| Lingua::EN::Inflect - Convert singular to plural. Select "a" or "an". |
Lingua::EN::Inflect - Convert singular to plural. Select ``a'' or ``an''.
This document describes version 1.86 of Lingua::EN::Inflect, released October 20, 2000.
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"
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).
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($;$)PL_N() takes a singular English noun or
pronoun and returns its plural. Pronouns in the nominative (``I'' ->
``we'') and accusative (``me'' -> ``us'') cases are handled, as are
possessive pronouns (``mine'' -> ``ours'').
PL_V($;$)PL_V() takes the singular form of a
conjugated verb (that is, one which is already in the correct ``person''
and ``mood'') and returns the corresponding plural conjugation.
PL_ADJ($;$)PL_ADJ() takes the singular form of
certain types of adjectives and returns the corresponding plural form.
Adjectives that are correctly handled include: ``numerical'' adjectives
(``a'' -> ``some''), demonstrative adjectives (``this'' -> ``these'', ``that'' ->
``those''), and possessives (``my'' -> ``our'', ``cat's'' -> ``cats''', ``child's''
-> ``childrens''', etc.)
PL($;$)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 ''.
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 $N had the value zero, the previous example
would print the somewhat more elegant:
I saw no animals
rather than:
I saw 0 animals
Note that the name of the subroutine is a pun: the subroutine
returns either a number (a No.) or a "no", in front of the
inflected word.
In some contexts, the need to supply an explicit count to the various
PL_... subroutines makes for tiresome repetition. For example:
print PL_ADJ("This",$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;
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:
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).
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"
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"));
``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:
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.'').
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).
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''.
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 C<'one'> value.
Unless the next word is known in advance, it's almost always necessary
to use the C<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($number)); # ninety-nine point zero ninth
Use whichever you feel is most appropriate.
By far the commonest use of the inflection subroutines is to produce message strings for various purposes. For example:
print NUM($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.
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) >;
Lingua::EN::Inflect provides five exportable subroutines which allow the programmer to override the module's behaviour for specific cases:
def_noun($$)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($$$$$$)def_verb subroutine takes three pairs of string arguments (that is, six
arguments in total), specifying the singular and plural forms of the three
``persons'' of verb. As with def_noun, the singular forms are specifications of
run-time-interpolated patterns, whilst the plural forms are specifications of
(up to two) run-time-interpolated strings:
def_verb 'am' => 'are',
'are' => 'are|art",
'is' => 'are';
def_verb 'have' => 'have',
'have' => 'have",
'ha(s|th)' => 'have';
Note that as with def_noun, modern/classical variants of plurals
may be separately specified, subsequent definitions replace previous
ones, and undef'ed plural forms revert to the standard behaviour.
def_adj($$)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($) and def_an($)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''.
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.
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"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'"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"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"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''.
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.
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 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''.
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:
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.
I'm not taking any further correspondence on:
Damian Conway (damian@conway.org) Matthew Persico (ORD inflection)
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 (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.
| Lingua::EN::Inflect - Convert singular to plural. Select "a" or "an". |