fn subtraction(state: &mut State) {
    let a = state.stack.pop();
    let b = state.stack.pop();
    state.stack.push(b - a);
}
// subtraction performs b - a where a is popped from the stack before b
subtraction performs b - a where a is popped from the stack before b
subtraction performs b - a where a is popped from the stack before b
fn subtraction(state: &mut State) {
    let a = state.stack.pop();
    let b = state.stack.pop();
    state.stack.push(b - a);
}
fn subtraction ( state : & mut State ) { let a = state . stack . pop ( ) ; let b = state . stack . pop ( ) ; state . stack . push ( b - a ) ; }
subtraction performs b - a where a is popped from the stack before b
subtraction performs b - a where a is popped from the stack before b
state
&mut State
state
&mut State