#!/bin/bash
#
# any2dec.sh <radix> <string_representation_in_that_radix>
#
if [[ $# -lt 2 ]]
then
    echo "Usage: $0 <radix> <string_representation_in_that_radix>"
    exit
fi
if [[ $1 -lt 2 || $1 -gt 36 ]]
then
    echo "The radix is a decimal between 2 and 36"
    exit
fi
DIGITS=0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ
LEGAL_DIGITS=$(expr substr $DIGITS 1 $1)
decimal=0
l=$(expr length $2)
pos=1;
for ((pow=l-1;pow>=0;pow--))
do
	digit=$(expr substr $2 pos 1)
	digit=&(($(expr index $LEGAL_DIGITS $digit) -1))
	if [[ $digit -eq -1 ]]
	then
		echo "Authorized digits are : $LEGAL_DIGITS"; exit
	fi
	decimal=$((decimal+digit*$1**pow))
	echo "$decimal+$digit*$1**$pow"
	pos=$((pos+1))
done
echo "decimal : $decimal"
exit