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Lingua::EN::Inflect(3pm) User Contributed Perl Documentation Lingua::EN::Inflect(3pm)
NAME
Lingua::EN::Inflect - Convert singular to plural. Select "a" or "an".
VERSION
This document describes version 1.86 of Lingua::EN::Inflect, released October 20, 2000.
SYNOPSIS
use Lingua::EN::Inflect qw ( PL PL_N PL_V PL_ADJ NO NUM
PL_eq PL_N_eq PL_V_eq PL_ADJ_eq
A AN
PART_PRES
ORD NUMWORDS
inflect classical
def_noun def_verb def_adj def_a def_an );
# UNCONDITIONALLY FORM THE PLURAL
print "The plural of ", $word, " is ", PL($word), "\n";
# CONDITIONALLY FORM THE PLURAL
print "I saw $cat_count ", PL("cat",$cat_count), "\n";
# FORM PLURALS FOR SPECIFIC PARTS OF SPEECH
print PL_N("I",$N1), PL_V("saw",$N1),
PL_ADJ("my",$N2), PL_N("saw",$N2), "\n";
# DEAL WITH "0/1/N" -> "no/1/N" TRANSLATION:
print "There ", PL_V("was",$errors), NO(" error",$errors), "\n";
# USE DEFAULT COUNTS:
print NUM($N1,""), PL("I"), PL_V(" saw"), NUM($N2), PL_N(" saw");
print "There ", NUM($errors,''), PL_V("was"), NO(" error"), "\n";
# COMPARE TWO WORDS "NUMBER-INSENSITIVELY":
print "same\n" if PL_eq($word1, $word2);
print "same noun\n" if PL_eq_N($word1, $word2);
print "same verb\n" if PL_eq_V($word1, $word2);
print "same adj.\n" if PL_eq_ADJ($word1, $word2);
# ADD CORRECT "a" OR "an" FOR A GIVEN WORD:
print "Did you want ", A($thing), " or ", AN($idea), "\n";
# CONVERT NUMERALS INTO ORDINALS (i.e. 1->1st, 2->2nd, 3->3rd, etc.)
print "It was", ORD($position), " from the left\n";
# CONVERT NUMERALS TO WORDS (i.e. 1->"one", 101->"one hundred and one", etc.)
# IN A SCALAR CONTEXT: GET BACK A SINGLE STRING...
$words = NUMWORDS(1234); # "one thousand, two hundred and thirty-four"
$words = NUMWORDS(ORD(1234)); # "one thousand, two hundred and thirty-fourth"
# IN A LIST CONTEXT: GET BACK A LIST OF STRINGSi, ONE FOR EACH "CHUNK"...
@words = NUMWORDS(1234); # ("one thousand","two hundred and thirty-four")
# OPTIONAL PARAMETERS CHANGE TRANSLATION:
$words = NUMWORDS(12345, group=>1);
# "one, two, three, four, five"
$words = NUMWORDS(12345, group=>2);
# "twelve, thirty-four, five"
$words = NUMWORDS(12345, group=>3);
# "one twenty-three, forty-five"
$words = NUMWORDS(1234, 'and'=>'');
# "one thousand, two hundred thirty-four"
$words = NUMWORDS(1234, 'and'=>', plus');
# "one thousand, two hundred, plus thirty-four"
$words = NUMWORDS(555_1202, group=>1, zero=>'oh');
# "five, five, five, one, two, oh, two"
$words = NUMWORDS(555_1202, group=>1, one=>'unity');
# "five, five, five, unity, two, oh, two"
$words = NUMWORDS(123.456, group=>1, decimal=>'mark');
# "one two three mark four five six"
# REQUIRE "CLASSICAL" PLURALS (EG: "focus"->"foci", "cherub"->"cherubim")
classical; # USE ALL CLASSICAL PLURALS
classical 1; # USE ALL CLASSICAL PLURALS
classical 0; # USE ALL MODERN PLURALS (DEFAULT)
classical 'zero'; # "no error" INSTEAD OF "no errors"
classical zero=>1; # "no error" INSTEAD OF "no errors"
classical zero=>0; # "no errors" INSTEAD OF "no error"
classical 'herd'; # "2 buffalo" INSTEAD OF "2 buffalos"
classical herd=>1; # "2 buffalo" INSTEAD OF "2 buffalos"
classical herd=>0; # "2 buffalos" INSTEAD OF "2 buffalo"
classical 'persons'; # "2 chairpersons" INSTEAD OF "2 chairpeople"
classical persons=>1; # "2 chairpersons" INSTEAD OF "2 chairpeople"
classical persons=>0; # "2 chairpeople" INSTEAD OF "2 chairpersons"
classical 'ancient'; # "2 formulae" INSTEAD OF "2 formulas"
classical ancient=>1; # "2 formulae" INSTEAD OF "2 formulas"
classical ancient=>0; # "2 formulas" INSTEAD OF "2 formulae"
# INTERPOLATE "PL()", "PL_N()", "PL_V()", "PL_ADJ()", A()", "AN()"
# "NUM()" AND "ORD()" WITHIN STRINGS:
print inflect("The plural of $word is PL($word)\n");
print inflect("I saw $cat_count PL("cat",$cat_count)\n");
print inflect("PL(I,$N1) PL_V(saw,$N1) PL(a,$N2) PL_N(saw,$N2)");
print inflect("NUM($N1,)PL(I) PL_V(saw) NUM($N2,)PL(a) PL_N(saw)");
print inflect("I saw NUM($cat_count) PL("cat")\nNUM()");
print inflect("There PL_V(was,$errors) NO(error,$errors)\n");
print inflect("There NUM($errors,) PL_V(was) NO(error)\n";
print inflect("Did you want A($thing) or AN($idea)\n");
print inflect("It was ORD($position) from the left\n");
# ADD USER-DEFINED INFLECTIONS (OVERRIDING INBUILT RULES):
def_noun "VAX" => "VAXen"; # SINGULAR => PLURAL
def_verb "will" => "shall", # 1ST PERSON SINGULAR => PLURAL
"will" => "will", # 2ND PERSON SINGULAR => PLURAL
"will" => "will", # 3RD PERSON SINGULAR => PLURAL
def_adj "hir" => "their", # SINGULAR => PLURAL
def_a "h" # "AY HALWAYS SEZ 'HAITCH'!"
