2022-02-16 19:09:07 +00:00
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#!/bin/sh
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# $1 * $2
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# count the total decimal places
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countd() {
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m="$1"; n=${2:-0}; while [ "$m" ]; do
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: $((n+=1))
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next="${m%?}"
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[ "${m#$next}" = "." ] && {
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break
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} || {
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m="$next"
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}
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done
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echo "$n"
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}
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dn=$(countd "$2" $(countd "$1")); [ "$dn" -gt 0 ] && : $((dn-=2)) # decimal count
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# remove all decimal places
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set -- "${1%.*}${1#*.}" "${2%.*}${2#*.}"
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m="$2"; n=0; while [ "$m" ]; do
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next="${m%?}" # current is ${m#$next}
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z=""; zn=0; until [ "$zn" -eq "$n" ]; do
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z="${z}0"
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: $((zn+=1))
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done
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o="$((o+$((${m#$next}*$1))$z))"
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m="$next"
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: $((n+=1))
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done # long multiplication
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# add back decimal point using $dn
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n=0; m="$o"; [ "$dn" -gt 0 ] && while [ "$m" ]; do
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next="${m%?}"
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: $((n+=1))
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[ "$n" -eq "$dn" ] && o="$next.${o#${m%?}}"
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m="$next"
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done
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echo "$o"
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