P21 - Insert an element at a given position into an array.
AUTHOR
Scott Penrose
Specification
P21 (*) Insert an element at a given position into an array.
You may choose to mutate the array in-place or to create a new
sequence and return it.
Examples
Example 1 (mutating in-place);
> my @l = <a b c d>
> insert_at('alfa',@l,2);
> say ~@l;
a alfa b c d
Example 2 (creating a copy):
> say ~insert_at_copy('alfa', <a b c d>, 2);
a alfa b c d
use v6;
# a. Simple version, in place
# @array - your "@array" must always use "@" - even for a single element
# .splice - Your array is also an object, you can call the method .splice
# - offset - where to add (starting 0)
# - length - how many to replace (0 for insert)
# - What to add
my @array = <a b c d>;
@array.splice(1, 0, 'alfa');
say ~@array;
# b. Using a sub in-place
# $in, @arr, $pos - you can insert an array in the middle of your parameters
# The array is like a reference, so if you splice on the actual array, not a
# copy of it, you will mutate the caller's copy.
# However if you modify the argument, you must declare it with "is rw" or
# the compiler may complain at you.
sub insert_at ($in, @arr, $pos) {
@arr.splice($pos - 1, 0, $in);
return;
}
my @array2 = <a b c d>;
insert_at('alfa', @array2, 2);
say ~@array2;
# c. Using a sub, returning a copy
# This time we must copy the sequence and mutate that
sub insert_at_copy($in, @list is copy, $pos) {
@list.splice($pos-1, 0, $in);
return @list;
}
say ~insert_at_copy('alfa', <a b c d>, 2);
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