def_an "horrendous.*" # "AN HORRENDOUS AFFECTATION"
DESCRIPTION
The exportable subroutines of Lingua::EN::Inflect provide plural inflections, "a"/"an"
selection for English words, and manipulation of numbers as words
Plural forms of all nouns, most verbs, and some adjectives are provided. Where appropri-
ate, "classical" variants (for example: "brother" -> "brethren", "dogma" -> "dogmata",
etc.) are also provided.
Pronunciation-based "a"/"an" selection is provided for all English words, and most ini-
tialisms.
It is also possible to inflect numerals (1,2,3) to ordinals (1st, 2nd, 3rd) and to english
words ("one", "two", "three).
In generating these inflections, Lingua::EN::Inflect follows the Oxford English Dictionary
and the guidelines in Fowler's Modern English Usage, preferring the former where the two
disagree.
The module is built around standard British spelling, but is designed to cope with common
American variants as well. Slang, jargon, and other English dialects are not explicitly
catered for.
Where two or more inflected forms exist for a single word (typically a "classical" form
and a "modern" form), Lingua::EN::Inflect prefers the more common form (typically the
"modern" one), unless "classical" processing has been specified (see "MODERN VS CLASSICAL
INFLECTIONS").
FORMING PLURALS
Inflecting Plurals
All of the "PL_..." plural inflection subroutines take the word to be inflected as their
first argument and return the corresponding inflection. Note that all such subroutines
expect the singular form of the word. The results of passing a plural form are undefined
(and unlikely to be correct).
The "PL_..." subroutines also take an optional second argument, which indicates the gram-
matical "number" of the word (or of another word with which the word being inflected must
agree). If the "number" argument is supplied and is not 1 (or "one" or "a", or some other
adjective that implies the singular), the plural form of the word is returned. If the
"number" argument does indicate singularity, the (uninflected) word itself is returned. If
the number argument is omitted, the plural form is returned unconditionally.
The various subroutines are:
"PL_N($;$)"
The exportable subroutine "PL_N()" takes a singular English noun or pronoun and
returns its plural. Pronouns in the nominative ("I" -> "we") and accusative ("me"
-> "us") cases are handled, as are possessive pronouns ("mine" -> "ours").
"PL_V($;$)"
The exportable subroutine "PL_V()" takes the singular form of a conjugated verb
(that is, one which is already in the correct "person" and "mood") and returns the
corresponding plural conjugation.
"PL_ADJ($;$)"
The exportable subroutine "PL_ADJ()" takes the singular form of certain types of
adjectives and returns the corresponding plural form. Adjectives that are
correctly handled include: "numerical" adjectives ("a" -> "some"), demonstrative
adjectives ("this" -> "these", "that" -> "those"), and possessives ("my" -> "our",
"cat's" -> "cats'", "child's" -> "childrens'", etc.)
"PL($;$)"
The exportable subroutine "PL()" takes a singular English noun, pronoun, verb, or
adjective and returns its plural form. Where a word has more than one inflection
depending on its part of speech (for example, the noun "thought" inflects to
"thoughts", the verb "thought" to "thought"), the (singular) noun sense is pre-
ferred to the (singular) verb sense.
Hence "PL("knife")" will return "knives" ("knife" having been treated as a singu-
lar noun), whereas "PL("knifes")" will return "knife" ("knifes" having been
treated as a 3rd person singular verb).
The inherent ambiguity of such cases suggests that, where the part of speech is
known, "PL_N", "PL_V", and "PL_ADJ" should be used in preference to "PL".
Note that all these subroutines ignore any whitespace surrounding the word being
inflected, but preserve that whitespace when the result is returned. For example,
"PL(" cat ")" returns " cats ".
