vreIsSingleValue: Determine if a value range expression is a single value.
Description
vreIsSingleValue is a utility function that returns `TRUE` if the
specified value range expression is either numeric, a number expressed as
text or an expression of the form "v=" or "v==".
Usage
vreIsSingleValue(vre)
Arguments
vre
The value range expression to examine.
Value
`TRUE` if vre is a single value, `FALSE` otherwise.