app
app
map
f
nil
nil
app
app
map
f
app
app
cons
x
xs
app
app
cons
app
f
x
app
app
map
f
xs
app
app
append
xs
nil
xs
app
app
append
nil
ys
ys
app
app
append
app
app
cons
x
xs
ys
app
app
cons
x
app
app
append
xs
ys
app
app
zip
nil
yss
yss
app
app
zip
xss
nil
xss
app
app
zip
app
app
cons
xs
xss
app
app
cons
ys
yss
app
app
cons
app
app
append
xs
ys
app
app
zip
xss
yss
app
app
combine
xs
nil
xs
app
app
combine
xs
app
app
cons
ys
yss
app
app
combine
app
app
zip
xs
ys
yss
app
levels
app
app
node
x
xs
app
app
cons
app
app
cons
x
nil
app
app
combine
nil
app
app
map
levels
xs
app
2
map
0
nil
0
cons
0
append
0
zip
0
combine
0
levels
0
node
0
FULL
./TRS/higher-order/Bird/TreeLevels.trs