Computes the exponential of the argument (e raised to the power of the argument.) This produces slightly more accurate results than the equivalent expression e**(argument).

Format: Exp(exprn)

Arguments:

- exprn (float): Expression to compute the exponential of.

Return type: float

Error conditions: Returns 'Bottom' if exprn evaluates to 'Bottom'.

Example:

`value = exp(4-var(0))
; Sets value to e raised to the quantity 4-var(0).`