From: Sean Chittenden <sean@...>
Date: 2002-04-24T14:24:44+09:00
Subject: Numberic#prev


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I do a lot of incrementing and decrementing of values: it'd be nice if
Numeric#succ had a counter part.

The attached patch provides Numeric#prev which is faster in tight
loops than (one less object):

i = 10
p i.prev

-sc

PS Let me know if anyone has any interest in an inline
increment/decrement library.

i = 1
i.incr
p i    >> 2
i.decr
p i    >> 1

-- 
Sean Chittenden

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Index: numeric.c
===================================================================
RCS file: /src/ruby/numeric.c,v
retrieving revision 1.44
diff -u -r1.44 numeric.c
--- numeric.c	2002/04/24 05:08:04	1.44
+++ numeric.c	2002/04/24 05:20:55
@@ -1024,6 +1024,17 @@
 }
 
 static VALUE
+int_prev(num)
+    VALUE num;
+{
+    if (FIXNUM_P(num)) {
+	long i = FIX2LONG(num) - 1;
+	return rb_int2inum(i);
+    }
+    return rb_funcall(num, '-', 1, INT2FIX(1));
+}
+
+static VALUE
 int_chr(num)
     VALUE num;
 {
@@ -1652,6 +1663,7 @@
     rb_include_module(rb_cInteger, rb_mPrecision);
     rb_define_method(rb_cInteger, "succ", int_succ, 0);
     rb_define_method(rb_cInteger, "next", int_succ, 0);
+    rb_define_method(rb_cInteger, "prev", int_prev, 0);
     rb_define_method(rb_cInteger, "chr", int_chr, 0);
     rb_define_method(rb_cInteger, "to_i", int_to_i, 0);
     rb_define_method(rb_cInteger, "to_int", int_to_i, 0);

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