#!/usr/bin/perl
use v5.40;

sub sum( @numbers ) {
    my $sum_num = 0;
    foreach my $num (@numbers) {
        $sum_num = $sum_num + $num
    }
    return $sum_num
}

sub fold( $func, $initial, @list ) {
    my $output = $initial;
    foreach my $item (@list) {
        $output = $func->($output, $item);
    }

    return $output
}

sub mmap( $func, @list ) {
    my @output;
    foreach my $item (@list) {
        my $result = $func->($item);
        push(@output, $result);
    }

    return @output;
}

sub map2( $func, @list1, @list2 ) {
    my @output;

    my $list1_length = $#list1;
    my $list2_length = $#list2;

    my $length = $list1_length;
    if($list2_length < $length) {
        $length = $list2_length;
    }

    for(my $i = 0; $i < $length; $i++) {
        push(@output, $func->(@list1[$i], @list2[$i]));
    }

    return @output;
}

sub sum_op( $a, $b ) {
    return $a + $b
}

sub sum_op_2( $a ) {
    return $a * 2;
}

sub diff_op( $a, $b ) {
    return $a - $b;
}

my @test = (1,2,3,4,5,6,7,8,9,10);

print(fold(\&sum_op, 0, @test));

print(mmap(\&sum_op_2, @test));

print(map2(\&diff_op, @test, @test));