Ivy is an interpreter for an APL-like language. It is a plaything and a work in progress.
Documentation at http://godoc.org/robpike.io/ivy. Try the demo: cd demo; go run demo.go
Prototype apps for iPhone, iPad, and Android are available in the App store and Google Play store. Search for "ivy bignum calculator".
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 The talk predates a lot of the features, including floating point, text, and user-defined operators.
To be built, ivy requires Go 1.5.