#WHILE
#MAXREG 5
#IMPORT AddSub

def Prod
out: o0
in: i0, i1
aux: a0
do
    o0 := 0;
    loop i1 do 
        a0 := Add(o0,i0)();
        o0 := a0
    end
enddef

def Exp
out: o0
in: i0, i1
aux: a0, a1
do
    o0 := succ(0);
    loop i1 do 
        a0 := Prod(o0,i0)(a1);
    o0 := a0
    end
enddef

def AbsSub
out: o0
in: i0, i1
aux: a0
do
    o0 := 0;
    a0 := Sub(i0,i1)();
    o0 := IfLet(a0,a0)();   
    a0 := Sub(i1,i0)();
    o0 := IfLet(a0,a0)()    
enddef


//x0 := Exp(x1,x2)(x3,x4)
x0 := AbsSub(x1,x2)(x3)