CODEWITHSUNDEEP
c++
jwm
jwm

Reputation: 5030

Variable assignment in an if-condition statement

I have seen some codes that perform variable assignment in the if condition, for example:

if((data->symStem = sym.isStem())==TRUE)  //if condition
{
   // do something
}

To my understanding, in the if condition above, sym.isStem() is first assigned to data->symStem, and thereafter, the equality condition (for sym.isStem() or data->sysStem) is evaluated. Please correct me if there is something wrong.

I wonder if there is any particular reason to do so except that the codes are more compact.

Upvotes: 1

Views: 217

Answers (3)

SergeyA
SergeyA

Reputation: 62563

In C++17, this gets a certain twist - now you are not only allowed to assign variables, you are also allowed to create and initialize variables in the if condition (it is called if statement with initializer):

if (int a = foo(); a != 0) {
//...
}

That has a benefit of being able to introduce scoped variables without having to put new set of artifical braces around it, like pre-C++17 you'd have to do

{
int a = foo();
if (a != 0) {
//...
}
}

Upvotes: 1

463035818_is_not_an_ai
463035818_is_not_an_ai

Reputation: 122133

Assignment is typically implemented as

struct foo {
    foo& operator=(const foo& other) {
        // do the assignment
        return *this;
    }
};

and the reason is to allow chaining as in your example. There is really not much more to it than saving a line of code.

Upvotes: 0

Hatted Rooster
Hatted Rooster

Reputation: 36463

No, there's no reason to do it other than writing it in 1 line vs 2 lines.

Upvotes: 3

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