How Well Can You Read Documentation?

Posted on 28 March, 201228 September, 2014 by Dave Cross

(I was going to call this post “How well do you understand context?” but I think this title is more accurate).

I just saw someone recommending this code:

$reversed = reverse(split //, $string);

1	$reversed = reverse(split //, $string);

Looks sensible enough, doesn’t it? But it isn’t. What’s the hidden inefficiency?

7 thoughts on “How Well Can You Read Documentation?”

David Dorward says:

28 March, 2012 at 12:09

And now I’ve learned something new about reverse. Hooray for DWIM.

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Lars Balker says:

28 March, 2012 at 15:39

Huh.

I don’t think that’s a sane behaviour for reverse in scalar context (only ever used it with a single argument in scalar context), but I’ll be damned if I can come up with a better alternative.

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Conor says:

29 March, 2012 at 15:20

Why not just: $reversed = scalar reverse $string; ?

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1. Dave Cross says:
  
  29 March, 2012 at 15:23
  
  Well, quite.
  
  Although your call to scalar is unnecessary.
  
  Reply
  1. Ludo says:
    
    24 May, 2012 at 03:01
    
    Why does reverse $string return the original string, but an assignment e.g. : $reversed = reverse $string store the reversed string in the lvalue?
    
    Reply
    1. Dave Cross says:
      
      24 May, 2012 at 15:20
      
      As the title implies, read the documentation.
      
      Reply
jvector says:

18 June, 2012 at 15:03

late joining the party. SOme of these ‘dwimminess’ features make me a bit uncomfortable. I feel that if c gives me ‘fred’ then maybe it’s not very /useful/, but at least it’s consistent with my simple user model of the language. When convenience measures like making that result be ‘derf’ are mixed into the language, then it seems to me kind of like encountering an irregular verb in a natural language: it may make life easier on this one occasion for somebody but the whole edifice gets just a bit more complicated … adding to the meme that Perl is ‘too hard’.

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