切割是一种非常有用的组合器,可最大程度地减少代码重复。假设我想对丰富,完美,不足的数字进行分类:
USING: arrays assocs combinators formatting io kernel math
math.order math.primes.factors math.ranges sequences ;
IN: adp
CONSTANT: ADP { "deficient" "perfect" "abundant" }
: proper-divisors ( n -- seq )
dup zero? [ drop { } ] [ divisors dup length 1 - head ] if ;
: adp-classify ( n -- a/d/p )
dup proper-divisors sum <=>
{ +lt+ +eq+ +gt+ } ADP zip
H{ } assoc-clone-like at ;
: range>adp-classes ( n -- seq )
1 swap 1 <range> [ adp-classify ] map
ADP dup
[
[
[ = ] curry
[ count ] curry
] map
cleave 3array
] dip
swap zip H{ } assoc-clone-like ;
: print-adp-stats ( seq -- )
ADP [
[ dup [ swap at ] dip swap "%s: %s" sprintf ] curry
] map cleave
[ print ] tri@ ;
range>adp-classes
不编译,因为"不能将切割应用于运行时计算的值"。
如果我不能使用裂解,那么我必须从本质上做:
[ [ [ "deficient" = ] count ]
[ [ "abundant" = ] count ]
[ [ "perfect" = ] count ]
tri
] dip
la脚更长,如果钥匙串长期更长,并且会变得非常丑陋。另外,重要的是,如果在运行时生成密钥数组,则不可能在没有切割的情况下进行操作。
对于print-adp-stats
类似:如果没有cleave
,我必须在我的来源中躺在我的来源:
{
[ "deficient" dup [ swap at ] dip swap "%s: %s" sprintf ]
[ "perfect" dup [ swap at ] dip swap "%s: %s" sprintf ]
[ "abundant" dup [ swap at ] dip swap "%s: %s" sprintf ]
}
Gross。
是否有组合替换运行时计算值的cleave
?我可以在运行时允许计算时最大程度地减少丑陋的重复吗?
cleave
可能不是正确的答案。当因子说无法将某些内容应用于运行时计算的值时,这意味着可以更好地写出一些东西。我想在这里您想用直方图替换cleave
:
IN: scratchpad 100 [ { "abundant" "deficient" "perfect" } random ] replicate
histogram
--- Data stack:
H{ { "deficient" 33 } { "perfect" 30 } { "abundant" 37 } }