NAME¶
Lingua::EN::Inflect - Convert singular to plural. Select "a" or
"an".
VERSION¶
This document describes version 1.895 of Lingua::EN::Inflect
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
WORDLIST
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, $word2);
print "same noun\n" if PL_N_eq($word1, $word2);
print "same verb\n" if PL_V_eq($word1, $word2);
print "same adj.\n" if PL_ADJ_eq($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"
# LITERAL STYLE ONLY NAMES NUMBERS LESS THAN A CERTAIN THRESHOLD...
$words = NUMWORDS( 9, threshold=>10); # "nine"
$words = NUMWORDS( 10, threshold=>10); # "ten"
$words = NUMWORDS( 11, threshold=>10); # "11"
$words = NUMWORDS(1000, threshold=>10); # "1,000"
# JOIN WORDS INTO A LIST:
$list = WORDLIST("apple", "banana", "carrot");
# "apple, banana, and carrot"
$list = WORDLIST("apple", "banana");
# "apple and banana"
$list = WORDLIST("apple", "banana", "carrot", {final_sep=>""});
# "apple, banana and carrot"
# 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
appropriate, "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 initialisms.
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").
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 grammatical "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 preferred to the (singular) verb sense.
Hence "PL("knife")" will return "knives"
("knife" having been treated as a singular 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.
Wordy and comma'd plurals
The "NO()" subroutine takes an optional third argument: a hash of
named options that configure its behaviour.
The 'words_below' option informs "NO()" what other numbers (i.e. apart
from zero) it should convert to words. For example:S
for my $count (0..12) {
print NO('cat', $count, {words_below => 10}), "\n";
}
would print:
no cats
one cat
two cats
three cats
four cats
five cats
six cats
seven cats
eight cats
nine cats
10 cats
11 cats
12 cats
The 'comma' and 'comma_every' options determine whether or not the numbers
produced by "NO()" have commas in them. That is:
2001 space odysseys
versus:
2,001 space odysseys
Normally, numbers are produced without commas, but if 'comma' or 'comma_every'
is specified, then commas are added as requested.
The 'comma' option specifies which character to use as a comma. It defaults to
',', but may be set to anything convenient:
print NO('Euro', $amount, {comma=>'.'});
# prints: 1.000.000 Euros
The 'comma_every' option specifies how many characters between commas. It
defaults to 3, but may be set to any positive number:
print NO('Euro', $amount, {comma_every=>4});
# prints: 100,0000 Euros
Note that you can set both options at once, if you wish:
print NO('Euro', $amount, {comma_every=>2, comma=>'_'});
# prints: 1_00_00_00 Euros
Reducing the number of counts required¶
In some contexts, the need to supply an explicit count to the various
"PL_..." subroutines makes for tiresome repetition. For example:
print PL_ADJ("This",$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 subsequently 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 differing 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:
- •
- the strings are "eq"-equal, or
- •
- one string is "eq"-equal to a plural form of the other, or
- •
- 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. Inequality 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 insensitivity, prefix both arguments with "lc"
(that is, "PL(lc "time", lc "Times")" returns
true).
Present participles¶
"Lingua::EN::Inflect" also provides the "PART_PRES"
subroutine, which can take a 3rd person 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 pronunciation. 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
example, "R.I.P.", "C.O.D.", "e-mail",
"X-ray", "T-square"), then choose the appropriate
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", "holograph",
"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 identical 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') . " $_\n")
for qw(cat aardvark ewe hour);
# prints:
# a cat
# an aardvark
# a ewe
# an hour
Another major regional variation in number translation is the use of
"and" in certain contexts. The named argument 'and' allows the
programmer to specify how "and" should be handled. Hence:
print scalar NUMWORDS("765", 'and'=>'')
prints "seven hundred sixty-five", instead of "seven hundred and
sixty-five". By default, the "and" is included.
