遠藤です。

1.9 では正規表現で名前を使った参照ができるので、sprintf でも
名前を使った参照ができると便利じゃないでしょうか。


$ ./ruby -e 'puts "%<foo>d : %<bar>f" % { :foo => 1, :bar => 2 }'
1 : 2.000000

$ ./ruby -e 'printf("%<foo>d : %<bar>f\n", :foo => 1, :bar => 2)'
1 : 2.000000


あまりテストしていませんが、たたき台の実装です。


Index: sprintf.c
===================================================================
--- sprintf.c	(revision 18638)
+++ sprintf.c	(working copy)
@@ -103,18 +103,28 @@
 } while (0)

 #define GETARG() (nextvalue != Qundef ? nextvalue : \
-    posarg < 0 ? \
+    posarg == -1 ? \
     (rb_raise(rb_eArgError, "unnumbered(%d) mixed with numbered",
nextarg), 0) : \
+    posarg == -2 ? \
+    (rb_raise(rb_eArgError, "unnumbered(%d) mixed with named", nextarg), 0) : \
     (posarg = nextarg++, GETNTHARG(posarg)))

 #define GETPOSARG(n) (posarg > 0 ? \
     (rb_raise(rb_eArgError, "numbered(%d) after unnumbered(%d)", n,
posarg), 0) : \
+    posarg == -2 ? \
+    (rb_raise(rb_eArgError, "numbered(%d) after named", n), 0) : \
     ((n < 1) ? (rb_raise(rb_eArgError, "invalid index - %d$", n), 0) : \
 	       (posarg = -1, GETNTHARG(n))))

 #define GETNTHARG(nth) \
     ((nth >= argc) ? (rb_raise(rb_eArgError, "too few arguments"), 0)
: argv[nth])

+#define GETNAMEARG(id) (posarg > 0 ? \
+    (rb_raise(rb_eArgError, "named after unnumbered(%d)", posarg), 0) : \
+    posarg == -1 ? \
+    (rb_raise(rb_eArgError, "named after numbered"), 0) : \
+    rb_hash_aref(get_hash(&hash, argc, argv), id))
+
 #define GETNUM(n, val) \
     for (; p < end && rb_enc_isdigit(*p, enc); p++) {	\
 	int next_n = 10 * n + (*p - '0'); \
@@ -141,7 +151,22 @@
     val = NUM2INT(tmp); \
 } while (0)

+static VALUE
+get_hash(volatile VALUE *hash, int argc, const VALUE *argv)
+{
+    VALUE tmp;

+    if (*hash != Qundef) return *hash;
+    if (argc != 2) {
+	rb_raise(rb_eArgError, "one hash required");
+    }
+    tmp = rb_check_convert_type(argv[1], T_HASH, "Hash", "to_hash");
+    if (NIL_P(tmp)) {
+	rb_raise(rb_eArgError, "one hash required");
+    }
+    return (*hash = tmp);
+}
+
 /*
  *  call-seq:
  *     format(format_string [, arguments...] )   => string
@@ -412,6 +437,7 @@
     VALUE nextvalue;
     VALUE tmp;
     VALUE str;
+    volatile VALUE hash = Qundef;

 #define CHECK_FOR_WIDTH(f)				 \
     if ((f) & FWIDTH) {					 \
@@ -513,6 +539,22 @@
 	    flags |= FWIDTH;
 	    goto retry;

+	  case '<':
+	    {
+		const char *start = p;
+		ID id;
+		for (; p < end && *p != '>'; ) {
+		    p += rb_enc_mbclen(p, end, enc);
+		}
+		if (p >= end) {
+		    rb_raise(rb_eArgError, "malformed name - unmatched parenthesis");
+		}
+		id = rb_intern3(start + 1, p - start - 1, enc);
+		nextvalue = GETNAMEARG(ID2SYM(id));
+		p++;
+		goto retry;
+	    }
+
 	  case '*':
 	    CHECK_FOR_WIDTH(flags);
 	    flags |= FWIDTH;

-- 
Yusuke ENDOH <mame / tsg.ne.jp>