Free and bound variables 入x.X+ Bound variable can be renamed(placeholder 入x(x+y) is same function asλz.、(z+y)c- equivalence (X+y is the scope of the binding nx int add(int x)i int add(int z) return x+ y; return Z+y x=0; //out of scopeFree and bound variables • x. x + y • Bound variable can be renamed (“placeholder”) • x. (x+y) is same function as z. (z+y) • (x+y) is the scope of the binding x int add(int x) { return x + y; } int add(int z) { return z + y; } x = 0; // out of scope! -equivalence