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|
#!perl
###############################################################################
=comment
Perl Weekly Challenge 198
=========================
TASK #2
-------
*Prime Count*
Submitted by: Mohammad S Anwar
You are given an integer $n > 0.
Write a script to print the count of primes less than $n.
Example 1
Input: $n = 10
Output: 4 as in there are 4 primes less than 10 are 2, 3, 5, 7.
Example 2
Input: $n = 15
Output: 6
Example 3
Input: $n = 1
Output: 0
Example 4
Input: $n = 25
Output: 9
=cut
###############################################################################
#--------------------------------------#
# Copyright © 2023 PerlMonk Athanasius #
#--------------------------------------#
#==============================================================================
=comment
Interface
---------
If no command-line argument is given, the test suite is run.
=cut
#==============================================================================
use strict;
use warnings;
use Const::Fast;
use ntheory qw( prime_count );
use Regexp::Common qw( number );
use Test::More;
const my $TEST_FIELDS => 3;
const my $USAGE =>
"Usage:
perl $0 [<list> ...]
perl $0
[<list> ...] An integer greater than zero\n";
#------------------------------------------------------------------------------
BEGIN
#------------------------------------------------------------------------------
{
$| = 1;
print "\nChallenge 198, Task #2: Prime Count (Perl)\n\n";
}
#==============================================================================
MAIN:
#==============================================================================
{
my $args = scalar @ARGV;
if ($args == 0)
{
run_tests();
}
elsif ($args == 1)
{
my $n = $ARGV[ 0 ];
$n =~ / ^ $RE{num}{int} $ /x
or error( qq["$_" is not a valid integer] );
$n > 0 or error( "$n is not greater than zero" );
print "Input: \$n = $n\n";
printf "Output: %d\n", count_primes( $n );
}
else
{
error( "Expected 1 or 0 command line arguments, found $args" );
}
}
#------------------------------------------------------------------------------
sub count_primes
#------------------------------------------------------------------------------
{
my ($n) = @_;
# Note: The count returned by Math::Prime::Util::prime_count( $x ) is
# *inclusive* of $x
return prime_count( $n - 1 );
}
#------------------------------------------------------------------------------
sub error
#------------------------------------------------------------------------------
{
my ($message) = @_;
die "ERROR: $message\n$USAGE";
}
#------------------------------------------------------------------------------
sub run_tests
#------------------------------------------------------------------------------
{
print "Running the test suite\n";
while (my $line = <DATA>)
{
chomp $line;
my ($test_name, $n, $expected) = split / \| /x, $line, $TEST_FIELDS;
s/ ^ \s* (.+?) \s* $ /$1/x # Trim whitespace
for $test_name, $n, $expected;
is count_primes( $n ), $expected, $test_name;
}
done_testing;
}
###############################################################################
__DATA__
Example 1| 10| 4
Example 2| 15| 6
Example 3| 1| 0
Example 4| 25| 9
Large n | 1000000| 78498
Huge n |1234567890|62106578
|
