f
true
true
x
s
y
f
isNat
x
isNat
y
s
x
double
s
y
isNat
0
true
isNat
s
x
isNat
x
double
0
0
double
s
x
s
s
double
x
2.2
isNat
s
x
isNat
x
f
true
true
x
s
y
double
s
y
f
true
true
x
s
y
isNat
y
f
true
true
x
s
y
f
isNat
x
isNat
y
s
x
double
s
y
double
s
x
double
x
f
true
true
x
s
y
isNat
x
true
f
true
true
x
s
y
f
isNat
x
isNat
y
s
x
double
s
y
true
Failed!
NaTT
certifiable-1.6