Numbered plurals
The "PL_..." subroutines return only the inflected word, not the count that was used to
inflect it. Thus, in order to produce "I saw 3 ducks", it is necessary to use:
print "I saw $N ", PL_N($animal,$N), "\n";
Since the usual purpose of producing a plural is to make it agree with a preceding count,
Lingua::EN::Inflect provides an exportable subroutine ("NO($;$)") which, given a word and
a(n optional) count, returns the count followed by the correctly inflected word. Hence the
previous example can be rewritten:
print "I saw ", NO($animal,$N), "\n";
In addition, if the count is zero (or some other term which implies zero, such as "zero",
"nil", etc.) the count is replaced by the word "no". Hence, if $N had the value zero, the
previous example would print the somewhat more elegant:
I saw no animals
rather than:
I saw 0 animals
Note that the name of the subroutine is a pun: the subroutine returns either a number (a
No.) or a "no", in front of the inflected word.
Reducing the number of counts required
In some contexts, the need to supply an explicit count to the various "PL_..." subroutines
makes for tiresome repetition. For example:
print PL_ADJ("This",$errors), PL_N(" error",$errors),
PL_V(" was",$errors), " fatal.\n";
Lingua::EN::Inflect therefore provides an exportable subroutine ("NUM($;$)") which may be
used to set a persistent "default number" value. If such a value is set, it is subse-
quently used whenever an optional second "number" argument is omitted. The default value
thus set can subsequently be removed by calling "NUM()" with no arguments. Hence we could
rewrite the previous example:
NUM($errors);
print PL_ADJ("This"), PL_N(" error"), PL_V(" was"), "fatal.\n";
NUM();
Normally, "NUM()" returns its first argument, so that it may also be "inlined" in contexts
like:
print NUM($errors), PL_N(" error"), PL_V(" was"), " detected.\n"
print PL_ADJ("This"), PL_N(" error"), PL_V(" was"), "fatal.\n"
if $severity > 1;
However, in certain contexts (see "INTERPOLATING INFLECTIONS IN STRINGS") it is preferable
that "NUM()" return an empty string. Hence "NUM()" provides an optional second argument.
If that argument is supplied (that is, if it is defined) and evaluates to false, "NUM"
returns an empty string instead of its first argument. For example:
print NUM($errors,0), NO("error"), PL_V(" was"), " detected.\n";
print PL_ADJ("This"), PL_N(" error"), PL_V(" was"), "fatal.\n"
if $severity > 1;
Number-insensitive equality
Lingua::EN::Inflect also provides a solution to the problem of comparing words of differ-
ing plurality through the exportable subroutines "PL_eq($$)", "PL_N_eq($$)",
"PL_V_eq($$)", and "PL_ADJ_eq($$)". Each of these subroutines takes two strings, and
compares them using the corresponding plural-inflection subroutine ("PL()", "PL_N()",
"PL_V()", and "PL_ADJ()" respectively).
The comparison returns true if:
o the strings are "eq"-equal, or
o one string is "eq"-equal to a plural form of the other, or
o the strings are two different plural forms of the one word.
Hence all of the following return true:
PL_eq("index","index") # RETURNS "eq"
PL_eq("index","indexes") # RETURNS "s:p"
PL_eq("index","indices") # RETURNS "s:p"
PL_eq("indexes","index") # RETURNS "p:s"
PL_eq("indices","index") # RETURNS "p:s"
PL_eq("indices","indexes") # RETURNS "p:p"
PL_eq("indexes","indices") # RETURNS "p:p"
PL_eq("indices","indices") # RETURNS "eq"
As indicated by the comments in the previous example, the actual value returned by the
various "PL_eq_..." subroutines encodes which of the three equality rules succeeded: "eq"
is returned if the strings were identical, "s:p" if the strings were singular and plural
respectively, "p:s" for plural and singular, and "p:p" for two distinct plurals. Inequal-
ity is indicated by returning an empty string.
It should be noted that two distinct singular words which happen to take the same plural
form are not considered equal, nor are cases where one (singular) word's plural is the
other (plural) word's singular. Hence all of the following return false:
PL_eq("base","basis") # ALTHOUGH BOTH -> "bases"
PL_eq("syrinx","syringe") # ALTHOUGH BOTH -> "syringes"
PL_eq("she","he") # ALTHOUGH BOTH -> "they"
PL_eq("opus","operas") # ALTHOUGH "opus" -> "opera" -> "operas"
PL_eq("taxi","taxes") # ALTHOUGH "taxi" -> "taxis" -> "taxes"
Note too that, although the comparison is "number-insensitive" it is not case-insensitive
(that is, "PL("time","Times")" returns false. To obtain both number and case insensitiv-
ity, prefix both arguments with "lc" (that is, "PL(lc "time", lc "Times")" returns true).
