CODEWITHSUNDEEP
c++loops
kyle newton
kyle newton

Reputation: 81

Increment a counter in a constant function

I'm attempting to keep a counter of how many times a while loop is run through. However, the code was given to me, and I'm not sure which way to modify the code to be able to increment the code.

int findPos( const HashedObj & x ) const
{
    int offset = 1;
    int currentPos = myhash( x );

    while( array[ currentPos ].info != EMPTY &&
           array[ currentPos ].element != x )
    {
        currentPos += offset;  // Compute ith probe
        offset += 2;
        incrementCounter++;
        if( currentPos >= array.size( ) )
            currentPos -= array.size( );
    }

    return currentPos;
}

When I compile this, I get "incrementCounter cannot be modified because it is being accessed through a const object"

When I see this, I know that I can't edit a value in a const function, but I'm not sure how to do this.

Upvotes: 0

Views: 1071

Answers (1)

P.W
P.W

Reputation: 26800

Declare incrementCounter as mutable like this: 

mutable int  incrementCounter;

Then you will be able to change it in the findPos function.

mutable -
applies to non-static class members of non-reference non-const type and specifies that the member does not affect the externally visible state of the class (as often used for mutexes, memo caches, lazy evaluation, and access instrumentation). mutable members of const class instances are modifiable.
(Note: the C++ language grammar treats mutable as a storage-class-specifier, but it does not affect storage class.)

Upvotes: 5

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