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Re: Five Ways to Reverse a String of Words (C#, Perl 5, Perl 6, Ruby, Haskell)

by apotheon (Deacon)
on Dec 13, 2006 at 01:48 UTC ( #589472=note: print w/ replies, xml ) Need Help??


in reply to Five Ways to Reverse a String of Words (C#, Perl 5, Perl 6, Ruby, Haskell)

This task gets absurdly easy in UCBLogo (a Logo dialect that is, in effect, an M-expression dialect of Lisp complete with macros). It is, in fact, so easy as to be almost meaningless in the context of UCBLogo. You don't have to create the procedure (aka function/subroutine) at all because it already exists in the form of the language primitive procedure reverse.

The reason it works that way is pretty simple: in UCBLogo, the way one represents a "string" made up of a number of words is as a bracketed list, what in UCBLogo parlance is the list, or sentence, data type. The reverse procedure operates on lists, same as the Perl function of the same name, but the fact that the list data type in UCBLogo is in effect its string data type eliminates a middleman.

Thus, no procedure definition is needed, and using it looks like this:

reverse [  one   two three four    ]

The output looks like this:

[four three two one]

There are some definite advantages to treating all data as lists (the other type of lists in UCBLogo being known as words).

print substr("Just another Perl hacker", 0, -2);
- apotheon
CopyWrite Chad Perrin


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Re^2: Five Ways to Reverse a String of Words (C#, Perl 5, Perl 6, Ruby, Haskell)
by EdwardG (Vicar) on Dec 13, 2006 at 12:32 UTC
    And by the same token;
    C:\>perl -e "$,=' ';print reverse qw/ one two three four /;" four three two one C:\>

     

      Absolutely. You can do list-oriented programming in Perl as well. The problem that arises is that while doing list-oriented programming you lose the ability to do certain text manipulations without breaking the list-oriented style. For instance, you run afoul of problems with regular expressions over a string if you represent the string as an array. Similarly, you must convert to a list when you read strings in from external sources.

      There are many things that Perl does better for text processing than UCBLogo, but I think UCBLogo wins on this one score.

      print substr("Just another Perl hacker", 0, -2);
      - apotheon
      CopyWrite Chad Perrin

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