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C-- (pronounced "see 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.
Design C-- is a "portable assembly language", designed to ease the task of implementing a compiler which produces high-quality machine code by having the compiler generate C-- code, delegating the harder work of low-level code generation and optimisation to a C-- compiler. Work on C-- began in the late 1990s. Since writing a custom code generator is a challenge in itself, and the compiler back ends 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 support tail recursion, accurate garbage collection or efficient exception handling. C-- is a simpler, tightly-defined alternative to C which does support all of these things. 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 language's syntax borrows heavily from C. It omits or changes standard C features such as variadic functions, pointer syntax, and aspects of C's type system, because they hamper certain essential features of C-- and the ease with which code-generation tools can produce it. 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 C++, "--" and "++" are operators meaning "subtract 1 from" and "add 1 to".) C-- is a target platform for the Glasgow Haskell Compiler, and an adaptation of C-- will eventually become the main code-generation path. Some of C--'s developers, including Simon Peyton Jones, Jo o Dias, and Norman Ramsey, also work or have worked on the Glasgow Haskell Compiler. The GHC codebase and development are based at Microsoft Research in Cambridge, though it is not a Microsoft project. Type system The C-- type system is deliberately designed to reflect constraints imposed by hardware rather than conventions imposed by higher-level languages. In C-- a value stored in a register or memory may have only one type: bit vector. However, bit vector is a polymorphic type and may come in several widths, e.g., bits8, bits32, or bits64. In addition to the bit-vector type C-- also provides a Boolean type bool, which can be computed by expressions and used for control flow but cannot be stored in a register or in memory. As in an assembly language, any higher type discipline, such as distinctions between signed, unsigned, float, and pointer, is imposed by the C-- operators or other syntactic constructs in the language. Sphinx C-- The name "C--" was also used for an earlier programming language developed in the 1990s by Peter Cellik for x86 computers. Sphinx C-- mixes C with x86 assembly language. See also External links de:C-- fa: fr:C-- (langage interm diaire) it:C-- no:C-- pl:C-- pt:C-- ru:C-- sl:C-- fi:C--
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