迭代Perl数组的最佳方法 [英] Best way to iterate through a Perl array
问题描述
哪个是迭代Perl数组的最佳实现(在速度和内存使用方面)?有没有更好的方法? ( @Array
无需保留)。
Which is the best implementation(in terms of speed and memory usage) for iterating through a Perl array? Is there any better way? (@Array
need not be retained).
foreach (@Array)
{
SubRoutine($_);
}
实施2
Implementation 2
while($Element=shift(@Array))
{
SubRoutine($Element);
}
实施3
Implementation 3
while(scalar(@Array) !=0)
{
$Element=shift(@Array);
SubRoutine($Element);
}
实施4
Implementation 4
for my $i (0 .. $#Array)
{
SubRoutine($Array[$i]);
}
实施5
Implementation 5
map { SubRoutine($_) } @Array ;
推荐答案
-
In速度方面:#1和#4,但在大多数情况下并不多。
In terms of speed: #1 and #4, but not by much in most instances.
你可以写一个基准来确认,但我怀疑你会发现#1和#4稍微快一些,因为迭代工作是在C而不是Perl完成的,并且不会发生数组元素的不必要的复制。 (
$ _
别名到#1中的元素,但#2和#3实际上复制来自的标量数组。)You could write a benchmark to confirm, but I suspect you'll find #1 and #4 to be slightly faster because the iteration work is done in C instead of Perl, and no needless copying of the array elements occurs. (
$_
is aliased to the element in #1, but #2 and #3 actually copy the scalars from the array.)#5可能类似。
就内存使用而言:他们'除了#5之外都是一样的。
In terms memory usage: They're all the same except for #5.
for(@a)
是特殊的,以避免扁平化阵列。循环遍历数组的索引。for (@a)
is special-cased to avoid flattening the array. The loop iterates over the indexes of the array.在可读性方面:#1。
在灵活性方面:#1 /#4和#5。
In terms of flexibility: #1/#4 and #5.
#2不支持错误的元素。 #2和#3具有破坏性。
#2 does not support elements that are false. #2 and #3 are destructive.
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