Ivy is an interpreter for an APL-like language. It is a plaything and a work in progress.
To be built, it requires Go 1.5, which is in beta at the time of writing.
A prototype App for iPhone and iPad is available in the App store. Search for "ivy bignum calculator".
Full documentation at: http://godoc.org/robpike.io/ivy
Slides for a talk at: http://go-talks.appspot.com/github.com/robpike/ivy/talks/ivy.slide Video for the talk at: http://www.youtube.com/watch?v=PXoG0WX0r_E