Variable "g" causes error

When I replace in the Workshop1 Script the variable "c" with a "g", I get a "Wrong type..." error. Is this by design?

function main()
{
var a = 1;
var b = 2;
var g;
g = a + b;
printf("Result = %.f",g);
}

Yes, it is. That error is caused by using a variable that is already in use. They all can be found in variables.h - and "g" is the most important one.