help with strcmp()

Can someone how the following line works step by step? I know what it does, but I guess I don't understand the syntax.

Code:

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return strcmp(word, "STOP") ! = 0;

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The line is supposed to return 0 if the string word = STOP, and return 1 if thats not true. I dont understand how or why though.

It returns the truth value (which in C is an int 0-false nonzero-true) of the statement strcmp(word,"STOP") != 0;

If word contains exactly "STOP" then strcmp(word,"STOP") evaluates to 0 and strcmp(word,"STOP") != 0 evaluates to false-0, so the 0 is the value returned.

If word is differet from "STOP" then strcmp(word,"STOP") returns some non-zero value and strcmp(word,"STOP") != 0 evaluates to true-nonzero, so a nonzero value is returned.

It's the same as saying this:

Code:

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int result = strcmp(word,"STOP");
return result != 0;

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I don't understand the need for the != 0 part, at all. You can use the return from strcmp() as a bool (true false) expression, just as it is, without that part being tacked on to it.

Quote:

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Originally Posted by Adak

I don't understand the need for the != 0 part, at all.

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Some people (not me) think it adds clarity to the code. Maybe it was written by a programmer of a language that doesn't convert ints to bools.

This doesn't really both me, but sometimes I see java programmers write ridiculous crap like:

Code:

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if ((a!=0)==true){

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Because strcmp() returns an integer, you must translate it to a bool value in C++ (and in C99?). Leaving type casting to compiler will be dangerous.

strcmp() returns false if strings are equal for example while you may expect it to return true in this case.

Code:

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if ((a!=0)==true){

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It is the exact code you should write if "a" is not bool, in any language the bool type is defined in it.

Quote:

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Originally Posted by Adak

I don't understand the need for the != 0 part, at all. You can use the return from strcmp() as a bool (true false) expression, just as it is, without that part being tacked on to it.

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I think that it makes sense. strcmp(a, b) == 0 tests if a and b are equal. strcmp(a, b) != 0 tests if a and b and not equal. strcmp(a, b) < 0 tests if a is less than b, etc. On the other hand, !strcmp(a, b) tests for... a is not equal to b? Oops.

Quote:

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Originally Posted by laserlight

I think that it makes sense. strcmp(a, b) == 0 tests if a and b are equal. strcmp(a, b) != 0 tests if a and b and not equal. strcmp(a, b) < 0 tests if a is less than b, etc. On the other hand, !strcmp(a, b) tests for... a is not equal to b? Oops.

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I think it's the return statement that makes things a bit confusing.

Quote:

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Originally Posted by siavoshkc

Code:

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if ((a!=0)==true){

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It is the exact code you should write if "a" is not bool, in any language the bool type is defined in it.

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No it isn't. Even if you can't implicitly convert an int to a bool, (a!=0) is a bool, so the (...==true) part is useless.

Quote:

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Originally Posted by NeonBlack

No it isn't. Even if you can't implicitly convert an int to a bool, (a!=0) is a bool, so the (...==true) part is useless.

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You know, you are right.