map mystery

[Occidental]

my @A = qw/one two three/;

print "A: ";
print join " ", @A;
print "\n";

my @A1 = map (ucfirst, @A);
print "A1: ";
print join " ", @A1;
print "\n";

my @A2 = map (reverse, @A);
print "A2: ";
print join " ", @A2;
print "\n";

my $y = reverse "one";
print "y: $y\n";
===============================================
gives:

A: one two three
A1: One Two Three
A2:
y: eno


===============================================

The first map operation works, and reverse works on a scalar, but the
array A2 is empty. Anyone know why?

 

[xhoster]

my @A = qw/one two three/;

print "A: ";
print join " ", @A;
print "\n";

my @A1 = map (ucfirst, @A);
print "A1: ";
print join " ", @A1;
print "\n";

my @A2 = map (reverse, @A);

You are reversing the empty list, which of course just gives the empty
list. The concatenation of a bunch of empty lists is still an empty list.

The reverse only operates on $_ implicitly when it is in a scalar context,
while map invokes its thingy in a list context. So put it into scalar
context explicitly:

my @A2 = map scalar reverse, @A;

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