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Re^5: Binary to decimal conversion

by Fletch (Chancellor)
on Dec 11, 2007 at 13:43 UTC ( #656405=note: print w/ replies, xml ) Need Help??


in reply to Re^4: Binary to decimal conversion
in thread Binary to decimal conversion

Erm . . . a LIST may consist of a single scalar value. That single scalar value is concatenated with all the other elements in the LIST (very quickly, obviously, since they're non-existent) and the bytes in that concatenated string (i.e. the single scalar argument) are returned in reverse order, just like the docs say.

The cake is a lie.
The cake is a lie.
The cake is a lie.


Comment on Re^5: Binary to decimal conversion
Re^6: Binary to decimal conversion
by andreas1234567 (Vicar) on Dec 11, 2007 at 13:57 UTC
    Then tell me why this prints hello and not olleh?
    $ perl -wle 'print reverse(q{hello})' hello
    --
    Andreas

      Because print takes a LIST and hence provides a list context to reverse which triggers the list context behavior from the latter (and a 1 element list reversed is indistinguishable from the original 1 element list for obvious reasons). Stick a scalar in there after the print, and/or store the reverse into a scalar temporary variable, and you'll see the behavior you're expecting.

      The cake is a lie.
      The cake is a lie.
      The cake is a lie.

        Said code (and then some):
        $\ = "\n"; print(my @a = reverse('hello')); # hello (order or scalars reversed) print(my $s = reverse('hello')); # olleh (order of chars reversed) print(reverse('hello')); # hello (order or scalars reversed) print(scalar(reverse('hello'))); # olleh (order of chars reversed) sub f(@) { return @_; } sub g($) { return @_; } print(f(reverse('hello')); # hello (order or scalars reversed) print(g(reverse('hello'))); # olleh (order of chars reversed)
      Because you did not RTFM :)
      reverse LIST In list context, returns a list value consisting of the elemen +ts of LIST in the opposite order. In scalar context, concatenates the elements of LIST and returns a string value with all characters in the opposite order. print reverse <>; # line tac, last line first undef $/; # for efficiency of <> print scalar reverse <>; # character tac, last line tsr +if Used without arguments in scalar context, reverse() reverses $ +_. This operator is also handy for inverting a hash, although the +re are some caveats. If a value is duplicated in the original has +h, only one of those can be represented as a key in the inverted hash. Also, this has to unwind one hash and build a whole new one, which may take some time on a large hash, such as from a DBM file. %by_name = reverse %by_address; # Invert the hash

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