Alice (programming language)

Alice ML is a programming language designed by the Programming Systems Laboratory at Saarland University, Saarbrücken, Germany. It is a dialect of Standard ML, augmented with support for lazy evaluation, concurrency (multithreading and distributed computing via remote procedure calls) and constraint programming.

Alice extends Standard ML in a number of ways that distinguish it from its predecessor. Alice provides concurrency features as part of the base language through the use of a future type that represents a value being provided by an independent thread of execution. A thread that uses a future value will block on an attempt to access the value until the thread performing it has completed the computation. A related concept is also provided termed a promise, allowing a thread to provide a future value that it will compute to another thread. Future and promise typed variables are used to implement data-flow synchronizing.

As does the Haskell functional language, Alice also provides facilities to allow using a lazy evaluation strategy in programs, versus the traditional eager evaluation strategy of Standard ML. While Haskell uses the lazy model by default, Alice uses an eager evaluation model by default, needing an explicit programming statement for a computation to evaluate lazily.

The Alice implementation from Saarland University uses the Simple Extensible Abstract Machine (SEAM) virtual machine. It is free software, and features just-in-time compilation to bytecode and native code for the x86 architecture.