Nrthugu

I am writing a script that takes 2 numbers as an input and uses recursion to power on number to the power of the other, simple exponentiation. However I am new to scripting and cannot figure out where my syntax is errored here.

Here is the script

#!/bin/bash

echo "Enter number: "

read number

echo "Enter power: "

read power



echo "Powering $number to power of $power!" 



exp () {



    if [ $2 = 1 ]

    then

        return $1

    fi



    return $1 * $(exp $1 $2-1 )



}



result=$(exp $number, $power)



echo "Result: $result"

Currently, it kind of freezes, im not sure if I use the parameters correctly (in terms of syntax).

You need $(( )) to force arithmetic evaluation. Then you can do it with return values:

number=2 power=7

exp () {

    if [ $2 -eq 1 ]; then return $1; fi

    exp $1 $(($2-1))

    return $(($1 * $?))

}

exp $number $power; result=$?

echo "Result: $result"

but it's a bad idea, because shells kind of reserve nonzero return values to communicate failure (e.g. the above solution
will "break" set -e).

More idiomatically, you can use stdout:

set -e

number=2 power=7

exp () {

    if [ $2 -eq 1 ]; then echo $1; return; fi

    echo $(($1 * $(exp $1 $(($2-1)) ) ))

}

result=$(exp $number $power)

echo "Result: $result"

but that's kind of inefficient with all the subshells.
Best to avoid the recursion and simply loop:

number=2 power=7

exp () {

    local res=1 i=0;

    while [ $i -lt $2 ]; do res=$((res*$1)); i=$((i+1)); done

    echo $res

}

exp $number $power