Soundex ( text )

MySQL's SOUNDEX() and the US Census Bureau's canonical American Soundex agree on H/W transparency and vowel-separation, but differ on one obscure rule: names where the first letter and second letter share the same code (like "Pfister", P=1/F=1). MySQL drops the F; the canonical spec also drops it — so no divergence there. The main thing to note in documentation is that this function matches MySQL's output, not the original Soundex patent, and non-ASCII characters are stripped silently.

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Joshua Paul - Show more from this author
Neo Code
http://www.neocode.com

Sample input:

Soundex ( "Ashcraft" )

Sample output:

A261

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

// Soundex ( text )
// Returns American Soundex code: 1 uppercase letter + up to 3 digits, zero-padded to 4.
// Matches MySQL SOUNDEX() output.
// Returns "" for empty or non-alpha input.
// Requires FM 18+ for While().
// Compatible: FM 18, 19, 20 (2023), 21 (2024).
//
// H/W rule: transparent — do not update prevCode.
// Vowel/Y rule: reset prevCode to "0" so same-coded
//   consonants separated by a vowel ARE both recorded.

Let ( [
    s         = Filter ( Upper ( text ) ; "ABCDEFGHIJKLMNOPQRSTUVWXYZ" ) ;
    codeTable = "01230120022455012623010202"
    // Position: Code(ch) - 64  (A→1 … Z→26)
    // A=0 B=1 C=2 D=3 E=0 F=1 G=2 H=0 I=0 J=2 K=2 L=4
    // M=5 N=5 O=0 P=1 Q=2 R=6 S=2 T=3 U=0 V=1 W=0 X=2 Y=0 Z=2
] ;

Case (
    IsEmpty ( s ) ; "" ;

    Let ( [
        firstChar = Left ( s ; 1 ) ;
        firstCode = Middle ( codeTable ; Code ( firstChar ) - 64 ; 1 )
    ] ;

    While (
        // Initial variables
        [ i        = 2 ;
          result   = firstChar ;
          prevCode = firstCode
        ] ;

        // Condition: more chars to process AND result not yet 4 chars
        i <= Length ( s ) and Length ( result ) < 4 ;

        // Logic (evaluated left-to-right; result uses old prevCode before prevCode updates)
        [ ch   = Middle ( s ; i ; 1 ) ;
          code = Middle ( codeTable ; Code ( ch ) - 64 ; 1 ) ;

          // Append digit: only if consonant (code ≠ "0") AND differs from previous code
          result = If ( code ≠ "0" and code ≠ prevCode ; result & code ; result ) ;

          // Update prevCode:
          //   consonant  → set to its code
          //   H or W     → transparent; leave prevCode unchanged
          //   vowel or Y → reset to "0"
          prevCode = Case (
              code ≠ "0"                         ; code ;
              Position ( "HW" ; ch ; 1 ; 1 ) > 0 ; prevCode ;
              "0"
          ) ;

          i = i + 1
        ] ;

        // Result: pad to 4 characters with trailing zeros
        Left ( result & "000" ; 4 )
    )
    )
)
)

The script Name it: Soundex_Test
No parameters needed. Requires no fields, no layout context.

# ============================================================
# Soundex_Test
# Runs 14 test cases against the Soundex() custom function.
# No fields or layout required. Results in Show Custom Dialog.
# FM 21 (v21) compatible.
# ============================================================

# --- Define test cases as return-delimited lists ---

Set Variable [ $inputs ;
Value:
"Robert" & ¶ &
"Rupert" & ¶ &
"Rubin" & ¶ &
"Ashcraft" & ¶ &
"Pfister" & ¶ &
"Tymczak" & ¶ &
"Honeyman" & ¶ &
"Washington" & ¶ &
"A" & ¶ &
"" & ¶ &
"123 !@#" & ¶ &
"O'Brien" & ¶ &
"Lloyd" & ¶ &
"Jackson"
]

Set Variable [ $expected ;
Value:
"R163" & ¶ &
"R163" & ¶ &
"R150" & ¶ &
"A261" & ¶ &
"P236" & ¶ &
"T522" & ¶ &
"H555" & ¶ &
"W252" & ¶ &
"A000" & ¶ &
"" & ¶ &
"" & ¶ &
"O165" & ¶ &
"L300" & ¶ &
"J250"
]

# --- Initialise counters and accumulators ---

Set Variable [ $total ; Value: ValueCount ( $inputs ) ]
Set Variable [ $pass ; Value: 0 ]
Set Variable [ $fail ; Value: 0 ]
Set Variable [ $i ; Value: 1 ]
Set Variable [ $report ; Value: "" ]

# --- Loop through each test case ---

Loop
Exit Loop If [ $i > $total ]

Set Variable [ $input ; Value: GetValue ( $inputs ; $i ) ]
Set Variable [ $exp ; Value: GetValue ( $expected ; $i ) ]
Set Variable [ $got ; Value: Soundex ( $input ) ]

# Display empty string inputs as in the report
Set Variable [ $label ;
Value: If ( IsEmpty ( $input ) ; "" ; $input )
]

If [ $got = $exp ]
Set Variable [ $pass ; Value: $pass + 1 ]
Set Variable [ $status ; Value: "PASS" ]
Else
Set Variable [ $fail ; Value: $fail + 1 ]
Set Variable [ $status ; Value: "FAIL ← got "" & $got & "" expected "" & $exp & """ ]
End If

Set Variable [ $report ;
Value:
$report &
$status & " " &
$label & " → " &
$exp & ¶
]

Set Variable [ $i ; Value: $i + 1 ]

End Loop

# --- Build summary header ---

Set Variable [ $summary ;
Value:
"Soundex() test results — FM 21" & ¶ &
"=================================" & ¶ &
"Total: " & $total &
" Pass: " & $pass &
" Fail: " & $fail & ¶ &
"=================================" & ¶ &
$report
]

# --- Show results ---

Show Custom Dialog [
Title: "Soundex Test Runner" ;
Message: $summary ;
Buttons: "OK"
]

-------------------------------------------------------------------------
Soundex() test results — FM 21
=================================
Total: 14 Pass: 14 Fail: 0
=================================
PASS Robert → R163
PASS Rupert → R163
PASS Rubin → R150
PASS Ashcraft → A261
PASS Pfister → P236
PASS Tymczak → T522
PASS Honeyman → H555
PASS Washington → W252
PASS A → A000
PASS →
PASS 123 !@# →
PASS O'Brien → O165
PASS Lloyd → L300
PASS Jackson → J250
---------------------------------------------------------------------------------
If a test fails it will look like:
FAIL ← got "T252" expected "T522" Tymczak → T522

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Soundex ( text )

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