Datatype Functions

`IsBoolean`	Returns if a string can be interpreted as a localized boolean value.
`IsDate`	Returns if a string can be interpreted as a localized date.
`IsFloat`	Returns if a string can be interpreted as a localized floating point value.
`IsInteger`	Returns if a string can be interpreted as an integer value.
`IsLong`	Returns if a string can be interpreted as a 64-bits integer value.
`IsNull`	Returns if an expression is NULL.
`IsNumber`	Returns if an string can be interpreted as a number, i.e. an Integer, a Long or a Date.
`SizeOf`	Returns the memory used by a specific datatype.
`TypeOf`	Returns the datatype of an expression.