C-- (pronounced C minus minus) is a C-like programming language. Its creators, functional programming researchers Simon Peyton Jones and Norman Ramsey, designed it to be generated mainly by compilers for very high-level languages rather than written by human programmers. Unlike many other intermediate languages, its representation is plain ASCII text, not bytecode or another binary format. There are two main branches: C--, the original branch, with the final version 2.0 released in May 2005 Cmm, the fork actively used as the intermediate representation (IR) in the Glasgow Haskell Compiler (GHC) Design C-- is a "portable assembly language", designed to ease the implementation of compilers that produce high-quality machine code. This is done by delegating low-level code-generation and program optimization to a C-- compiler. The language's syntax borrows heavily from C while omitting or changing standard C features such as variadic functions, pointer syntax, and aspects of C's type system, because they hamper essential features of C-- and ease of code-generation. The name of the language is an in-joke, indicating that C-- is a reduced form of C, in the same way that C++ is basically an expanded form of C. (in C, -- and ++ mean "decrement" and "increment," respectively.) Work on C-- began in the late 1990s. Since writing a custom code generator is a challenge in itself, and the compiler backends available to researchers at that time were complex and poorly documented, several projects had written compilers which generated C code (for instance, the original Modula-3 compiler). However, C is a poor choice for functional languages: it does not guarantee tail-call optimization, or support accurate garbage collection or efficient exception handling. C-- is a tightly-defined simpler alternative to C which supports all of these. Its most innovative feature is a run-time interface which allows writing of portable garbage collectors, exception handling systems and other run-time features which work with any C-- compiler. The first version of C-- was released in April 1998 as a MSRA paper, accompanied by a January 1999 paper on garbage collection. A revised manual was posted in HTML form in May 1999. Two sets of major changes proposed in 2000 by Norman Ramsey ("Proposed Changes") and Christian Lindig ("A New Grammar") led to C-- version 2, which was finalized around 2004 and officially released in 2005. Type system The C-- type system is designed to reflect constraints imposed by hardware rather than conventions imposed