0 +1,128 @@
+%glr-parser
+%pure-parser
+%locations
+%error-verbose
+%parse-param { yyscan_t scanner }
+%parse-param { void * data }
+%lex-param { yyscan_t scanner }
+
+%{
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <aterm2.h>
+
+#include "parser-tab.h"
+#include "lexer-tab.h"
+
+void setParseResult(void * data, ATerm t);
+void parseError(void * data, char * error, int line, int column);
+ATerm absParsedPath(void * data, ATerm t);
+
+void yyerror(YYLTYPE * loc, yyscan_t scanner, void * data, char * s)
+{
+    parseError(data, s, loc->first_line, loc->first_column);
+}
+ 
+%}
+
+%union {
+  ATerm t;
+  ATermList ts;
+}
+
+%type <t> start expr expr_function expr_assert expr_op
+%type <t> expr_app expr_select expr_simple bind formal
+%type <ts> binds expr_list formals
+%token <t> ID INT STR PATH URI
+%token IF THEN ELSE ASSERT LET REC EQ NEQ AND OR IMPL
+
+%nonassoc IMPL
+%left OR
+%left AND
+%nonassoc EQ NEQ
+%left NEG
+
+%%
+
+start: expr { setParseResult(data, $1); };
+
+expr: expr_function;
+
+expr_function
+  : '{' formals '}' ':' expr_function
+    { $$ = ATmake("Function(<term>, <term>)", $2, $5); }
+  | expr_assert
+  ;
+
+expr_assert
+  : ASSERT expr ';' expr_assert
+    { $$ = ATmake("Assert(<term>, <term>)", $2, $4); }
+  | expr_op
+  ;
+
+expr_op
+  : '!' expr_op %prec NEG { $$ = ATmake("OpNot(<term>)", $2); }
+  | expr_op EQ expr_op { $$ = ATmake("OpEq(<term>, <term>)", $1, $3); }
+  | expr_op NEQ expr_op { $$ = ATmake("OpNEq(<term>, <term>)", $1, $3); }
+  | expr_op AND expr_op { $$ = ATmake("OpAnd(<term>, <term>)", $1, $3); }
+  | expr_op OR expr_op { $$ = ATmake("OpOr(<term>, <term>)", $1, $3); }
+  | expr_op IMPL expr_op { $$ = ATmake("OpImpl(<term>, <term>)", $1, $3); }
+  | expr_app
+  ;
+
+expr_app
+  : expr_app expr_select
+    { $$ = ATmake("Call(<term>, <term>)", $1, $2); }
+  | expr_select { $$ = $1; }
+  ;
+
+expr_select
+  : expr_select '.' ID
+    { $$ = ATmake("Select(<term>, <term>)", $1, $3); }
+  | expr_simple { $$ = $1; }
+  ;
+
+expr_simple
+  : ID { $$ = ATmake("Var(<term>)", $1); }
+  | STR { $$ = ATmake("Str(<term>)", $1); }
+  | PATH { $$ = ATmake("Path(<term>)", absParsedPath(data, $1)); }
+  | URI { $$ = ATmake("Uri(<term>)", $1); }
+  | '(' expr ')' { $$ = $2; }
+  | LET '{' binds '}' { $$ = ATmake("LetRec(<term>)", $3); }
+  | REC '{' binds '}' { $$ = ATmake("Rec(<term>)", $3); }
+  | '{' binds '}' { $$ = ATmake("Attrs(<term>)", $2); }
+  | '[' expr_list ']' { $$ = ATmake("List(<term>)", $2); }
+  | IF expr THEN expr ELSE expr
+    { $$ = ATmake("If(<term>, <term>, <term>)", $2, $4, $6); }
+  ;
+
+binds
+  : binds bind { $$ = ATinsert($1, $2); }
+  | { $$ = ATempty; }
+  ;
+
+bind
+  : ID '=' expr ';'
+    { $$ = ATmake("Bind(<term>, <term>)", $1, $3); }
+  ;
+
+expr_list
+  : expr_select expr_list { $$ = ATinsert($2, $1); }
+    /* yes, this is right-recursive, but it doesn't matter since
+       otherwise we would need ATreverse which requires unbounded
+       stack space */
+  | { $$ = ATempty; }
+  ;
+
+formals
+  : formal ',' formals { $$ = ATinsert($3, $1); } /* idem - right recursive */
+  | formal { $$ = ATinsert(ATempty, $1); }
+  ;
+
+formal
+  : ID { $$ = ATmake("NoDefFormal(<term>)", $1); }
+  | ID '?' expr { $$ = ATmake("DefFormal(<term>, <term>)", $1, $3); }
+  ;
+  
+%%