Re: lcc first experience

richard@[EMAIL PROTECTED]
 (Richard Tobin) writes:
> In article
<cf0c2e4c-e25f-4ceb-a45d-5e056817552f@[EMAIL PROTECTED]
>,
> Paul Hsieh  <websnarf@[EMAIL PROTECTED]
> wrote:
>
>>C is an uncommon language in that it does not require a comparison
>>operator in its if statements
>
> Really?  Which ones do?

Paul's statement is incorrect as written, but there's a correct and
somewhat interesting statement hiding behind it.

C is somewhat unusual in the breadth of types that are acceptable as
conditions in if statements (and while statements, and other contexts
that require conditions).  In particular, an expression of any scalar
type (i.e., any arithmetic or pointer type) can be used as a
condition; the result of the expression is implicitly compared to zero
(the meaning of "zero" varies for different scalar types), so that
zero is treated as false, and any non-zero value is treated as true.

For example, in C, this is valid:

    int x = 42;
    ...
    if (x) {   /* equivalent to "if (x != 0)" */
        /* ... */
    }

By contrast, Pascal requires a condition to be of type boolean (pardon
any syntax errors; it's been a while).

    var
        x: integer;
    ...
    x := 42;
    if x <> 0 then   (* would be illegal without the "<> 0" *)
        (* ... *)

So, in many cases, a comparison operator that would be required in
some other languages is not required in C.

This feature, as far as I've seen, is peculiar to C, to languages that
inherited it from C (C++, Perl, etc.), and perhaps to languages that
got it from C's ancestors (are there any existing B/BCPL derivatives
other than C?).  Other common languages, particularly Pascal and its
derivatives, don't do this.

(Speaking only for myself, this is not among the features of C that I
particularly like.)

-- 
Keith Thompson (The_Other_Keith) <kst-u@[EMAIL PROTECTED]
>
Nokia
"We must do something.  This is something.  Therefore, we must do this."
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