# anagram.awk --- An implementation of the anagram finding algorithm
# from Jon Bentley's "Programming Pearls", 2nd edition.
# Addison Wesley, 2000, ISBN 0-201-65788-0.
# Column 2, Problem C, section 2.8, pp 18-20.
#
# This program requires gawk 4.0 or newer.
# Required gawk-specific features:
# - True multidimensional arrays
# - split() with "" as separator splits out individual characters
# - asort() and asorti() functions
#
# See http://savannah.gnu.org/projects/gawk.
#
# Arnold Robbins
# [email protected]
# Public Domain
# January, 2011

/'s$/ { next } # Skip possessives
{
key = word2key($1) # Build signature
data[key][$1] = $1 # Store word with signature
}
# word2key --- split word apart into letters, sort, joining back together

function word2key(word, a, i, n, result)
{
n = split(word, a, "")
asort(a)

for (i = 1; i <= n; i++)
result = result a[i]

return result
}
END {
sort = "sort"
for (key in data) {
# Sort words with same key
nwords = asorti(data[key], words)
if (nwords == 1)
continue

# And print. Minor glitch: trailing space at end of each line
for (j = 1; j <= nwords; j++)
printf("%s ", words[j]) | sort
print "" | sort
}
close(sort)
}