[$] The Koka programming language

Statically typed programming languages can help catch mismatches between the kinds ofvalues a program is intended to manipulate, and the values it actually manipulates.While there have been many bytes spent on discussions of whether this is worththe effort, some programming language designers believe that the type checkingin current languagesdoes not go far enough.Koka, anexperimental functional programming language, extends its type systemwith aneffect system that tracks the side-effects a program will have in thecourse of producing a value.