Logoical operators in return

Question

I have a function in a program that should return an int, but the return looks like this:

return wordlength > 6.0 &&  wordlength< 9.0
       && strcasestr (string, "substring1") && strcasestr (string, "substring2")
       && strcasestr (string, "substring2") && strcasestr (string, "substring4")

The wordlength is a double that contains the average length of the words in the string.

My question is what does the return statement actually return?

It returns an `int` that tells you if all those conditions are satisfied. — Poshi, Mar 19 '19 at 09:43
Welcome to SO!... It will return a boolean value. Easiest way to check is by looking at the function headline `return_type FUNCTION_NAME(arguments_list)`. — Sven-Eric Krüger, Mar 19 '19 at 09:44
A ture or false value. But the function is int so shouldn't it return int? — tocsika7, Mar 19 '19 at 09:44
On most CPUs boolean values are mapped on an integer type... 0b00000001 = "True" and 0b00000000 = "False" — Sven-Eric Krüger, Mar 19 '19 at 09:45
in C true is just 1 and false is just 0. there aren't even true/false keywords in C. to be more precise, false is 0 and true is any non zero integer. but conditions returns 1/0 — , Mar 19 '19 at 09:49

Lundin · Accepted Answer · 2019-03-19T09:51:04.367

The operator precedence rules say that relational operators like < take precedence over &&. Therefore the sub-expression wordlength > 6.0 && wordlength< 9.0 is equivalent to (wordlength > 6.0) && (wordlength< 9.0).

Once that's sorted out, note that && has left-to-right associativity. Meaning that in case there are several of the same operator with the same precedence in the same expression, like for example a && b && c, then it is equivalent to (a && b) && c.

The logical operators like && has a "short-circuit" order of evaluation. Meaning that in 0 && b, only the operand 0 is evaluated/executed. See Is short-circuiting logical operators mandated? And evaluation order?

And finally, logically expressions in C do not yield a boolean type (like in C++) but an int of value 1 or 0. Even though the type is int, this can be regarded as if it is of type bool though, and you can safely write code such as bool b = x && y;.

You example you gave would be correct with `||` instead of `&&`, or with `0` instead of `1` but in this case both operands needs to be evaluated. — , Mar 19 '19 at 09:50

Logoical operators in return

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