f
true
xs
f
eq
s
length
xs
length
cons
a
xs
cons
a
xs
length
nil
0
length
cons
x
xs
s
length
xs
eq
0
0
true
eq
s
x
0
false
eq
0
s
y
false
eq
s
x
s
y
eq
x
y
2.2
length
cons
x
xs
length
xs
f
true
xs
length
cons
a
xs
f
true
xs
length
xs
f
true
xs
f
eq
s
length
xs
length
cons
a
xs
cons
a
xs
eq
s
x
s
y
eq
x
y
f
true
xs
eq
s
length
xs
length
cons
a
xs
true
f
true
xs
f
eq
s
length
xs
length
cons
a
xs
cons
a
xs
true
Failed!
NaTT
certifiable-1.6