From Io example below I would say it's a little different. It's more like it has a runtime api to change/generate it's runtime. I think SmallTalk has something similar to this.
In Io, all code is data. Below is an example of changing a functions behaviour (from addition to subtraction):
Io> plus := block (a, b, a + b)
==> method(a, b,
a + b
)
Io> plus call (1, 2)
==> 3
Io> plus message next setName ("-")
==> -(b)
Io> plus
==> method(a, b,
a - b
)
Io> plus call (1, 2)
==> -1