Example of linear interpolation (lerp) in Vyper.
Values change linearly from y0 to y1 over the time span of t0 to t1.
#pragma version 0.4.0
y0: public(uint256)
y1: public(uint256)
t0: public(uint256)
t1: public(uint256)
@deploy
def __init__():
self.y0 = 10
self.y1 = 20
self.t0 = block.timestamp + 30
self.t1 = block.timestamp + 60
@external
def lerp() -> uint256:
return self._lerp(self.y0, self.y1, self.t0, self.t1, block.timestamp)
@internal
def _lerp(y0: uint256, y1: uint256, x0: uint256, x1: uint256, x: uint256) -> uint256:
assert x0 < x1
if x <= x0:
return y0
if x >= x1:
return y1
# w(x) = (x - x0) / (x1 - x0)
# f(x) = y0*(1 - w(x)) + y1*w(x)
# = (y0*((x1 - x0) - (x - x0)) + y1*(x - x0)) / (x1 - x0)
x1_x: uint256 = x1 - x
x_x0: uint256 = x - x0
x1_x0: uint256 = x1 - x0
return (y0*x1_x + y1*x_x0) // x1_x0
