# lerp method

Size lerp (Size a, Size b, double t)

Linearly interpolate between two sizes

If either size is null, this function interpolates from Size.zero.

The `t` argument represents position on the timeline, with 0.0 meaning that the interpolation has not started, returning `a` (or something equivalent to `a`), 1.0 meaning that the interpolation has finished, returning `b` (or something equivalent to `b`), and values in between meaning that the interpolation is at the relevant point on the timeline between `a` and `b`. The interpolation can be extrapolated beyond 0.0 and 1.0, so negative values and values greater than 1.0 are valid (and can easily be generated by curves such as `Curves.elasticInOut`).

Values for `t` are usually obtained from an `Animation<double>`, such as an `AnimationController`.

## Implementation

    static Size lerp(Size a, Size b, double t) {
      assert(t != null);
      if (a == null && b == null)
        return null;
      if (a == null)
        return b * t;
      if (b == null)
        return a * (1.0 - t);
      return new Size(lerpDouble(a.width, b.width, t), lerpDouble(a.height, b.height, t));
    }