我正在尝试使用动态编程计算二项式系数。我不断收到此错误
fun binomial(m:int, n:int, DP) =
if n = m orelse n = 0 then
Array2.update(DP, m, n, 1)
else if Array2.sub(DP, m, n) = ~1 then (
if Array2.sub(DP, m-1, n) = ~1 then
Array2.update(DP, m-1, n, binomial(m-1, n, DP))
else
Array2.update(DP, m-1, n, Array2.sub(DP, m-1, n));
if Array2.sub(DP, m-1, n-1) = ~1 then
Array2.update(DP, m-1, n-1, binomial(m-1, n-1, DP))
else
Array2.update(DP, m-1, n-1, Array2.sub(DP, m-1, n-1));
let
val k = Array2.sub(DP, m-1, n) + Array2.sub(DP, m-1, n-1);
in
Array2.update(DP, m, n, k)
end
)
else
Array2.update(DP, m, n, Array2.sub(DP, m, n));
Array2.sub(DP, m, n)
我不明白这个错误想说什么。
6.5-25.48 Error: right-hand-side of clause doesn't agree with function result type [literal]
expression: unit
result type: int
in declaration:
binomial =
(fn (<pat> : int,<pat> : int,DP) =>
if <exp> orelse <exp>
then Array2.update <exp>
else if <exp> then <exp> else <exp>)
谁能帮我?