[ruby-dev:19261] lstripped here-document (Re: comments and continuing strings on the next line)

なかだです。

At Tue, 17 Sep 2002 22:52:00 +0900,
Paul Brannan wrote:
> I do recall one of the apocalypses mentioning a perl rfc that proposed a
> <<< operator for 'here documents', which would remove whitespace from
> the 'here document' (at compile-time) that matched the whitespace in
> front of the terminator.  Doesn't seem like a bad idea for either perl
> or ruby.

しばらく前のruby-coreの話ですが、こういうのはどうでしょうか。

    p <<-|EOS
      |  foo
      |    bar
    EOS
    # => "  foo\n    bar\n"

つまり、<<-とterminatorの間にクォーテーション以外の記号があった場合、
行頭の空白とその記号までを削除します。その記号がなければエラーです。


Index: parse.y
===================================================================
RCS file: /cvs/ruby/src/ruby/parse.y,v
retrieving revision 1.239
diff -u -2 -p -r1.239 parse.y
--- parse.y	30 Dec 2002 22:56:21 -0000	1.239
+++ parse.y	1 Jan 2003 00:49:46 -0000
@@ -2859,4 +2859,5 @@ regx_options()
 #define STR_FUNC_SYMBOL 0x10
 #define STR_FUNC_INDENT 0x20
+#define STR_FUNC_LSTRIP 0x40
 
 enum string_type {
@@ -3020,4 +3021,5 @@ heredoc_identifier()
 {
     int c = nextc(), term, func = 0, len;
+    unsigned char margin = 0;
 
     if (c == '-') {
@@ -3025,4 +3027,5 @@ heredoc_identifier()
 	func = STR_FUNC_INDENT;
     }
+  again:
     switch (c) {
       case '\'':
@@ -3048,4 +3051,10 @@ heredoc_identifier()
       default:
 	if (!is_identchar(c)) {
+	    if (!margin && (func & STR_FUNC_INDENT) && ISPRINT(c) && !isspace(c)) {
+		func |= STR_FUNC_LSTRIP;
+		margin = (unsigned char)c;
+		c = nextc();
+		goto again;
+	    }
 	    pushback(c);
 	    if (func & STR_FUNC_INDENT) {
@@ -3065,4 +3074,5 @@ heredoc_identifier()
     }
 
+    if (margin) tokadd(margin);
     tokfix();
     len = lex_p - lex_pbeg;
@@ -3101,5 +3111,5 @@ whole_match_p(eos, len, indent)
 	while (*p && ISSPACE(*p)) p++;
     }
-    n= lex_pend - (p + len);
+    n = lex_pend - (p + len);
     if (n < 0 || n > 0 && p[len] != '\n' && p[len] != '\r') return Qfalse;
     if (strncmp(eos, p, len) == 0) return Qtrue;
@@ -3112,5 +3122,5 @@ here_document(here)
 {
     int c, func, indent = 0;
-    char *eos, *p, *pend;
+    char *eos, *p, *pend, margin = 0;
     long len;
     VALUE str = 0;
@@ -3119,4 +3129,5 @@ here_document(here)
     len = RSTRING(here->nd_lit)->len - 1;
     indent = (func = *eos++) & STR_FUNC_INDENT;
+    if (func & STR_FUNC_LSTRIP) margin = eos[--len];
 
     if ((c = nextc()) == -1) {
@@ -3136,4 +3147,11 @@ here_document(here)
 	    p = RSTRING(lex_lastline)->ptr;
 	    pend = lex_pend;
+	    if (margin) {
+		while ((c = *p) == ' ' || c == '\t') p++;
+		if (margin && *p++ != margin) {
+		    lex_p = p;
+		    goto no_margin;
+		}
+	    }
 	    if (pend > p) {
 		switch (pend[-1]) {
@@ -3173,5 +3191,11 @@ here_document(here)
 	}
 	do {
-	    pushback(c);
+	    if (margin && was_bol()) {
+		while (c == ' ' || c == '\t') c = nextc();
+		if (margin && c != margin) goto no_margin;
+	    }
+	    else {
+		pushback(c);
+	    }
 	    if ((c = tokadd_string(func, '\n', 0)) == -1) goto error;
 	    if (c != '\n') {
@@ -3188,4 +3212,15 @@ here_document(here)
     yylval.node = NEW_STR(str);
     return tSTRING_CONTENT;
+
+  no_margin:
+    {
+	char buf[40];
+	sprintf(buf, "can't find left margin character \"%c\"", margin);
+	--lex_p;
+	yyerror(buf);
+	heredoc_restore(lex_strterm);
+	lex_strterm = 0;
+	return 0;
+    }
 }
 


-- 
--- 僕の前にBugはない。
--- 僕の後ろにBugはできる。
    中田 伸悦