Shen is a functional programming language that offers optional static type checking based on Sequent Calculus, Lisp macros, an integrated Prolog, an inbuilt compiler-compiler, pattern matching, Lambda Calculus consistency, and optional lazy evaluation.
Shen for iOS provides an offline interactive programming environment (REPL) based on Shen-C, which is fully conformant to the Shen standard test suite. A specialized keyboard is also provided to ease the input of symbols and special keys.