Insane problem regarding variables in an if statement

[AMG]

Hello, im new here and i am having a problem thats driving me absolutely insane. Long story short, im programming a simple game engine and i am writing a function to procedually generate a grid by creating a vertex and an index buffer.
(im using D3D11).

	for(int i=0;i < indiceCount; i++)
	{
		c++;
		if(a==(4+c*5))
		{
			indices.push_back(a);
		}
		a++;
	}

Where c is an int. Now the problem is, that i dont want to add an indice at certain locations which is why i am checking the indice's value (a). In this line: if(a==(4+c*5)), if i replace c with a constant value, such as 5 (by removing the variable c and just putting 5 in its place), then the indice with a value of 29 is left out. Now if i were to use that c to leave all of the unneeded ones out, it wont work at all and none of them are left out. It seems as if i cannot use a changing variable in an if statement? Thats absolutely ridicilous. When i dont increment the c (c++), it leaves one indice out like it should, but as soon as i try to increment it it just doesnt leave any of the indices out. This is driving me crazy.


Thanks in advance,
AMG.

[Mats]

Is the start value of a such that (4 + c * 5) will always be a greater value than a in every loop?

[Albatross]

The expression (4+c*5) grows five times faster than a does and is larger to begin with, so a will never equal to that expression (assuming c is less than or equal to 3 at the start)

If you're looking for all indices with a value of (4+c*5) to leave out where c is a value ranging from 0 to indiceCount, then instead you may want to consider checking if a, when reduced by four and divided by 5, has no remainder.

-Albatross

[AMG]

Thanks to the both of you. The mistake was so simple yet when looking at a piece of code for a long time, one can easily miss such a trivial mistake. Thanks again! I got it fixed.