In modern C, that could only be a macro. Example:
#define ElementFn(name) function_ ## name
#define Private
typedef float Logical;
typedef float Real;
Private Logical ElementFn(lifestyleRollupContribution)(
Real gross,
Real net
) {
return 2.0f;
}
int main(void) {
printf("%f", ElementFn(lifestyleRollupContribution)(3.05f, 42.0f));
return 0;
}