ISDIGIT()
 Determine if the leftmost character in a character string is a digit
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 Syntax

     ISDIGIT(<cString>) --> lBoolean

 Arguments

     <cString> is the character string to be examined.

 Returns

     ISDIGIT() returns true (.T.) if the first character of the character
     string is a digit between zero and nine; otherwise, it returns false
     (.F.).

 Description

     ISDIGIT() is a character function that determines whether the first
     character in a string is a numeric digit between zero and nine.  If any
     other character is the first character of the <cString>, ISDIGIT()
     returns false (.F.).

     ISDIGIT() is useful where you need to know if the current character
     string is a number before converting it to a numeric value with the
     VAL() function.

 Examples

     .  These examples demonstrate various results of ISDIGIT():

        ? ISDIGIT("AbcDe")         // Result: .F.
        ? ISDIGIT("1abcd")         // Result: .T.
        ? ISDIGIT(".12345")         // Result: .F.

 Files   Library is EXTEND.LIB.