Impure range expressions

[robinsierra]

Version Information

• vyper Version: 0.1.0b9
• Tested with Remix IDE

Currently Vyper allows range expressions of the form range(x, x + n) where n is a constant. A weird case happens when x is impure:

glob: int128

@public
def foo() -> int128:
	self.glob += 1
	return 5


@public
def bar():
	for i in range(self.foo(), self.foo() + 1):
		pass

Even though the range expression contains two calls to self.foo() it is only executed once, which feels very unintuitive at best. In general, it would be nice to have some documentation for loops/range expressions (especially if this is the intended behavior).

[jacqueswww]

I agree, I don't think this should be allowed at all, ie. functions called in range() have to be @constant.