The translation of the decimal point is also subject to variation (with
"point", "dot", and "decimal" being the
favorites). The named argument 'decimal' allows the programmer to how the
decimal point should be rendered. Hence:
print scalar NUMWORDS("666.124.64.101", group=>3, decimal=>'dot')
prints "six sixty-six, dot, one twenty-four, dot, sixty-four, dot, one zero
one" By default, the decimal point is rendered as "point".
"NUMWORDS" also handles the ordinal forms of numbers. So:
print scalar NUMWORDS('1st');
print scalar NUMWORDS('3rd');
print scalar NUMWORDS('202nd');
print scalar NUMWORDS('1000000th');
print:
first
third
two hundred and twenty-second
one millionth
Two common idioms in this regard are:
print scalar NUMWORDS(ORD($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($number)); # ninety-nine point zero ninth
Use whichever you feel is most appropriate.
CONVERTING LISTS OF WORDS TO PHRASES¶
When creating a list of words, commas are used between adjacent items, except if
the items contain commas, in which case semicolons are used. But if there are
less than two items, the commas/semicolons are omitted entirely. The final
item also has a conjunction (usually "and" or "or") before
it. And although it's technically incorrect (and sometimes misleading), some
people prefer to omit the comma before that final conjunction, even when there
are more than two items.
That's complicated enough to warrant its own subroutine: "WORDLIST()".
This subroutine expects a list of words, possibly with one or more hash
references containing options. It returns a string that joins the list
together in the normal English usage. For example:
print "You chose ", WORDLIST(@selected_items), "\n";
# You chose barley soup, roast beef, and Yorkshire pudding
print "You chose ", WORDLIST(@selected_items, {final_sep=>""}), "\n";
# You chose barley soup, roast beef and Yorkshire pudding
print "Please chose ", WORDLIST(@side_orders, {conj=>"or"}), "\n";
# Please chose salad, vegetables, or ice-cream
The available options are:
Option named Specifies Default value
conj Final conjunction "and"
sep Inter-item separator ","
last_sep Final separator value of 'sep' option
INTERPOLATING INFLECTIONS IN STRINGS¶
By far the commonest use of the inflection subroutines is to produce message
strings for various purposes. For example:
print NUM($errors), PL_N(" error"), PL_V(" was"), " detected.\n";
print PL_ADJ("This"), PL_N(" error"), PL_V(" was"), "fatal.\n"
if $severity > 1;
Unfortunately the need to separate each subroutine call detracts significantly
from the readability of the resulting code. To ameliorate this problem,
Lingua::EN::Inflect provides an exportable string-interpolating subroutine
(inflect($)), 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 interpolated 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 example:
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 single 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 plural 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 compared 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 unintentionally 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 second 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 definition 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
specific exceptions: put the more specific cases after the general
pattern. For example:
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($$$$$$)"
- The "def_verb" subroutine takes three pairs of string arguments
(that is, six arguments in total), specifying the singular and plural
forms of the three "persons" of verb. As with
"def_noun", the singular forms are specifications of
run-time-interpolated patterns, whilst the plural forms are specifications
of (up to two) run-time-interpolated strings:
def_verb 'am' => 'are',
'are' => 'are|art",
'is' => 'are';
def_verb 'have' => 'have',
'have' => 'have",
'ha(s|th)' => 'have';
Note that as with "def_noun", modern/classical variants of plurals
may be separately specified, subsequent definitions replace previous ones,
and "undef"'ed plural forms revert to the standard
behaviour.
- "def_adj($$)"
- The "def_adj" subroutine takes a pair of string arguments, which
specify the singular and plural forms of the adjective being defined. As
with "def_noun" and "def_adj", 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_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 something that evaluates to true (as the
five "def_..." subroutines do).
Using the five "def_..." subroutines directly in a program may also
result in fatal diagnostics, 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 regular
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 (usually 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 person 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 governing 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" examples). 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_..." subroutine.
NOTE¶
I'm not taking any further correspondence on:
- "octopi".
- Despite the populist pandering of certain New World dictionaries, the
plural is "octopuses" or (for the pedantic 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@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) 1997-2009, 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.