OTHER VERB FORMS
Present participles
"Lingua::EN::Inflect" also provides the "PART_PRES" subroutine, which can take a 3rd per-
son singular verb and correctly inflect it to its present participle:
PART_PRES("runs") # "running"
PART_PRES("loves") # "loving"
PART_PRES("eats") # "eating"
PART_PRES("bats") # "batting"
PART_PRES("spies") # "spying"
PROVIDING INDEFINITE ARTICLES
Selecting indefinite articles
Lingua::EN::Inflect provides two exportable subroutines ("A($;$)" and "AN($;$)") which
will correctly prepend the appropriate indefinite article to a word, depending on its pro-
nunciation. For example:
A("cat") # -> "a cat"
AN("cat") # -> "a cat"
A("euphemism") # -> "a euphemism"
A("Euler number") # -> "an Euler number"
A("hour") # -> "an hour"
A("houri") # -> "a houri"
The two subroutines are identical in function and may be used interchangeably. The only
reason that two versions are provided is to enhance the readability of code such as:
print "That is ", AN($errortype), " error\n;
print "That is ", A($fataltype), " fatal error\n;
Note that in both cases the actual article provided depends only on the pronunciation of
the first argument, not on the name of the subroutine.
"A()" and "AN()" will ignore any indefinite article that already exists at the start of
the string. Thus:
@half_arked = (
"a elephant",
"a giraffe",
"an ewe",
"a orangutan",
);
print A($_), "\n" for @half_arked;
# prints:
# an elephant
# a giraffe
# a ewe
# an orangutan
"A()" and "AN()" both take an optional second argument. As with the "PL_..." subroutines,
this second argument is a "number" specifier. If its value is 1 (or some other value
implying singularity), "A()" and "AN()" insert "a" or "an" as appropriate. If the number
specifier implies plurality, ("A()" and "AN()" insert the actual second argument instead.
For example:
A("cat",1) # -> "a cat"
A("cat",2) # -> "2 cat"
A("cat","one") # -> "one cat"
A("cat","no") # -> "no cat"
Note that, as implied by the previous examples, "A()" and "AN()" both assume that their
job is merely to provide the correct qualifier for a word (that is: "a", "an", or the
specified count). In other words, they assume that the word they are given has already
been correctly inflected for plurality. Hence, if $N has the value 2, then:
print A("cat",$N);
prints "2 cat", instead of "2 cats". The correct approach is to use:
print A(PL("cat",$N),$N);
or, better still:
print NO("cat",$N);
Note too that, like the various "PL_..." subroutines, whenever "A()" and "AN()" are called
with only one argument they are subject to the effects of any preceding call to "NUM()".
Hence, another possible solution is:
NUM($N);
print A(PL("cat"));
Indefinite articles and initialisms
"Initialisms" (sometimes inaccurately called "acronyms") are terms which have been formed
from the initial letters of words in a phrase (for example, "NATO", "NBL", "S.O.S.",
"SCUBA", etc.)
Such terms present a particular challenge when selecting between "a" and "an", since they
are sometimes pronounced as if they were a single word ("nay-tow", "sku-ba") and sometimes
as a series of letter names ("en-eff-ell", "ess-oh-ess").
"A()" and "AN()" cope with this dichotomy using a series of inbuilt rules, which may be
summarized as:
1. If the word starts with a single letter, followed by a period or dash (for exam-
ple, "R.I.P.", "C.O.D.", "e-mail", "X-ray", "T-square"), then choose the appropri-
ate article for the sound of the first letter ("an R.I.P.", "a C.O.D.", "an
e-mail", "an X-ray", "a T-square").
2. If the first two letters of the word are capitals, consonants, and do not appear
at the start of any known English word, (for example, "LCD", "XML", "YWCA"), then
once again choose "a" or "an" depending on the sound of the first letter ("an
LCD", "an XML", "a YWCA").
3. Otherwise, assume the string is a capitalized word or a pronounceable initialism
(for example, "LED", "OPEC", "FAQ", "UNESCO"), and therefore takes "a" or "an"
according to the (apparent) pronunciation of the entire word ("a LED", "an OPEC",
"a FAQ", "a UNESCO").
Note that rules 1 and 3 together imply that the presence or absence of punctuation may
change the selection of indefinite article for a particular initialism (for example, "a
FAQ" but "an F.A.Q.").
Indefinite articles and "soft H's"
Words beginning in the letter 'H' present another type of difficulty when selecting a
suitable indefinite article. In a few such words (for example, "hour", "honour", "heir")
the 'H' is not voiced at all, and so such words inflect with "an". The remaining cases
("voiced H's") may be divided into two categories: "hard H's" (such as "hangman", "holo-
graph", "hat", etc.) and "soft H's" (such as "hysterical", "horrendous", "holy", etc.)
Hard H's always take "a" as their indefinite article, and soft H's normally do so as well.
But some English speakers prefer "an" for soft H's (although the practice is now generally
considered an affectation, rather than a legitimate grammatical alternative).
At present, the "A()" and "AN()" subroutines ignore soft H's and use "a" for any voiced
'H'. The author would, however, welcome feedback on this decision (envisaging a possible
future "soft H" mode).
INFLECTING ORDINALS
Occasionally it is useful to present an integer value as an ordinal rather than as a
numeral. For example:
Enter password (1st attempt): ********
Enter password (2nd attempt): *********
Enter password (3rd attempt): *********
No 4th attempt. Access denied.
