CODEWITHSUNDEEP
coperatorsequality
Nikola Antonijevic
Nikola Antonijevic

Reputation: 1

Are these two expressions in C equal?

Is a*=b; the same as a*a=b;, and if not, what is its equal?

I'm little confused because I keep getting wrong answer on this test:

    #include<stdio.h>
    main () 
    {   
        int i, j, a=1, b=3; 
        for(j=1; j<3; j++)  
          a*=b;
        b++;
        printf("a=%d", a);
    }

Upvotes: 0

Views: 90

Answers (5)

Ulrick
Ulrick

Reputation: 33

First) You need to in-close the for loop with {} 

int j;
for(j=1; j<3; j++){
    printf("like this");
}

Second) a*=b is the same as a=a*b. a*a=b is trying to store the value of b in a variable called a*a.

int a*a;
int b;
a*a=b;

Which won't work because a*a isn't a valid variable name.

Lastly) The result of your code, how you have it written (once you fix the for loop with {}) should be:

a=3a=12

Upvotes: 0

alk
alk

Reputation: 70893

a *= b;

compiles.

a * a = b;

does not compile, giving something like this:

 error: lvalue required as left operand of assignment

From the above we can conclude:

No, the both expressions are not equal

As the second expression above does not compile you either have no equivalent or endlessly.

For the first expression there are (at least) two equivalents:

a = a * b;

or

a = b * a

Upvotes: 0

Jens
Jens

Reputation: 9130

What is the "wrong" answer you're getting, and which one do you expect? Note that b++ is outside of the loop; use { and } to create a block for the loop's body if you want it executed within the loop

for(j=1; j<3; j++) {
    a*=b;
    b++;
}

Other than that, to answer your actual question: What Eoin said, and in this context take a look at what an lvalue and rvalue is.

Upvotes: 1

Eoin
Eoin

Reputation: 833

a *= b; is equivalent to a = a * b;.

*= is a compound assignment operator - you can read more about them here: http://tigcc.ticalc.org/doc/opers.html#assign

There's also a good explanation of this and other operators here: http://www.tutorialspoint.com/ansi_c/c_operator_types.htm

Upvotes: 2

DeepSpace
DeepSpace

Reputation: 81594

a*=b is equivalent to a = a*b.

Upvotes: 0

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