From e5cd9bbd3de84e90d5602b83a0eb7780ec4b750e Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sat, 14 Dec 2013 23:46:32 -0800
Subject: Support for parsing Lisp expression out of strings and streams. New
 catenated streams make the Yacc hack possible.

* eval.c (eval_init): Register lisp_parse as intrinsic.

* parser.h (lisp_parse): Declared.

* parser.l: New lexical hack to produce SECRET_ESCAPE_E token.
(regex_parse): Move declaration before statements.
(lisp_parse): New function.

* parser.y (SECRET_ESCAPE_E): New token type.
(spec): New production rule for single expression.

* stream.c (cat_stream_print, cat_get_line, cat_get_char,
cat_get_byte, cat_get_prop): New static functions.
(cat_stream_ops): New static function.
(make_catenated_stream): New function.

* stream.h (make_catenated_stream): Declared.
---
 parser.l | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

(limited to 'parser.l')

diff --git a/parser.l b/parser.l
index bdee6275..78e29408 100644
--- a/parser.l
+++ b/parser.l
@@ -682,6 +682,12 @@ UONLY   {U2}{U}|{U3}{U}{U}|{U4}{U}{U}{U}
   return SECRET_ESCAPE_R;
 }
 
+<INITIAL>@\x01E {
+  yy_push_state(SPECIAL);
+  yy_push_state(NESTED);
+  return SECRET_ESCAPE_E;
+}
+
 <INITIAL>^@[#;].*\n {
   /* eat whole line comment */
   lineno++;
@@ -837,10 +843,10 @@ val regex_parse(val string, val error_stream)
 {
   uses_or2;
   val parse_string = cat_str(list(lit("@\x01R"), string, nao), nil);
+  val save_stream = std_error;
   yyin_stream = make_string_byte_input_stream(parse_string);
   errors = 0;
   lineno = 1;
-  val save_stream = std_error;
   std_error = if3(error_stream == t, std_output, or2(error_stream, std_null));
   {
     int gc = gc_state(0);
@@ -854,3 +860,27 @@ val regex_parse(val string, val error_stream)
   std_error = save_stream;
   return errors ? nil : get_spec();
 }
+
+val lisp_parse(val source, val error_stream)
+{
+  uses_or2;
+  val input_stream = if3(stringp(source), make_string_byte_input_stream(source), source);
+  val secret_token_stream = make_string_byte_input_stream(lit("@\x01" "E"));
+  val name = if3(stringp(source),
+                 format(nil, lit("expr: ~s"), source, nao),
+                 stream_get_prop(source, name_k));
+  val save_stream = std_error;
+  yyin_stream = make_catenated_stream(list(secret_token_stream, input_stream, nao));
+  errors = 0;
+  lineno = 1;
+  std_error = if3(error_stream == t, std_output, or2(error_stream, std_null));
+  {
+    int gc = gc_state(0);
+    spec_file_str = if3(std_error != std_null, name, lit(""));
+    yyparse();
+    yylex_destroy();
+    gc_state(gc);
+  }
+  std_error = save_stream;
+  return errors ? nil : get_spec();
+}
-- 
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