ObjectScript Reference
$ISVALIDDOUBLE


Validates a $DOUBLE numeric value and returns a boolean; optionally provides range checking.
Synopsis
$ISVALIDDOUBLE(num,scale,min,max)
The
$ISVALIDDOUBLE function determines whether
num passes validation tests for an IEEE doubleprecision floating point number and returns a boolean value. It optionally performs a range check using
min and
max values, which are automatically converted to IEEE numbers. The
scale parameter is used during range checking to specify how many fractional digits to compare. A boolean value of 1 means that
num is a properly formed IEEE doubleprecision number value and passes the range check, if one is specified.
$ISVALIDDOUBLE is a validation function; it does not determine if
num is a number of data type DOUBLE, or if it has been generated using the
$DOUBLE function.
$ISVALIDDOUBLE validates American format numbers, which use a period (.) as the decimal separator. It does not validate European format numbers, which use a comma (,) as the decimal separator.
$ISVALIDDOUBLE does not consider valid a number that contains numeric group separators; it returns 0 (invalid) for any number containing a comma or a blank space, regardless of the current locale.
The number to be validated may be an integer, a fractional number, a number in scientific notation (with the letter “E” or “e”). It may be a string, expression, or variable that resolves to a number. It may be signed or unsigned, and may contain leading or trailing zeros.
ObjectScript converts a number to
canonical form before supplying it to
$ISVALIDDOUBLE for validation. Therefore, any arithmetic expression, numeric concatenation, or multiple leading + and – signs are resolved prior to evaluation by the function. ObjectScript does not convert a numeric string to canonical form prior to evaluation. However, prefacing a numeric string with a + sign forces numeric evaluation (and thus canonical conversion) of a
numeric string.

num contains any characters other than the digits 0–9, a leading + or – sign, a decimal point (.), and a letter “E” or “e”.

num contains more than one + or – sign, decimal point, or letter “E” or “e”. If
num is a number, ObjectScript resolves multiple leading + and – signs. If
num is a numeric string, it cannot contain more than one leading + or – sign.

The optional + or – sign is not the first character of
num.

The letter “E” or “e” indicating a base10 exponent is not followed by an integer in a numeric string. With a number, “E” not followed by an integer results in a <SYNTAX> error.

