78 lines
2.5 KiB
Perl
78 lines
2.5 KiB
Perl
package DDG::Goodie::NoteFrequency;
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# ABSTRACT: Return the frequency (Hz) of the note given in the query
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use DDG::Goodie;
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use strict;
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zci answer_type => "note_frequency";
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zci is_cached => 1;
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# Triggers
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triggers any => "notefreq", "notefrequency", "note frequency", "note frequency of", "frequency of note";
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# Handle statement
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handle remainder => sub {
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return unless $_;
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# must be a note letter, optional sharp or flat,
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# octave number, optional tuning frequency for A4,
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# and optional case-insensitive "hz" with or without preceding whitespace
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# e.g. "g#3 432 hz" or "ab5 435Hz"
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return unless ($_ =~ /^([A-Ga-g])([b#])?([0-8])(\s+[0-9]{1,4})?(\s?[hH][zZ])?$/ );
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my( $letter, $accidental, $octave, $tuning, $pitchClass, $midi, $frequency );
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# regex captures
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if (defined $1) { $letter = uc($1); } else { $letter = ""; }
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if (defined $2) { $accidental = $2; } else { $accidental = ""; }
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if (defined $3) { $octave = $3 + 0; } else { $octave = 0; }
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if (defined $4) { $tuning = $4 + 0; } else { $tuning = 0; }
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# assume 440Hz tuning unless otherwise specified
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if ( $tuning == 0 ) { $tuning = 440; }
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# convert note letter to pitch class number
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if ( $letter eq "C" ) { $pitchClass = 0; }
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elsif ( $letter eq "D" ) { $pitchClass = 2; }
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elsif ( $letter eq "E" ) { $pitchClass = 4; }
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elsif ( $letter eq "F" ) { $pitchClass = 5; }
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elsif ( $letter eq "G" ) { $pitchClass = 7; }
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elsif ( $letter eq "A" ) { $pitchClass = 9; }
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else { $pitchClass = 11; }
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# apply accidental to pitch class number
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if ( $accidental eq "b" ) { $pitchClass -= 1; }
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elsif ( $accidental eq "#" ) { $pitchClass += 1; }
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# calculate MIDI number
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$midi = ( 12 * ($octave + 1) ) + $pitchClass;
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# fix pitch class number
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$pitchClass %= 12;
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# validate note is between C0 and B8
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return unless ( $midi >= 12 && $midi <= 119 );
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# calculate frequency
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$frequency = $tuning * ( 2 ** (($midi-69)/12) );
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# round to two decimal places (is never negative anyway and avoids libs)
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$frequency = int(100 * ($frequency + 0.005)) / 100;
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# result
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return $frequency,
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structured_answer => {
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data => {
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title => $frequency." Hz",
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subtitle => "Note Frequency: $letter$accidental$octave in A$tuning tuning",
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},
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templates => {
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group => 'text',
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},
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};
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};
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1;
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