Consider the following:
#include "share/atspre_staload.hats"
typedef oobindex(n:int) = [m:int | m >= ~1; m < n] int(m)
typedef coins(n:int) = arrayref(int, n)
fun count{n:nat}(sum: int, i: oobindex(n), coins: coins(n)): int =
ifcase
| i < 0 => 0
| sum < 0 => 0
| sum = 0 => 1
| _ => smaller + same where {
val smaller = count(sum, i-1, coins)
val same = count(sum - coins[i], i, coins)
}
val coins = (arrayref)$arrpsz{int}(1, 5, 10, 25, 50)
implement main0() =
println!("(A) count(1000) = ", count(1000, 4, coins))
and:
#include "share/atspre_staload.hats"
typedef oobindex(n:int) = [m:int | m >= ~1; m < n] int(m)
typedef coins(n:int) = arrayref(int, n)
fun count{n:nat}(sum: int)(i: oobindex(n))(coins: coins(n)): int =
ifcase
| i < 0 => 0
| sum < 0 => 0
| sum = 0 => 1
| _ => smaller + same where {
val smaller = count(sum)(i-1)(coins)
val same = count(sum - coins[i])(i)(coins)
}
val coins = (arrayref)$arrpsz{int}(1, 5, 10, 25, 50)
implement main0() =
println!("(A) count(1000) = ", count(1000)(4)(coins))
Compiled and timed:
$ patscc -DATS_MEMALLOC_GCBDW -O3 -o coin coin.dats -lgc
$ patscc -DATS_MEMALLOC_GCBDW -O3 -o coin2 coin2.dats -lgc
$ for v in '' 2; do for x in 1 2 3; do time ./coin$v; done; echo -----; done
(A) count(1000) = 801451
real 0m0.363s
user 0m0.355s
sys 0m0.009s
(A) count(1000) = 801451
real 0m0.307s
user 0m0.303s
sys 0m0.004s
(A) count(1000) = 801451
real 0m0.307s
user 0m0.305s
sys 0m0.002s
-----
(A) count(1000) = 801451
real 0m33.251s
user 0m36.228s
sys 0m7.117s
(A) count(1000) = 801451
real 0m35.519s
user 0m38.485s
sys 0m6.951s
(A) count(1000) = 801451
real 0m36.157s
user 0m39.029s
sys 0m7.151s
-----
s -lgc
"Introduction to Programming in ATS" already recommends against currying,
but with the above in mind I'd recommend against it a bit more strongly :)
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