Earlier this month I gave a tech talk at Google, entitled “Tangible Functional Programming: a modern marriage of usability and composability”. Thanks to Google folks, the talk is now up on YouTube. I showed a way make functional programming “tangible” and visual, rather than abstract and syntactic and, in doing so, to fulfill the original Unix vision of simple, composable apps.
The key is to keep an app’s interface and functionality combined and separable. Combined yields usability, and separable yields composability. This principle applies not only to GUI-style interfaces, but to textual IO as well, and it applies to both direct composition and syntactic composition. See the TV page for examples of the latter. The common practice of mixing IO with functionality inhibits composability whether in C or in Haskell.