To this end, Lingua::EN::Inflect provides the "ORD()" subroutine. <ORD()> takes a single
argument and forms its ordinal equivalent. If the argument isn't a numerical integer, it
just adds "-th".
CONVERTING NUMBERS TO WORDS
The exportable subroutine "NUMWORDS" takes a number (cardinal or ordinal) and returns an
English representation of that number. In a scalar context a string is returned. Hence:
use Lingua::EN::Inflect qw( NUMWORDS );
$words = NUMWORDS(1234567);
puts the string:
"one million, two hundred and thirty-four thousand, five hundred and sixty-seven"
into $words.
In a list context each comma-separated chunk is returned as a separate element. Hence:
@words = NUMWORDS(1234567);
puts the list:
("one million",
"two hundred and thirty-four thousand",
"five hundred and sixty-seven")
into @words.
Non-digits (apart from an optional leading plus or minus sign, any decimal points, and
ordinal suffixes -- see below) are silently ignored, so the following all produce identi-
cal results:
NUMWORDS(5551202);
NUMWORDS(5_551_202);
NUMWORDS("5,551,202");
NUMWORDS("555-1202");
That last case is a little awkward since it's almost certainly a phone number, and "five
million, five hundred and fifty-one thousand, two hundred and two" probably isn't what's
wanted.
To overcome this, "NUMWORDS()" takes an optional named argument, 'group', which changes
how numbers are translated. The argument must be a positive integer less than four, which
indicated how the digits of the number are to be grouped. If the argument is 1, then each
digit is translated separately. If the argument is 2, pairs of digits (starting from the
left) are grouped together. If the argument is 3, triples of numbers (again, from the
left) are grouped. Hence:
NUMWORDS("555-1202", group=>1)
returns "five, five, five, one, two, zero, two", whilst:
NUMWORDS("555-1202", group=>2)
returns "fifty-five, fifty-one, twenty, two", and:
NUMWORDS("555-1202", group=>3)
returns "five fifty-five, one twenty, two".
Phone numbers are often written in words as "five..five..five..one..two..zero..two", which
is also easy to achieve:
join '..', NUMWORDS("555-1202", group=>1)
"NUMWORDS" also handles decimal fractions. Hence:
NUMWORDS("1.2345")
returns "one point two three four five" in a scalar context and
"("one","point","two","three","four","five")") in an array context. Exponent form
("1.234e56") is not yet handled.
Multiple decimal points are only translated in one of the "grouping" modes. Hence:
NUMWORDS(101.202.303)
returns "one hundred and one point two zero two three zero three", whereas:
NUMWORDS(101.202.303, group=>1)
returns "one zero one point two zero two point three zero three".
The digit '0' is unusual in that in may be translated to English as "zero", "oh", or
"nought". To cater for this diversity, "NUMWORDS" may be passed a named argument, 'zero',
which may be set to the desired translation of '0'. For example:
print join "..", NUMWORDS("555-1202", group=>3, zero=>'oh')
prints "five..five..five..one..two..oh..two". By default, zero is rendered as "zero".
Likewise, the digit '1' may be rendered as "one" or "a/an" (or very occasionally other
variants), depending on the context. So there is a 'one' argument as well:
print NUMWORDS($_, one=>'a solitary', zero=>'no more'),
PL(" bottle of beer on the wall\n", $_)
for (3,2,1,0);
# prints:
# three bottles of beer on the wall
# two bottles of beer on the wall
# a solitary bottle of beer on the wall
# no more bottles of beer on the wall
Care is needed if the word "a/an" is to be used as a 'one' value. Unless the next word is
known in advance, it's almost always necessary to use the "A" function as well:
print A( NUMWORDS(1, one=>'a') . " $_\n")
for qw(cat aardvark ewe hour);
# prints:
# a cat
# an aardvark
# a ewe
# an hour
Another major regional variation in number translation is the use of "and" in certain con-
texts. The named argument 'and' allows the programmer to specify how "and" should be han-
dled. Hence:
print scalar NUMWORDS("765", 'and'=>'')
prints "seven hundred sixty-five", instead of "seven hundred and sixty-five". By default,
the "and" is included.
The translation of the decimal point is also subject to variation (with "point", "dot",
and "decimal" being the favorites). The named argument 'decimal' allows the programmer to
how the decimal point should be rendered. Hence:
print scalar NUMWORDS("666.124.64.101", group=>3, decimal=>'dot')
prints "six sixty-six, dot, one twenty-four, dot, sixty-four, dot, one zero one" By
default, the decimal point is rendered as "point".
"NUMWORDS" also handles the ordinal forms of numbers. So:
print scalar NUMWORDS('1st');
print scalar NUMWORDS('3rd');
print scalar NUMWORDS('202nd');
print scalar NUMWORDS('1000000th');
print:
first
third
two hundred and twenty-second
one millionth
Two common idioms in this regard are:
print scalar NUMWORDS(ORD($number));
and:
print scalar ORD(NUMWORDS($number));
These are identical in effect, except when $number contains a decimal:
$number = 99.09;
print scalar NUMWORDS(ORD($number)); # ninety-ninth point zero nine
print scalar ORD(NUMWORDS($number)); # ninety-nine point zero ninth
Use whichever you feel is most appropriate.
