# File:	stringGenAlphabet.pl
# Title: 	Sorts a generated a random string of length N (ask for N)
#		over an alphabet, asks for Alphabet
# Author:	Mihaela Malita
#		Generates a random string over an alphabet
#		Input Alphabet?  ACGT	
#	 	Length of the string(integer)? 10
#		Generated string is AGTACCCCAA

print "Generates a random string over an alphabet"; 
print "Input Alphabet (ex. type ACGT)? "; 
$a = <STDIN> ;	chop($a);
@Alphabet = split('',$a); 		#transforms string in array
print "Length of your string(integer)? ";
$n = <STDIN>; chop($n);
$s = randstring($n);	#invokes subroutine
print "\nGenerated string is $s"; 
exit;
##### Subroutine: given length of string makes a random string over the alphabet
sub randstring {
	my($n) = @_;                # length of the string result
	my($s) = '';				# initialize final S with empty ''
	$len = @Alphabet;				# L is a scalar takes value = length of the array
	for ( $i = 0 ; $i < $n ; $i++) {
		$pos = int rand($len);		# generates random position in alphabet 0 < $pos < L
		$s = $s . $alphabet[$pos];	# string concatenation with .
	}	
	return $s;
}