Four is magic: Difference between revisions

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=={{header|UNIX Shell}}==

<lang sh># ~~Names for numbers that fit in a~~ bash ~~integer~~

<lang sh>#!/usr/bin/env bash

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~~declare~~ -A names=([0]=zero [1]=one [2]=two [3]=three [4]=four [5]=five ~~[6]=six~~

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[7]=seven [8]=eight [9]=nine [10]=ten [11]=eleven ~~[12]=twelve~~

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[13]=thirteen [14]=fourteen [15]=fifteen ~~[16]=sixteen~~

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[17]=seventeen [18]=eighteen [19]=nineteen ~~[20]=twenty~~

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[30]=thirty [40]=forty [50]=fifty [60]=sixty ~~[70]=seventy~~

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[80]=eighty [90]=ninety [100]=hundred ~~[1000]=thousand~~

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[~~1000000~~]=~~million~~ [~~1000000000~~]=~~billion~~ [~~1000000000000~~]=~~trillion~~

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~~[1000000000000000]=quadrillion~~ [1000000000000000000]=quintillion)

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# The powers of 10 above 10, in descending order

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powers_of_10=($(printf '%s\n' "${!names[@]}" | sort -nr | grep '00$'))

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# ~~Function~~ to return the name of a ~~number given in~~ numeric ~~form~~

# If the second parameter is passed in, it is appended to the name

# with a space between them; this is to facilitate tail recursion

name_of() {

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# return the English name for a numeric value

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local -i n=$1

# Names for numbers that fit in a bash integer

local suffix=$2

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local -A names=([0]=zero [1]=one [2]=two [3]=three [4]=four [5]=five

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[6]=six [7]=seven [8]=eight [9]=nine [10]=ten [11]=eleven

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[12]=twelve [13]=thirteen [14]=fourteen [15]=fifteen

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[16]=sixteen [17]=seventeen [18]=eighteen [19]=nineteen

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[20]=twenty [30]=thirty [40]=forty [50]=fifty [60]=sixty

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[70]=seventy [80]=eighty [90]=ninety [100]=hundred

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[1000]=thousand [1000000]=million [1000000000]=billion

[1000000000000]=trillion [1000000000000000]=quadrillion

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[1000000000000000000]=quintillion)

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# The powers of 10 above 10, in descending order

# check for easy case first - exclude exact powers of 10

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local powers_of_10=($(printf '%s\n' "${!names[@]}" | sort -nr | grep '00$'))

# above 10 as we'll need to stick a "one" in front of those.

if [[ $n != *00 && -n ${names[$n]} ]]; then

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printf '%s%s\n' "${names[$n]}" ~~${suffix:+" $suffix"}~~

return 0

fi

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local -i n=$1

# find the largest power of 10 that is smaller than n

local -i i=0

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# if we found one, split on it and construct quotient 'name' remainder

# since both quotient and remainder require recursion, we can't use

# tail-recursion for both.

if (( n >= p )); then

local -i quotient=n/p

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remname=$(name_of $remainder)

fi

~~name_of~~ "$quotient" "${names[$p]}${remname:+ $remname~~}${suffix:+ $suffix~~}"

printf '%s %s\n' "$(name_of $quotient)" "${names[$p]}${remname:+ $remname}"

elif (( n > 20 )); then

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else

# things are a little different under 100, since the multiples of

# 10 have their own names

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remname=-$(name_of $remainder)

fi

printf '~~%s%s~~%s\n' "${names[$tens]}~~" "~~${remname~~}" ${suffix~~:+" $~~suffix~~"}

printf '%s\n' "${names[$tens]}${remname:+$remname}"

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else

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printf '%s\n' "${names[$n]}"

fi