$set_data_type [object]
$set_data_type sets the data type of a primitive data object.
OM(SingleWindowApp) -> prim x;
OM(SingleWindowApp) -> $help set_data_type
OM(SingleWindowApp) -> $set_data_type x float
OM(SingleWindowApp) -> $print x
float x;
OM(SingleWindowApp) -> $set_data_type x int
OM(SingleWindowApp) -> $print x
int x;