Numbers in scripts are interpreted as either int or float, depending on decimal point. This must be kept in mind when assigning very large or very small constants or constant expressions to a variable. You can find details in the manual under "Variables". This has nothing to do with the bit size of a double.
So the problem was not "what" i assign to a var - the question is "how" i do that. I do now understand that in var a = value; the value (a constant) is either int or float.
I was thinking the manual means only the following situation, "assigning a constant to a var":
#define INP_TEST 1024.000123231
var a = INP_TEST;
Sorry my bad
, but why you did not say that earlier