FoxPro functions which determine if a variable is a character string or a numeric string

Question

I'm looking for a Visual FoxPro function which is similar to the PHP function is_numeric().
I have found this, but I could not use VARTYPE or TYPE because the variable is always a character string which contains digits only.

I found ISDIGIT() function, but the manual says that it only checks the first character.

Determines whether the leftmost character of the specified character expression is a digit (0 through 9).

  ISDIGIT(cExpression)

Parameters
cExpression

Specifies the character expression that ISDIGIT( ) tests. Any characters after the first character in cExpression are ignored.

I would create my own function using the regular expression object VBScript.RegExp

FUNCTION isNumeric( tcValue )
    LOCAL oRE
    oRE = CreateObject("VBScript.RegExp")
    oRE.Pattern = '^[0-9]+$'
    RETURN oRE.test( tcValue )      
ENDFUNC

? isNumeric( '123' )

But, is there any function provided by FoxPro for this purpose?
Am I just overlooking?

Also same for ISALHPA() which determines whether the leftmost character in a character expression is alphabetic. I want to check if the variable contain only alphabets.

Solution 1

You can create your own function like this.

FUNCTION IsAllDigits
    LPARAMETERS tcSearched, tcOptionalSearch

    * tcSearched = the string of characters to test.
    * tcOptionalSearch = optional, additional characters to allow.

    LOCAL lcSearch
    m.lcSearch = "01234567989" + IIF(VARTYPE(m.tcOptionalSearch) = "C", m.tcOptionalSearch, "")

    LOCAL lcRemaining
    m.lcRemaining = CHRTRAN(m.tcSearched, m.lcSearch, "")

    RETURN ( LEN(m.lcRemaining) = 0 )
ENDFUNC

Solution 2

FUNCTION ISNUMERIC
    LPARAMETERS cVal
    LOCAL llNumeric, lnLen, lcChr, lnDecs, lnVal

    llNumeric = VARTYPE(cVal) = "N"      && Donkey has sent a numeric value
    lnDecs = 0

    DO CASE
        CASE llNumeric
        CASE VARTYPE(cVal)<>"C"          && Not a character
        OTHERWISE
            cVal = ALLTRIM(cVal)         && Trim spaces
            lnLen = LEN(cVal)            && How many characters
            llNumeric = .T.              && Assume
            i = 0
            DO WHILE llNumeric AND i<lnLen
                i = i+1
                lcChr = SUBSTR(cVal,i,1)        && Get next char
                    lnVal = VAL(lcChr)
                DO CASE
                CASE lcChr = "0"                && Allowed
                CASE lnVal>0                    && 1 - 9 OK
                CASE INLIST(lcChr, "-", "+")    && Allowed but ONLY at the start
                    llNumeric = i = 1
                CASE lcChr = "."                && Decimal point but ONLY one
                    lnDecs = lnDecs+1
                    llNumeric = lnDecs = 1
                OTHERWISE
                    llNumeric = .F.
            ENDCASE
        ENDDO
    ENDCASE
    RETURN llNumeric
ENDFUNC

Solution 3

This could work for ISDIGIT() or ISALPHA().

Function IsAllDigits(myValue)
   lReturn = .t. 
   FOR i = 1 TO LEN(myvalue)
      IF !ISDIGIT( SUBSTR(myValue, i, 1)  )
         lReturn = .f.
         EXIT
      ENDIF
   ENDFOR
   RETURN lReturn
ENDFUNC

Solution 4

How about a one liner?

Function IsNumeric
Lparameters pString
Return  m.pString == Chrtran(m.pString, Chrtran(m.pString, "0123456789", ""), "")
EndFunc

You can any other valid characters to "0123456789" like "." or ","

Solution 5

There is more simple to test if a string is numeric or not :

• If String="123" => val('String')>0
• If String="AB123" => val('String')=0

That's all...

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