ObjectScript Reference \$ZEXP Exponential function (inverse of natural logarithm).
Synopsis
`\$ZEXP(n)`
Parameter
 n A number of any type. A number larger than 335.6 results in a error. A number smaller than -295.4 returns 0.
Description
\$ZEXP is the exponential function en, where e is the constant 2.718281828. Therefore, to return the value of e, you can specify \$ZEXP(1). \$ZEXP is the inverse of the natural logarithm function \$ZLN.
Parameter
n
Any number. It can be specified as a value, a variable, or an expression. A positive value larger than 335.6 or smaller than -4944763837 results in a <MAXNUMBER> error. A negative value smaller than -295.4 returns 0. A value of zero (0) returns 1. A non-numeric string is evaluated as 0 and therefore returns 1.
Examples
The following example demonstrates that \$ZEXP is the inverse of \$ZLN:
```  SET x=7
WRITE \$ZEXP(x),!
WRITE \$ZLN(x),!
WRITE \$ZEXP(\$ZLN(x))```
The following example returns \$ZEXP for negative and positive integers and for zero. This example returns the constant e as \$ZEXP(1):
```   FOR x=-3:1:3 {
WRITE !,"The exponential of ",x," = ",\$ZEXP(x)
}
QUIT```
returns:
```The exponential of -3 = .04978706836786394297
The exponential of -2 = .1353352832366126919
The exponential of -1 = .3678794411714423216
The exponential of 0 = 1
The exponential of 1 = 2.718281828459045236
The exponential of 2 = 7.389056098930650228
The exponential of 3 = 20.08553692318766774```
The following example uses IEEE floating point numbers (\$DOUBLE numbers). The first \$ZEXP returns a numeric value, the second \$ZEXP returns “INF” (or <MAXNUMBER> depending on the IEEEError() method setting):
```   SET rtn=##class(%SYSTEM.Process).IEEEError(0)
WRITE \$ZEXP(\$DOUBLE(1.0E2)),!
WRITE \$ZEXP(\$DOUBLE(1.0E3))```
The following example demonstrates that the empty string or a nonnumeric value is treated as 0:
```   WRITE \$ZEXP(""),!
WRITE \$ZEXP("INF")```
both return 1.