From: Florian Frank <flori@...>
Date: 2002-06-24T23:59:04+09:00
Subject: Re: No exceptions from String#to_i

Am 2002-06-24 21:23:58 +0900 schrieb ts:
> >>>>> "N" == Nikodemus Siivola <tsiivola@cc.hut.fi> writes:
> 
> N>  Integer(nil)   == 0
> 
>   nil.to_i is defined
> 
> N>  Integer(false) #-> exception
> 
>  false.to_i is not defined
> 
> N>  Array(foo)   == foo.to_a
> 
>   Well, first ruby look if #to_ary exist and call it otherwise it try to
>   call #to_a
> 
> N>  Integer(foo) != foo.to_i
> N>  Float(foo)   != foo.to_f
> 
>  it depend of foo

There are exceptions to this rule:

Float(nil) => 0.0

object.c:
case T_NIL:
	return rb_float_new(0.0);

But nil.to_f throws an exception because it isn't defined.

Someone posted an RCR on Ruby Garden concerning this issue:
http://www.rubygarden.org/article.php?sid=241

This small patch adds the to_f-method to NilClass:

Index: object.c
===================================================================
RCS file: /src/ruby/object.c,v
retrieving revision 1.79
diff -u -r1.79 object.c
--- object.c    2002/05/21 05:39:19     1.79
+++ object.c    2002/06/24 14:49:46
@@ -338,6 +338,13 @@
 }
 
 static VALUE
+nil_to_f(obj)
+    VALUE obj;
+{
+     return rb_float_new(0.0);
+}
+
+static VALUE
 nil_to_s(obj)
     VALUE obj;
 {
@@ -1072,9 +1079,6 @@
       case T_STRING:
        return rb_float_new(rb_str_to_dbl(val, Qtrue));
 
-      case T_NIL:
-       return rb_float_new(0.0);
-
       default:
        return rb_convert_type(val, T_FLOAT, "Float", "to_f");
     }
@@ -1282,6 +1286,7 @@
 
     rb_cNilClass = rb_define_class("NilClass", rb_cObject);
     rb_define_method(rb_cNilClass, "to_i", nil_to_i, 0);
+    rb_define_method(rb_cNilClass, "to_f", nil_to_f, 0);
     rb_define_method(rb_cNilClass, "to_s", nil_to_s, 0);
     rb_define_method(rb_cNilClass, "to_a", nil_to_a, 0);
     rb_define_method(rb_cNilClass, "inspect", nil_inspect, 0);

I don't know if this breaks any existing code.

-- 
To assert that the earth revolves around the sun is as erroneous as to claim 
that Jesus was not born of a virgin.
  -- Cardinal Bellarmine, "The trial of Galileo", 1615