INTERPOLATING INFLECTIONS IN STRINGS
By far the commonest use of the inflection subroutines is to produce message strings for
various purposes. For example:
print NUM($errors), PL_N(" error"), PL_V(" was"), " detected.\n";
print PL_ADJ("This"), PL_N(" error"), PL_V(" was"), "fatal.\n"
if $severity > 1;
Unfortunately the need to separate each subroutine call detracts significantly from the
readability of the resulting code. To ameliorate this problem, Lingua::EN::Inflect pro-
vides an exportable string-interpolating subroutine (inflect($)), which recognizes calls
to the various inflection subroutines within a string and interpolates them appropriately.
Using "inflect" the previous example could be rewritten:
print inflect "NUM($errors) PL_N(error) PL_V(was) detected.\n";
print inflect "PL_ADJ(This) PL_N(error) PL_V(was) fatal.\n"
if $severity > 1;
Note that "inflect" also correctly handles calls to the "NUM()" subroutine (whether inter-
polated or antecedent). The "inflect()" subroutine has a related extra feature, in that it
automatically cancels any "default number" value before it returns its interpolated
string. This means that calls to "NUM()" which are embedded in an "inflect()"-interpolated
string do not "escape" and interfere with subsequent inflections.
MODERN VS CLASSICAL INFLECTIONS
Certain words, mainly of Latin or Ancient Greek origin, can form plurals either using the
standard English "-s" suffix, or with their original Latin or Greek inflections. For exam-
ple:
PL("stigma") # -> "stigmas" or "stigmata"
PL("torus") # -> "toruses" or "tori"
PL("index") # -> "indexes" or "indices"
PL("millennium") # -> "millenniums" or "millennia"
PL("ganglion") # -> "ganglions" or "ganglia"
PL("octopus") # -> "octopuses" or "octopodes"
Lingua::EN::Inflect caters to such words by providing an "alternate state" of inflection
known as "classical mode". By default, words are inflected using their contemporary
English plurals, but if classical mode is invoked, the more traditional plural forms are
returned instead.
The exportable subroutine "classical()" controls this feature. If "classical()" is called
with no arguments, it unconditionally invokes classical mode. If it is called with a sin-
gle argument, it turns all classical inflects on or off (depending on whether the argument
is true or false). If called with two or more arguments, those arguments specify which
aspects of classical behaviour are to be used.
Thus:
classical; # SWITCH ON CLASSICAL MODE
print PL("formula"); # -> "formulae"
classical 0; # SWITCH OFF CLASSICAL MODE
print PL("formula"); # -> "formulas"
classical $cmode; # CLASSICAL MODE IFF $cmode
print PL("formula"); # -> "formulae" (IF $cmode)
# -> "formulas" (OTHERWISE)
classical herd=>1; # SWITCH ON CLASSICAL MODE FOR "HERD" NOUNS
print PL("wilderbeest"); # -> "wilderbeest"
classical names=>1; # SWITCH ON CLASSICAL MODE FOR NAMES
print PL("sally"); # -> "sallies"
print PL("Sally"); # -> "Sallys"
Note however that "classical()" has no effect on the inflection of words which are now
fully assimilated. Hence:
PL("forum") # ALWAYS -> "forums"
PL("criterion") # ALWAYS -> "criteria"
LEI assumes that a capitalized word is a person's name. So it forms the plural according
to the rules for names (which is that you don't inflect, you just add -s or -es). You can
choose to turn that behaviour off (it's on by the default, even when the module isn't in
classical mode) by calling " classical(names="0) >;
USER-DEFINED INFLECTIONS
Adding plurals at run-time
Lingua::EN::Inflect provides five exportable subroutines which allow the programmer to
override the module's behaviour for specific cases:
"def_noun($$)"
The "def_noun" subroutine takes a pair of string arguments: the singular and plu-
ral forms of the noun being specified. The singular form specifies a pattern to be
interpolated (as "m/^(?:$first_arg)$/i"). Any noun matching this pattern is then
replaced by the string in the second argument. The second argument specifies a
string which is interpolated after the match succeeds, and is then used as the
plural form. For example:
def_noun 'cow' => 'kine';
def_noun '(.+i)o' => '$1i';
def_noun 'spam(mer)?' => '\\$\\%\\@#\\$\\@#!!';
Note that both arguments should usually be specified in single quotes, so that
they are not interpolated when they are specified, but later (when words are com-
pared to them). As indicated by the last example, care also needs to be taken with
certain characters in the second argument, to ensure that they are not uninten-
tionally interpolated during comparison.
The second argument string may also specify a second variant of the plural form,
to be used when "classical" plurals have been requested. The beginning of the sec-
ond variant is marked by a '|' character:
def_noun 'cow' => 'cows|kine';
def_noun '(.+i)o' => '$1os|$1i';
def_noun 'spam(mer)?' => '\\$\\%\\@#\\$\\@#!!|varmints';
If no classical variant is given, the specified plural form is used in both normal
and "classical" modes.
