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There are a number of modules which convert numbers to words. I decided to try to reverse this process. The following is buggy and only handles numbers into the millions, but give the word_to_num function the string 'two hundred and ninety six million four hundred and twenty-two thousand five hundred and seventy eight point three four seven' and it will happily return 296422578.347.

This code is based on the parser outlined in "Higher Order Perl" by Dominus. Note that the docs for HOP::Parser are incomplete and you should refer to the book. It assumes the following grammar (there's a bug in the way it handles "zero". I should fix that at some point but this was just a quick hack).

# there's some looseness here to account for people's mangling # of the English language entire_input ::= numbers 'End_Of_Input' numbers ::= [ NEGATIVE ] millions | thousands | hundreds | tens | teens | on +es [ 'POINT' teens | ones { ones } ] millions ::= [ hundreds | teens | tens | ones ] 'MILLION' [ thousands | hundreds | teens | tens | ones ] thousands ::= [ hundreds | teens | tens | ones ] 'THOUSAND' [ hundreds | teens | tens | ones ] hundreds ::= [ teens | tens | ones ] 'HUNDRED' [ teens | tens | +ones ] tens ::= twenty | thirty | forty | fifty | sixty | seventy | eighty | ninety teens ::= ten | eleven | twelve | thirteen | fourteen | fifteen | sixteen | seventeen | eighteen | nineteen ones ::= zero | one | two | three | four | five | six | seven | eight | nine

Cheers,
Ovid

New address of my CGI Course.

And the code:

package Number::FromWord; use warnings; use strict; use HOP::Stream qw/iterator_to_stream/; use HOP::Lexer qw/make_lexer/; use HOP::Parser qw/:all/; use Regexp::Assemble; use Scalar::Util qw/looks_like_number/; use base 'Exporter'; our @EXPORT_OK = 'word_to_num'; my %one_num_for = ( zero => 0, one => 1, two => 2, three => 3, four => 4, five => 5, six => 6, seven => 7, eight => 8, nine => 9, ); my %teen_num_for = ( ten => 10, eleven => 11, twelve => 12, thirteen => 13, fourteen => 14, fifteen => 15, sixteen => 16, seventeen => 17, eighteen => 18, nineteen => 19, ); my %ten_num_for = ( twenty => 20, thirty => 30, forty => 40, fifty => 50, sixty => 60, seventy => 70, eighty => 80, ninety => 90, ); # # set up the lexer # my $ones_re = Regexp::Assemble->new; foreach my $number ( keys %one_num_for ) { $ones_re->add($number); } my $teens_re = Regexp::Assemble->new; foreach my $number ( keys %teen_num_for ) { $teens_re->add($number); } my $tens_re = Regexp::Assemble->new; foreach my $number ( keys %ten_num_for ) { $tens_re->add($number); } my @tokens = ( [ 'AND', qr/\band\b/i, sub { } ], [ 'MILLION', qr/million/i, \&number ], [ 'THOUSAND', qr/thousand/i, \&number ], [ 'HUNDRED', qr/hundred/i, \&number ], [ 'TENS', qr/$tens_re+/i, \&number ], [ 'TEENS', qr/$teens_re+/i, \&number ], [ 'ONES', qr/$ones_re+/i, \&number ], [ 'NEGATIVE', qr/negative/i ], [ 'POINT', qr/point/i ], [ 'SPACE', qr/[ -]/i, sub { } ], ); sub number { my ( $label, $number_as_word ) = @_; return [ $label, lc $number_as_word ]; } sub word_to_num { my @word = shift; my $lexer = make_lexer( sub { shift @word }, @tokens ); return parse($lexer); } # # set up the parser # my ( $numbers, $negative, $point, $ones, $teens, $tens, $hundreds, $thousands, $millions ); my $Point = parser { $point->(@_) }; my $Ones = parser { $ones->(@_) }; my $Teens = parser { $teens->(@_) }; my $Tens = parser { $tens->(@_) }; my $Hundreds = parser { $hundreds->(@_) }; my $Thousands = parser { $thousands->(@_) }; my $Millions = parser { $millions->(@_) }; my $Negative = parser { $negative->(@_) }; my $Numbers = parser { $numbers->(@_) }; # entire_input ::= numbers 'End_Of_Input' my $entire_input = T( concatenate( $Numbers, \&End_of_Input ), sub { s +hift } ); # numbers ::= [ NEGATIVE ] millions | thousands | hundreds | t +ens | teens | ones # [ 'POINT' teens | ones { ones } ] $numbers = T( concatenate( optional( lookfor('NEGATIVE') ), alternate( $Millions, $Thousands, $Hundreds, $Tens, $Teens, $O +nes ), optional( concatenate( absorb( lookfor('POINT') ), alternate( $Teens, concatenate( $Ones, star($Ones) ) ) ) ), ), sub { my ( $neg, $num, $point ) = @_; $point = $point->[0]; if ( looks_like_number($point) ) { # we have teens $num .= ".$point"; } elsif ( defined $point->[0] ) { # we have ones my $decimal = $point->[0]; if ( my @points = @{ $point->[1] } ) { $decimal .= join '', @points; } $num .= ".$decimal"; } if (@$neg) { $num *= -1; } return $num; } ); # millions ::= [ hundreds | teens | tens | ones ] # 'MILLION' # [ thousands | hundreds | teens | tens | ones ] $millions = T( concatenate( optional( alternate( $Hundreds, $Teens, $Tens, $Ones ) ), absorb( lookfor('MILLION') ), optional( alternate( $Thousands, $Hundreds, $Teens, $Tens, $On +es ) ) ), sub { my ( $million, $thousands ) = @_; $million = $million->[0] || 1; $thousands = $thousands->[0] || 0; return $million . sprintf "%06d", $thousands; } ); # thousands ::= [ hundreds | teens | tens | ones ] # 'THOUSAND' # [ hundreds | teens | tens | ones ] $thousands = T( concatenate( optional( alternate( $Hundreds, $Teens, $Tens, $Ones ) ), absorb( lookfor('THOUSAND') ), optional( alternate( $Hundreds, $Teens, $Tens, $Ones ) ) ), sub { my ( $thousand, $hundreds ) = @_; $thousand = $thousand->[0] || 1; $hundreds = $hundreds->[0] || 0; return $thousand . sprintf "%03d", $hundreds; } ); # hundreds ::= [ teens | tens | ones ] 'HUNDRED' [ teens | tens +| ones ] $hundreds = T( concatenate( optional( alternate( $Teens, $Tens, $Ones ) ), absorb( lookfor('HUNDRED') ), optional( alternate( $Teens, $Tens, $Ones ) ) ), sub { my ( $hundred, $tens ) = @_; $hundred = $hundred->[0] || 1; $tens = $tens->[0] || 0; return $hundred . sprintf "%02d", $tens; } ); # tens ::= 'TENS' [ ones ] $tens = T( concatenate( lookfor('TENS'), optional($Ones) ), sub { my ( $ten_word, $one_num ) = @_; my $ten_num = $ten_num_for{$ten_word}; $ten_num += $one_num->[0] || 0; return $ten_num; } ); # teens ::= 'TEENS' $teens = T( lookfor('TEENS'), sub { $teen_num_for{ $_[0] } } ); # ones ::= 'ONES' $ones = T( lookfor('ONES'), sub { $one_num_for{ $_[0] } } ); sub parse { my $stream = iterator_to_stream(shift); my ( $results, $remainder ) = eval { $entire_input->($stream) }; return $results; } 1;

