Ethiopian multiplication: Difference between revisions

While breaking if the --posix flag is passed to bash, the following is a slight alternative to the above that forces variable scoping and avoids the use of the *, /, and % operators.

{{works with|bash}}

<lang bash>halve() {

echo -n $(( $1 >> 1 ))

}

double() {

echo -n $(( $1 << 1 ))

}

is_even() {

[ $(( $1 & 1 )) -eq 0 ]

}

multiply() {

local plier=$1

local plicand=$2

local result=0

while [ $plier -gt 0 ]

do

! is_even $plier && (( result += plicand ))

plier=$( halve $plier )

plicand=$( double $plicand )

done

echo -n $result

}

echo $( multiply 17 34 )</lang>