Wrong computation of time elapsing

[etienneandre]

The following operation:

elapsing (x1) in
	(
	x_1 = 3
		 & x_1 >= 0
	)

gives x_1 = 3

which is wrong (it should be x_1 >= 3).

[etienneandre]

In fact, this comes from the use of "_" in variable names. The computation is correct if x_1 is replaced with x1.