The Inbox: Collections-hk.360.mcz

A new version of Collections was added to project The Inbox:
http://source.squeak.org/inbox/Collections-hk.360.mcz

==================== Summary ====================

Name: Collections-hk.360
Author: hk
Time: 20 May 2010, 9:04:53.211 am
UUID: 75c4bea4-ca87-3a40-8a74-e89fc5b7b750
Ancestors: Collections-ul.359

changed String isAllDigits to return false on empty strings

=============== Diff against Collections-ul.359 ===============

Item was changed:
  ----- Method: String>>isAllDigits (in category 'testing') -----
  isAllDigits
+ "whether the receiver is composed entirely of digits and has at least one digit"
- "whether the receiver is composed entirely of digits"
  self do: [:c | c isDigit ifFalse: [^ false]].
+ self ifEmpty: [^false].
  ^ true!

On 2010/05/20 07:05, [hidden email] wrote:
Isn't the problem that the caller wants to know that some string
contains a number (in base 10, presumably)?

It seems perfectly sensible that '' isAllDigits returns true - because
it's vacuously true.

So shouldn't there be (and I haven't looked for existing functionality)
something like String>>isNumeric which says self isEmpty and: [self
isAllDigits] ?

I'm torn between my sense of logic and my desire to avoid bikeshedding.

frank

Hello Frank,


FS> Isn't the problem that the caller wants to know that some string
FS> contains a number (in base 10, presumably)?

no, it's deeper, a number may have sign, decimal separator .....

FS> It seems perfectly sensible that '' isAllDigits returns true - because
FS> it's vacuously true.

The change arose from the fact that I have written:

(aString notEmpty and: [aString isAllDigits]) if True: []

in various applications for e.g. 10 being valid for 10 o'clock or -,4
being a valid float.

FS> So shouldn't there be (and I haven't looked for existing functionality)
FS> something like String>>isNumeric which says self isEmpty and: [self
FS> isAllDigits] ?

Something like that would be my next resort, but "isNumeric" is
misleading as it's also true for '-3'.

FS> I'm torn between my sense of logic and my desire to avoid bikeshedding.

The reason to discuss it is, it might break existing code. My logic
would be that isAllDigits is a pointed form of isDigits and
'' isDigits is undoubtedly false (or so I hope).

At least I found a good name if I have to add yet another method to
String.



Cheers,

Herbert

On 5/20/2010 11:29 AM, Herbert König wrote:
Yeah, it's an interesting semantic difference. Do we mean the method to
imply that "each character is a digit" (false for an empty string) or do
we mean "there are no non-digits characters in it" (true for an empty
string). I would lean towards the former but the argument for the latter
can certainly be made.

Cheers,
   - Andreas