How to test if string is numeric using Progress 4GL - progress-4gl

Question

Does Progress 4GL have a function for testing whether a string is numeric, like PHP's is_numeric($foo) function?
I've seen the function example at http://knowledgebase.progress.com/articles/Article/P148549 to test if a character in a string is numeric. Looks like it has a typo, btw.
But I would think the language would be a built-in function for this.

Answer 1

I was looking at this myself recently. The approved answer given to this doesn't work in 100% situations.
If the user enters any of the following special string characters: ? * - or + the answer won't work.
A single plus or minus(dash) is converted to 0 which you may not want.
A single question mark character is valid value which progress recognises as unknown value at which again you may not want.
A single or group asterisks on their own also get converted to 0.
If you run the following code you'll see what I mean.
DISP DECIMAL("*")
DECIMAL("**")
DECIMAL("?")
DECIMAL("+")
DECIMAL("-").
The following additional code maybe useful to get around this
DEFINE VARIABLE iZeroCode AS INTEGER NO-UNDO.
DEFINE VARIABLE iNineCode AS INTEGER NO-UNDO.
DEFINE VARIABLE chChar AS CHARACTER NO-UNDO.
ASSIGN iZeroCode = ASC("0")
iNineCode = ASC("9")
chChar = SUBSTRING(cNumber,1,1).
IF NOT(ASC(chChar) >= iZeroCode AND ASC(chChar) <= iNineCode) THEN DO:
MESSAGE "Invalid Number..." VIEW-AS ALERT-BOX.
END.

Answer 2

Do not need a function can jsut do a straight conversion.
ASSIGN dNumber = DECIMAL(cNumber) NO-ERROR.
IF ERROR-STATUS:ERROR THEN
DO:
{Handle issues}
END.
or if it is always whole numbers can use INTEGER instead of DECIMAL.

Answer 3

The language does not have a built-in "isNum()" type of function.
An alternative to the kbase method would be:
function isNum returns logical ( input s as character ):
define variable n as decimal no-undo.
assign
n = decimal( s )
no-error
.
return ( error-status:num-messages = 0 ).
end.
display isNum( "123" ) isNum( "xyz" ).

Answer 4

This code handles any numeric strings - even if the used Character is longer than the max Decimal length etc.
FUNCTION isNumeric RETURNS LOGICAL (textvalue AS CHAR):
DEF VAR i AS INT NO-UNDO.
IF textvalue = ? THEN RETURN TRUE.
DO i = 1 TO (LENGTH(textvalue) - 1):
INT(SUBSTRING(textvalue, i, (i + 1))) NO-ERROR.
IF ERROR-STATUS:ERROR THEN RETURN FALSE.
END.
RETURN TRUE.
END FUNCTION.

Answer 5

Works 100% of the time
FUNCTION is-num RETURNS LOGICAL
(INPUT cString AS CHARACTER):
DEFINE VARIABLE iZeroCode AS INTEGER NO-UNDO.
DEFINE VARIABLE iNineCode AS INTEGER NO-UNDO.
DEFINE VARIABLE cChar AS CHARACTER NO-UNDO.
DEFINE VARIABLE iCount AS INTEGER NO-UNDO.
DO iCount = 1 TO LENGTH(cString):
ASSIGN iZeroCode = ASC("0")
iNineCode = ASC("9")
cChar = SUBSTRING(cString,iCount,1).
IF NOT(ASC(cChar) >= iZeroCode AND ASC(cChar) <= iNineCode) THEN DO:
RETURN FALSE.
END.
END.
RETURN TRUE.
END.