RosettaCodeData/Task/Four-is-magic/UNIX-Shell/four-is-magic.sh

82 lines
2.6 KiB
Bash

#!/usr/bin/env bash
name_of() {
# return the English name for a numeric value
local -i n=$1
if (( n < 0 )); then
printf 'negative %s\n' "$(name_of $(( -n )))"
return 0
fi
# Names for numbers that fit in a bash integer
local -A names=([0]=zero [1]=one [2]=two [3]=three [4]=four [5]=five
[6]=six [7]=seven [8]=eight [9]=nine [10]=ten [11]=eleven
[12]=twelve [13]=thirteen [14]=fourteen [15]=fifteen
[16]=sixteen [17]=seventeen [18]=eighteen [19]=nineteen
[20]=twenty [30]=thirty [40]=forty [50]=fifty [60]=sixty
[70]=seventy [80]=eighty [90]=ninety [100]=hundred
[1000]=thousand [1000000]=million [1000000000]=billion
[1000000000000]=trillion [1000000000000000]=quadrillion
[1000000000000000000]=quintillion)
# The powers of 10 above 10, in descending order
local powers_of_10=($(printf '%s\n' "${!names[@]}" | sort -nr | grep '00$'))
# find the largest power of 10 that is smaller than n
local -i i=0
local -i p=${powers_of_10[i]}
while (( p > n && i < ${#powers_of_10[@]}-1 )); do
i=i+1
p=${powers_of_10[$i]}
done
# if we found one, split on it and construct quotient 'name' remainder
if (( n >= p )); then
local -i quotient=n/p
local -i remainder=n%p
local remname=
if (( remainder > 0 )); then
remname=$(name_of $remainder)
fi
printf '%s %s\n' "$(name_of $quotient)" "${names[$p]}${remname:+ $remname}"
elif (( n > 20 )); then
# things are a little different under 100, since the multiples of
# 10 have their own names
local -i remainder=n%10
local -i tens=n-remainder
local remname=
if (( remainder > 0 )); then
remname=-$(name_of $remainder)
fi
printf '%s\n' "${names[$tens]}${remname:+$remname}"
else
printf '%s\n' "${names[$n]}"
fi
return 0
}
# Convert numbers into the length of their names
# Display the series of values in name form until
# the length turns into four; then terminate with "four is magic."
# Again, takes a second argument, this time a prefix, to
# facilitate tail recursion.
four_is_magic() {
local -i n=$1
local prefix=$2
local name=$(name_of $n)
# capitalize the first entry
if [[ -z $prefix ]]; then
name=${name^}
fi
# Stop at 4, otherwise count the length of the name and recurse
if (( $n == 4 )); then
printf '%s%s is magic.\n' "${prefix:+$prefix, }" "$name"
else
local -i len=${#name}
four_is_magic "$len" "${prefix:+$prefix, }$name is $(name_of $len)"
fi
}