string-to-number

string-to-number

[Nick Roberts]

Currently string-to-number gives 0 for a non-number:

(string-to-number "a")^J
0

but 

(string-to-number "0")^J
0

gives the same result.  So what is a simple test for whether a string
represents a number or not?

If there isn't one,  how about:

(string-to-number "a")^J
nil

Of course this means an error is generated if you try to do arithmetic with a
non-number, but I think that this is appropriate and preferable to taking a
value of 0.


Nick


*** data.c	31 Oct 2005 00:56:53 +1300	1.256
--- data.c	17 Nov 2005 16:28:28 +1300	
***************
*** 2466,2472 ****
    register unsigned char *p;
    register int b;
    int sign = 1;
!   Lisp_Object val;
  
    CHECK_STRING (string);
  
--- 2466,2472 ----
    register unsigned char *p;
    register int b;
    int sign = 1;
!   Lisp_Object val = Qnil;
  
    CHECK_STRING (string);
  
***************
*** 2506,2514 ****
  	  if (digit < 0)
  	    break;
  	  v = v * b + digit;
  	}
  
!       val = make_fixnum_or_float (sign * v);
      }
  
    return val;
--- 2506,2515 ----
  	  if (digit < 0)
  	    break;
  	  v = v * b + digit;
+ 	  val = Qt;
  	}
  
!       if (!NILP (val)) val = make_fixnum_or_float (sign * v);
      }
  
    return val;

Re: string-to-number

[Richard M. Stallman]

Let's not change this.

Re: string-to-number

[Nick Roberts]

 > Let's not change this.

Before the release?  Ever?  Don't you think it's an improvement?  Are you
concerned about backward compatibility?  Are there other reasons?

Nick

Re: string-to-number

[Richard M. Stallman]

     > Let's not change this.

    Before the release?  Ever?  Don't you think it's an improvement?  Are you
    concerned about backward compatibility?  Are there other reasons?

I can't afford to spend time thinking about minor issues, and I don't
want them causing any trouble, so I made a quick simple decision: we
will keep this unchanged.  Would you please let it drop?

There are two kinds of changes we should consider now:

1. Bug fixes.

2. Changes in new features, to get them right the first
time they are released.

Please don't propose other kinds of changes.  It would be ideal not to
even mention issues other than those two categories.