If
num is INF (with or without a + or – sign), it is a valid
$DOUBLE number; the boolean value returned by
$ISVALIDDOUBLE depends on whether
num passes the specified range check.
The
scale parameter is used during range checking to specify how many fractional digits to compare. Specify an integer value for
scale; any fractional digits in the
scale value are ignored. You can specify a
scale value larger than the number of fractional digits specified in the other parameters. You can specify a
scale value of –1; all other negative
scale values result in a <FUNCTION> error.
A nonnegative
scale value causes
num to be rounded to that number of fractional digits before performing
min and
max range checking. A
scale value of 0 causes
num to be rounded to an integer value (3.9 = 4) before performing range checking. A
scale value of –1 causes
num to be truncated to an integer value (3.9 = 3) before performing range checking. To compare all specified digits without rounding or truncating, omit the
scale parameter. A
scale value that is nonnumeric or the null string is equivalent to a
scale value of 0.
Rounding is performed for all
scale values except –1. A value of 5 or greater is always rounded up.
The
scale parameter value causes evaluation using rounded or truncated versions of the
num value. The actual value of the
num variable is not changed by
$ISVALIDDOUBLE processing.
If you omit the
scale parameter, retain the comma as a place holder.
You can specify a minimum allowed value, a maximum allowed value, neither, or both. If specified, the
num value (after the
scale operation) must be greater than or equal to the
min value, and less than or equal to the
max value. The values are converted to IEEE floating point numbers before being used for range checking. A null string as a
min or
max value is equal to zero. If a value does not meet these criteria,
$ISVALIDDOUBLE returns 0.
The NAN value is always valid, regardless of the
min or
max value.
If you omit a parameter, retain the comma as a place holder. For example, when omitting
scale and specifying
min or
max, or when omitting
min and specifying
max. Trailing commas are ignored.
In the following example, each invocation of
$ISVALIDDOUBLE returns 1 (valid number):
WRITE !,$ISVALIDDOUBLE(0) ; All integers OK
WRITE !,$ISVALIDDOUBLE(4.567) ; Fractional numbers OK
WRITE !,$ISVALIDDOUBLE("4.567") ; Numeric strings OK
WRITE !,$ISVALIDDOUBLE(.0) ; Signed numbers OK
WRITE !,$ISVALIDDOUBLE(+123) ; Multiple signs resolved for numbers OK
WRITE !,$ISVALIDDOUBLE(+004.500) ; Leading/trailing zeroes OK
WRITE !,$ISVALIDDOUBLE(4E2) ; Scientific notation OK
In the following example, each invocation of
$ISVALIDDOUBLE returns 0 (invalid number):
WRITE !,$ISVALIDDOUBLE("") ; Null string is invalid
WRITE !,$ISVALIDDOUBLE("4,567") ; Commas are not permitted
WRITE !,$ISVALIDDOUBLE("4A") ; Invalid character
WRITE !,$ISVALIDDOUBLE("+123") ; Multiple signs not resolved for strings
In the following example, each invocation of
$ISVALIDDOUBLE returns 1 (valid number), even though INF (infinity) and NAN (Not A Number) are, strictly speaking, not numbers:
WRITE !,$ISVALIDDOUBLE($DOUBLE($ZPI)) ; DOUBLE numbers OK
WRITE !,$ISVALIDDOUBLE($DOUBLE("INF")) ; DOUBLE INF OK
WRITE !,$ISVALIDDOUBLE($DOUBLE("NAN")) ; DOUBLE NAN OK
In the following example, specifying a
min value eliminates INF but not INF:
WRITE !,$ISVALIDDOUBLE($DOUBLE("INF"),,99999999999)
WRITE !,$ISVALIDDOUBLE($DOUBLE("INF"),,99999999999)
The following example shows the use of the
min and
max parameters. All of the following return 1 (number is valid and also passes the range check):
WRITE !,$ISVALIDDOUBLE(4,,3,5) ; scale can be omitted
WRITE !,$ISVALIDDOUBLE(4,2,3,5) ; scale can be larger than
; number of fractional digits
WRITE !,$ISVALIDDOUBLE(4,0,,5) ; min or max can be omitted
WRITE !,$ISVALIDDOUBLE(4,0,4,4) ; min and max are inclusive
WRITE !,$ISVALIDDOUBLE(4,0,5,5) ; negative numbers
WRITE !,$ISVALIDDOUBLE(4.00,2,04,05) ; leading/trailing zeros
WRITE !,$ISVALIDDOUBLE(.4E3,0,3E2,400) ; base10 exponents expanded
The following example shows the use of the
scale parameter with
min and
max. All of the following return 1 (number is valid and also passes the range check):
WRITE !,$ISVALIDDOUBLE(4.55,,4.54,4.551)
; When scale is omitted, all digits of num are checked.
WRITE !,$ISVALIDDOUBLE(4.1,0,4,4.01)
; When scale=0, num is rounded to an integer value
; (0 fractional digits) before min & max check.
WRITE !,$ISVALIDDOUBLE(3.85,1,3.9,5)
; num is rounded to 1 fractional digit,
; (with values of 5 or greater rounded up)
; before min check.
WRITE !,$ISVALIDDOUBLE(4.01,17,3,5)
; scale can be larger than number of fractional digits.
WRITE !,$ISVALIDDOUBLE(3.9,1,2,3)
; When scale=1, num is truncated to an integer value
$ISVALIDDOUBLE and $ISVALIDNUM Compared

Both functions accept as valid numbers the INF, –INF, and NAN values returned by
$DOUBLE.
$ISVALIDDOUBLE also accepts as valid numbers the not casesensitive strings “NAN” and “INF”, as well as the variants “Infinity” and “sNAN”, and any of these strings beginning with a single plus or minus sign.
$ISVALIDNUM rejects all of these strings as invalid, and returns 0.
WRITE !,$ISVALIDNUM($DOUBLE("NAN")) ; returns 1
WRITE !,$ISVALIDDOUBLE($DOUBLE("NAN")) ; returns 1
WRITE !,$ISVALIDNUM("NAN") ; returns 0
WRITE !,$ISVALIDDOUBLE("NAN") ; returns 1

Both functions parse signed and unsigned integers (including –0), scientific notation numbers (with “E” or “e”), real numbers (123.45) and numeric strings (“123.45”).

Neither function recognizes the European DecimalSeparator character (comma (,)) or the NumericGroupSeparator character (American format: comma (,); European format: period (.)). For example, both reject the string “123,456” as an invalid number, regardless of the current locale setting.

Both functions parse multiple leading signs (+ and –) for numbers. Neither accepts multiple leading signs in a quoted numeric string.