Re: if statement not working
22/03/2002 5:04:01 PM, David Cuny <dcuny at LANSET.COM> wrote:
>
>Euphoria isn't C, or Pascal, or any other language. That's a good thing. But
>it doesn't exist in a vaccum, either. And newbies (and myself) seem to be
>tripped up by two features in Euphoria.
>
>1. The '=' sign. I've argued against the current implementation until I was
>blue in my face. I think the current behavior is more likely to result in
>buggy code. In what other language does an '==' cause the program to come to
>a hard stop?
I can see where compare() came from. In 'C' one has to use strcmp() for a good
reason, because
strings, and arrays in general, are really pointers. So:
char *s, *t;
if (s == t) // actually checks to see if 's' and 't' are literally
addressing the same RAM
location.
but
if (strcmp(s,t) == 0) // is calling a function to examine each byte in the
character arrays
However, as David points out, Euphoria ain't 'C'. In Eu, there are no pointers.
So there can be no
confusion about '=' referring to either the address or contents of a sequence.
It has to be the
contents because you cannot reference its address.
>The only good thing about this is that it prepares you for C coding, by using
>compare() every time you deal with a string. After a while, it becomes second
>nature.
And of course, we should all be preparing to abandon Eu for C 
>But Robert sees this as a feature, and it's not going to change.
Go figure!
>2. Using slices on strings. This "gotcha" was a handmine that littered a lot
>of my early code. This initially looks like a good idea, until you get a
>string shorter than you expected. So you write:
>
> if s[1..3] = "/* "
>
>and the code goes into cardiac arrest if the length of s is less than 3. If
>nothing else, Euphoria should offer a substring function that would provide
>some safety:
>
> if substr( s, 1, 3 ) = "/* "
>
>Of course, it would have to pad the string that's returned with nulls so the
>length would match what was expected, or else *boom*.
>
>Adding short-circuiting helps, but still, I think it's a nasty trap that
>could easily turn someone away from using Euphoria.
I just tripped against this stupid restriction again last night. I've written a
function called
begins() to help me out, but it ain't pretty.
if begins(s, t) then ...
I originally wrote:
if equal(s[1..length(t)], t) then ...
but this fails whenever s is shorter than t.
(I'm writting a simple text adventure game to highlight a number of new
additions to win32lib. If
things go well, I'll have it operational by the end of the weekend.)
-------
Derek.
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