If the second argument is "undef" instead of a string, then the current user defi-
nition for the first argument is removed, and the standard plural inflection(s)
restored.
Note that in all cases, later plural definitions for a particular singular form
replace earlier definitions of the same form. For example:
# FIRST, HIDE THE MODERN FORM....
def_noun 'aviatrix' => 'aviatrices';
# LATER, HIDE THE CLASSICAL FORM...
def_noun 'aviatrix' => 'aviatrixes';
# FINALLY, RESTORE THE DEFAULT BEHAVIOUR...
def_noun 'aviatrix' => undef;
Special care is also required when defining general patterns and associated spe-
cific exceptions: put the more specific cases after the general pattern. For exam-
ple:
def_noun '(.+)us' => '$1i'; # EVERY "-us" TO "-i"
def_noun 'bus' => 'buses'; # EXCEPT FOR "bus"
This "try-most-recently-defined-first" approach to matching user-defined words is
also used by "def_verb", "def_a" and "def_an".
"def_verb($$$$$$)"
The "def_verb" subroutine takes three pairs of string arguments (that is, six
arguments in total), specifying the singular and plural forms of the three "per-
sons" of verb. As with "def_noun", the singular forms are specifications of run-
time-interpolated patterns, whilst the plural forms are specifications of (up to
two) run-time-interpolated strings:
def_verb 'am' => 'are',
'are' => 'are|art",
'is' => 'are';
def_verb 'have' => 'have',
'have' => 'have",
'ha(s|th)' => 'have';
Note that as with "def_noun", modern/classical variants of plurals may be sepa-
rately specified, subsequent definitions replace previous ones, and "undef"'ed
plural forms revert to the standard behaviour.
"def_adj($$)"
The "def_adj" subroutine takes a pair of string arguments, which specify the sin-
gular and plural forms of the adjective being defined. As with "def_noun" and
"def_adj", the singular forms are specifications of run-time-interpolated pat-
terns, whilst the plural forms are specifications of (up to two) run-time-
interpolated strings:
def_adj 'this' => 'these',
def_adj 'red' => 'red|gules',
As previously, modern/classical variants of plurals may be separately specified,
subsequent definitions replace previous ones, and "undef"'ed plural forms revert
to the standard behaviour.
def_a($) and def_an($)
The "def_a" and "def_an" subroutines each take a single argument, which specifies
a pattern. If a word passed to "A()" or "AN()" matches this pattern, it will be
prefixed (unconditionally) with the corresponding indefinite article. For example:
def_a 'error';
def_a 'in.+';
def_an 'mistake';
def_an 'error';
As with the other "def_..." subroutines, such redefinitions are sequential in
effect so that, after the above example, "error" will be inflected with "an".
The $HOME/.inflectrc file
When it is imported, Lingua::EN::Inflect executes (as Perl code) the contents of any file
named .inflectrc which it finds in the in the directory where Lingua/EN/Inflect.pm is
installed, or in the current home directory ($ENV{HOME}), or in both. Note that the code
is executed within the Lingua::EN::Inflect namespace.
Hence the user or the local Perl guru can make appropriate calls to "def_noun",
"def_verb", etc. in one of these .inflectrc files, to permanently and universally modify
the behaviour of the module. For example
> cat /usr/local/lib/perl5/Text/Inflect/.inflectrc
def_noun "UNIX" => "UN*X|UNICES";
def_verb "teco" => "teco", # LITERALLY: "to edit with TECO"
"teco" => "teco",
"tecos" => "teco";
def_a "Euler.*"; # "Yewler" TURNS IN HIS GRAVE
Note that calls to the "def_..." subroutines from within a program will take precedence
over the contents of the home directory .inflectrc file, which in turn takes precedence
over the system-wide .inflectrc file.
DIAGNOSTICS
On loading, if the Perl code in a .inflectrc file is invalid (syntactically or otherwise),
an appropriate fatal error is issued. A common problem is not ending the file with some-
thing that evaluates to true (as the five "def_..." subroutines do).
Using the five "def_..." subroutines directly in a program may also result in fatal diag-
nostics, if a (singular) pattern or an interpolated (plural) string is somehow invalid.
Specific diagnostics related to user-defined inflections are:
"Bad user-defined singular pattern:\n\t %s"
The singular form of a user-defined noun or verb (as defined by a call to
"def_noun", "def_verb", "def_adj", "def_a" or "def_an") is not a valid Perl regu-
lar expression. The actual Perl error message is also given.
"Bad user-defined plural string: '%s'"
The plural form(s) of a user-defined noun or verb (as defined by a call to
"def_noun", "def_verb" or "def_adj") is not a valid Perl interpolated string (usu-
ally because it interpolates some undefined variable).
"Bad .inflectrc file (%s):\n %s"
Some other problem occurred in loading the named local or global .inflectrc file.
The Perl error message (including the line number) is also given.
