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[Relay] Add list update to prelude (apache#2866)
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wweic committed Mar 24, 2019
1 parent 63b9c6c commit 2cf1a8e
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20 changes: 20 additions & 0 deletions python/tvm/relay/prelude.py
Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,25 @@ def define_list_nth(self):
s_case = Clause(PatternConstructor(self.s, [PatternVar(y)]), self.nth(self.tl(x), y))
self.mod[self.nth] = Function([x, n], Match(n, [z_case, s_case]), a, [a])

def define_list_update(self):
"""Defines a function to update the nth element of a list and return the updated list.
update(l, i, v) : list[a] -> nat -> a -> list[a]
"""
self.update = GlobalVar("update")
a = TypeVar("a")
l = Var("l", self.l(a))
n = Var("n", self.nat())
v = Var("v", a)

y = Var("y")

z_case = Clause(PatternConstructor(self.z), self.cons(v, self.tl(l)))
s_case = Clause(PatternConstructor(self.s, [PatternVar(y)]),
self.cons(self.hd(l), self.update(self.tl(l), y, v)))

self.mod[self.update] = Function([l, n, v], Match(n, [z_case, s_case]), self.l(a), [a])

def define_list_map(self):
"""Defines a function for mapping a function over a list's
elements. That is, map(f, l) returns a new list where
Expand Down Expand Up @@ -470,6 +489,7 @@ def __init__(self, mod):
self.define_nat_add()
self.define_list_length()
self.define_list_nth()
self.define_list_update()
self.define_list_sum()

self.define_tree_adt()
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18 changes: 18 additions & 0 deletions tests/python/relay/test_adt.py
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@
hd = p.hd
tl = p.tl
nth = p.nth
update = p.update
length = p.length
map = p.map
foldl = p.foldl
Expand Down Expand Up @@ -148,6 +149,23 @@ def test_nth():

assert got == expected

def test_update():
expected = list(range(10))
l = nil()
# create zero initialized list
for i in range(len(expected)):
l = cons(build_nat(0), l)

# set value
for i, v in enumerate(expected):
l = update(l, build_nat(i), build_nat(v))

got = []
for i in range(len(expected)):
got.append(count(intrp.evaluate(nth(l, build_nat(i)))))

assert got == expected

def test_length():
a = relay.TypeVar("a")
assert mod[length].checked_type == relay.FuncType([l(a)], nat(), [a])
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