Perl6中是否有'clamp'或等效的方法或子程序?
例如:
my $range= (1.0 .. 9.9)
my $val=15.3;
my $clamped=$range.clamp($val);
# $clamped would be 9.9
$val= -1.3;
$clamped=$range.clamp($val);
# $clamped would be 1.0
你可能想要尝试另一种方法,即使用代理,它允许你在从容器中获取或存储值时定义“钩子”
sub limited-num(Range $range) is rw {
my ($min, $max) = $range.minmax;
my Numeric $store = $min;
Proxy.new(
FETCH => method () { $store },
STORE => method ($new) {
$store = max($min, min($max, $new));
}
)
}
# Note the use of binding operator `:=`
my $ln := limited-num(1.0 .. 9.9);
say $ln; # OUTPUT: 1
$ln += 4.2;
say $ln; # OUTPUT: 5.2
$ln += 100;
say $ln; # OUTPUT: 9.9
$ln -= 50;
say $ln; # OUTPUT: 1
$ln = 0;
say $ln; # OUTPUT: 1
这个 limited-num
会以它的最小值作为初始值,但你也可以在声明时设置它。
my $ln1 := limited-num(1.0 .. 9.9) = 5.5;
say $ln1; # OUTPUT 5.5;
my $ln2 := limited-num(1.0 .. 9.9) = 1000;
say $ln2; # OUTPUT 9.9
multi clamp ($range, $value) {
given $range {
return .max when (($value cmp .max) === More);
return .min when (($value cmp .min) === Less);
}
return $value
}
my $range = (1.0 .. 9.9);
say $range.&clamp: 15.3; # 9.9
say $range.&clamp: -1.3; # 1
my $range = 'b'..'y';
say $range.&clamp: 'a'; # b
say $range.&clamp: 'z'; # y
MOP(元对象协议)可直接探索您的P6系统中可用的对象。一个特别方便的元方法是.^methods
,适用于大多数内置对象:
say Range.^methods; # (new excludes-min excludes-max infinite is-int ...
Range
类中定义的方法,而不包括它继承的方法。(要获取所有方法,可以使用say Range.^methods: :all
。这将得到一个更大的列表。)Method+{is-nodal}.new
。因此,也许最好使用以下代码:say Range.^methods.grep: * !~~ / 'is-nodal' /;
这实现了以下目标:
(new excludes-min excludes-max infinite is-int elems iterator
flat reverse first bounds int-bounds fmt ASSIGN-POS roll pick
Capture push append unshift prepend shift pop sum rand in-range
hyper lazy-if lazy item race of is-lazy WHICH Str ACCEPTS perl
Numeric min max BUILDALL)
.^methods
提醒自己。
Range
页面。这给了我以下结果:ACCEPTS min excludes-min max excludes-max bounds
infinite is-int int-bounds minmax elems list flat
pick roll sum reverse Capture rand
say
<ACCEPTS ASSIGN-POS BUILDALL Capture Numeric Str WHICH append
bounds elems excludes-max excludes-min first flat fmt hyper
in-range infinite int-bounds is-int is-lazy item iterator
lazy lazy-if max min new of perl pick pop prepend push
race rand reverse roll shift sum unshift>.Bag
∩
<ACCEPTS Capture bounds elems excludes-max excludes-min flat
infinite int-bounds is-int list max min minmax pick
rand reverse roll sum>.Bag
显示:
Bag(ACCEPTS, Capture, bounds, elems, excludes-max, excludes-min,
flat, infinite, int-bounds, is-int, max, min, pick,
rand, reverse, roll, sum)
对于某些原因,list
,minmax
和sum
被记录为Range
方法,但它们在我的.^methods
调用中未列出。可能它们被称为Method+{is-nodal}.new
。嗯。
say Range.^lookup('minmax'); # Method+{is-nodal}.new
say Range.^lookup('minmax').name; # minmax
是的。嗯。那么我可以这样写:
say Range.^methods>>.name.sort;
(ACCEPTS ASSIGN-POS AT-POS BUILDALL Bag BagHash Capture EXISTS-POS
Mix MixHash Numeric Set SetHash Str WHICH append bounds elems
excludes-max excludes-min first flat fmt hyper in-range infinite
int-bounds is-int is-lazy item iterator lazy lazy-if list max min
minmax new of perl pick pop prepend push race rand reverse roll
shift sum unshift)
$rate= $rate > 0.1??0.1!!$rate; $rate= $rate < -0.1??-0.1!!$rate;
- drclawsay WHAT 42
之类的内容时正在使用它。我想起来唯一使用它超出此范畴的事情(还有像HOW
这样的)就是.^methods
和.^lookup
。 - raiphaugment
。诚然,它会创建全局变化,但这可能不是问题。augment class Range {
method clamp ($value) { ... }
}
编程相关内容,您需要在augment
之前在同一作用域中使用use MONKEY-TYPING
。但是这样,您可以简单地说$range.clamp(5)
。这比raiph的答案节省了一个字符,但代价是破坏了预编译(不可忽略的成本)。
my ($i,$l,$ll)=(50,1,10); say $i>$l??$l!!$i <$ll??$ll!!$i;
- drclaw