There are no diagnosable run-time error conditions for the actual inflection subroutines,
except "NUMWORDS" and hence no run-time diagnostics. If the inflection subroutines are
unable to form a plural via a user-definition or an inbuilt rule, they just "guess" the
commonest English inflection: adding "-s" for nouns, removing "-s" for verbs, and no
inflection for adjectives.
"Lingua::EN::Inflect::NUMWORDS()" can "die" with the following messages:
"Bad grouping option: %s"
The optional argument to "NUMWORDS()" wasn't 1, 2 or 3.
"Number out of range"
"NUMWORDS()" was passed a number larger than
999,999,999,999,999,999,999,999,999,999,999,999 (that is: nine hundred and ninety-
nine decillion, nine hundred and ninety-nine nonillion, nine hundred and ninety-
nine octillion, nine hundred and ninety-nine septillion, nine hundred and ninety-
nine sextillion, nine hundred and ninety-nine quintillion, nine hundred and
ninety-nine quadrillion, nine hundred and ninety-nine trillion, nine hundred and
ninety-nine billion, nine hundred and ninety-nine million, nine hundred and
ninety-nine thousand, nine hundred and ninety-nine :-)
The problem is that "NUMWORDS" doesn't know any words for number components bigger
than "decillion".
OTHER ISSUES
2nd Person precedence
If a verb has identical 1st and 2nd person singular forms, but different 1st and 2nd per-
son plural forms, then when its plural is constructed, the 2nd person plural form is
always preferred.
The author is not currently aware of any such verbs in English, but is not quite arrogant
enough to assume ipso facto that none exist.
Nominative precedence
The singular pronoun "it" presents a special problem because its plural form can vary,
depending on its "case". For example:
It ate my homework -> They ate my homework
It ate it -> They ate them
I fed my homework to it -> I fed my homework to them
As a consequence of this ambiguity, "PL()" or "PL_N" have been implemented so that they
always return the nominative plural (that is, "they").
However, when asked for the plural of an unambiguously accusative "it" (namely, "PL("to
it")", "PL_N("from it")", "PL("with it")", etc.), both subroutines will correctly return
the accusative plural ("to them", "from them", "with them", etc.)
The plurality of zero
The rules governing the choice between:
There were no errors.
and
There was no error.
are complex and often depend more on intent rather than content. Hence it is infeasible
to specify such rules algorithmically.
Therefore, Lingua::EN::Text contents itself with the following compromise: If the govern-
ing number is zero, inflections always return the plural form unless the appropriate
"classical" inflection is in effect, in which case the singular form is always returned.
Thus, the sequence:
NUM(0);
print inflect "There PL(was) NO(choice)";
produces "There were no choices", whereas:
classical 'zero'; # or: classical(zero=>1);
NUM(0);
print inflect "There PL(was) NO(choice)";
it will print "There was no choice".
Homographs with heterogeneous plurals
Another context in which intent (and not content) sometimes determines plurality is where
two distinct meanings of a word require different plurals. For example:
Three basses were stolen from the band's equipment trailer.
Three bass were stolen from the band's aquarium.
I put the mice next to the cheese.
I put the mouses next to the computers.
Several thoughts about leaving crossed my mind.
Several thought about leaving across my lawn.
Lingua::EN::Inflect handles such words in two ways:
* If both meanings of the word are the same part of speech (for example,
"bass" is a noun in both sentences above), then one meaning is chosen as
the "usual" meaning, and only that meaning's plural is ever returned by
any of the inflection subroutines.
* If each meaning of the word is a different part of speech (for example,
"thought" is both a noun and a verb), then the noun's plural is returned
by "PL()" and "PL_N()" and the verb's plural is returned only by "PL_V()".
Such contexts are, fortunately, uncommon (particularly "same-part-of-speech" exam-
ples). An informal study of nearly 600 "difficult plurals" indicates that "PL()"
can be relied upon to "get it right" about 98% of the time (although, of course,
ichthyophilic guitarists or cyber-behaviouralists may experience higher rates of
confusion).
If the choice of a particular "usual inflection" is considered inappropriate, it
can always be reversed with a preliminary call to the corresponding "def_..." sub-
routine.
NOTE
I'm not taking any further correspondence on:
"octopi".
Despite the populist pandering of certain New World dictionaries, the plural is "octo-
puses" or (for the pendantic classicist) "octopodes". The suffix "-pus" is Greek, not
Latin, so the plural is "-podes", not "pi".
"virus".
Had no plural in Latin (possibly because it was a mass noun). The only plural is the
Anglicized "viruses".
AUTHORS
Damian Conway (damian AT conway.org) Matthew Persico (ORD inflection)
BUGS AND IRRITATIONS
The endless inconsistencies of English.
(Please report words for which the correct plural or indefinite article is not formed, so
that the reliability of Lingua::EN::Inflect can be improved.)
COPYRIGHT
Copyright (c) 1997-2000, Damian Conway. All Rights Reserved.
This module is free software. It may be used, redistributed
and/or modified under the same terms as Perl itself.
perl v5.8.8 2007-07-30 Lingua::EN::Inflect(3pm)
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