This code also relies on the following functions with which I've extended the HOP::Parser: &absorb, &optional.

You didn't think I'd leave out tests, did you? Of course, they are rather incomplete.

#!perl #use Test::More tests => 1; use Test::More qw/no_plan/; BEGIN { chdir 't' if -d 't'; unshift @INC, '../lib'; use_ok( 'Number::FromWord', 'word_to_num' ); } can_ok __PACKAGE__, 'word_to_num'; my @words = ( 'three' => 3, 'fourteen' => 14, 'forty' => 40, 'forty-two' => 42, 'ninety nine' => 99, 'hundred' => 100, 'hundred and twenty' => 120, 'hundred and two' => 102, 'negative hundred and two' => -102, 'hundred ninety-nine' => 199, 'hundred nineteen' => 119, 'two hundred and three' => 203, 'twelve hundred and seventy three', => 1273, 'thousand' => 1000, 'seven hundred thirty-three thousand five hundred and twenty-nine' +, 733529, 'seventy three point two four five' => 73.245, 'three point seventeen' => 3.17, 'seven million' => 7000000, 'two hundred and ninety six million four hundred and twenty-two th +ousand five hundred and seventy eight', 296_422_578, 'two hundred and ninety six million four hundred and twenty-two th +ousand five hundred and seventy eight point three four seven', 296422578.347, ); while (@words) { my ( $word, $num ) = splice @words, 0, 2; is word_to_num($word), $num, "... $word should be $num"; }

In reply to Converting words to numbers with HOP::Parser by Ovid

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