Add hide combinator

extra/peg/peg-docs.factor

@@ -128,3 +128,13 @@ HELP: sp
 { $description 
     "Returns a parser that calls the original parser 'p1' after stripping any whitespace "
     " from the left of the input string." } ;
+
+HELP: hide
+{ $values 
+  { "p1" "a parser" } 
+  { "parser" "a parser" } 
+}
+{ $description 
+    "Returns a parser that succeeds if the original parser succeeds, but does not " 
+    "put any result in the AST. Useful for ignoring 'syntax' in the AST." }
+{ $example "\"[\" token hide number \"]\" token hide 3array seq" } ;

extra/peg/peg-tests.factor

@@ -144,4 +144,21 @@ IN: temporary
 
 { CHAR: a } [ 
   "a" [ CHAR: a = ] satisfy parse parse-result-ast
-] unit-test
+] unit-test
+
+{ "a" } [
+  "    a" "a" token sp parse parse-result-ast
+] unit-test
+
+{ "a" } [
+  "a" "a" token sp parse parse-result-ast
+] unit-test
+
+{ V{ "a" } } [
+  "[a]" "[" token hide "a" token "]" token hide 3array seq parse parse-result-ast
+] unit-test
+
+{ f } [
+  "a]" "[" token hide "a" token "]" token hide 3array seq parse 
+] unit-test
+

extra/peg/peg.factor

@@ -205,3 +205,6 @@ PRIVATE>
 
 : sp ( parser -- parser )
   sp-parser construct-boa init-parser ;
+
+: hide ( parser -- parser )
+  [ drop ignore ] action ;