Path: utzoo!attcan!uunet!wuarchive!udel!haven!adm!news
From: CDCKAB%EMUVM1.BITNET@cunyvm.cuny.edu ( Karl Brendel)
Newsgroups: comp.lang.pascal
Subject: (R)Comparing strings...
Message-ID: <24773@adm.BRL.MIL>
Date: 15 Oct 90 13:35:41 GMT
Sender: news@adm.BRL.MIL
Lines: 47


In article <2203.27170055@cc.nu.oz.au>, v8902058@cc.nu.oz.au "Bernard"
 wrote:

>I'm sorry if this is a trival task, but I would like a function that
>compares two strings.  I would like to be able to find if a string is
>equal to, less than, or greater than another string.  I tried writing a
>routinue myself, but I just can't seem to do it, so I thought I'd ask.

What variety of Pascal are you using? Turbo Pascal can apply equality
tests directly to string types. I would expect other Pascals which offer
strings to be able to do the same thing, but that may not be the case.

A Turbo Pascal function to compare two strings could look like this:

type
  ComparisonType = (ctLessThan,ctEqual,ctGreaterThan);

function StrCompare(s1,s2 : string) : ComparisonType;
begin
  if s1 < s2 then StrCompare := ctLessThan
  else if s1 = s2 then StrCompare := ctEqual
  else StrCompare := ctGreaterThan;
end;

An example call to StrCompare:

...
  if StrCompare(LastName,Names[i]) = ctLessThan
    then Swap(LastName,Names[i]);
...

If you want a case-insensitive comparison, just make each string
uppercase before applying the tests.

Note:  passing the strings by reference rather than by value is
generally faster and reduces stack usage, but don't do that for the
case-insensitive comparison, or you'll upper-case the original strings.

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| Karl Brendel                                Centers for Disease Control |
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