Impelement derivative-based regular expressions.

1 files changed, 7 insertions, 7 deletions

diff --git a/parser.y b/parser.y
index cc0815c8..57692704 100644
--- a/parser.y
+++ b/parser.y
@@ -453,17 +453,17 @@ regex : '/' regexpr '/'         { $$ = $2; }
                                   yybadtoken(yychar, lit("regex")); }
       ;
 
-regexpr : regbranch                     { $$ = $1; }
-        | regexpr '|' regexpr           { $$ = list(list(or_s, $1,
-                                                         $3, nao), nao); }
-        | regexpr '&' regexpr           { $$ = list(list(and_s, $1,
-                                                         $3, nao), nao); }
+regexpr : regbranch                     { $$ = if3(cdr($1), 
+                                                   cons(compound_s, $1),
+                                                   car($1)); }
+        | regexpr '|' regexpr           { $$ = list(or_s, $1, $3, nao); }
+        | regexpr '&' regexpr           { $$ = list(and_s, $1, $3, nao); }
+        | '~' regexpr                   { $$ = list(compl_s, $2, nao); }
         | /* empty */                   { $$ = nil; }
         ;
 
 regbranch : regterm             { $$ = cons($1, nil); }
           | regterm regbranch   { $$ = cons($1, $2); }
-          | '~' regbranch       { $$ = cons(cons(compl_s, $2), nil); }
           ;
 
 regterm : '[' regclass ']'      { $$ = cons(set_s, $2); }
@@ -476,7 +476,7 @@ regterm : '[' regclass ']'      { $$ = cons(set_s, $2); }
         | regterm '+'           { $$ = list(oneplus_s, $1, nao); }
         | regterm '?'           { $$ = list(optional_s, $1, nao); }
         | REGCHAR               { $$ = chr($1); }
-        | '(' regexpr ')'       { $$ = cons(compound_s, $2); }
+        | '(' regexpr ')'       { $$ = $2; }
         | '(' error             { $$ = nil;
                                   yybadtoken(yychar,
                                              lit("regex subexpression")); }