transcompilation

Transcompilation is a form of program translation in which source code written in one programming language is converted into source code in another language at roughly the same level of abstraction. The process aims to preserve program structure and semantics as much as feasible, producing code that can be compiled or interpreted in a different runtime environment.

Unlike traditional compilation, which targets machine code or bytecode, transcompilation emphasizes translating language constructs rather than lowering to a different hardware target. It is related to source-to-source compilation and to the broader family of transpilers, tools that bridge languages to enable portability, modernization, or interoperability. Terminology varies, with transcompilation and transpilation often used interchangeably and transcompiler as the tool name.

Common examples include TypeScript to JavaScript and CoffeeScript to JavaScript, with Babel performing transformations from newer JavaScript syntax to widely supported versions. More substantial transcompilation includes enabling languages such as C/C++ or Rust to run in web environments by translating to JavaScript or WebAssembly, via toolchains that operate on intermediate representations like LLVM IR. Languages such as Haxe can target multiple languages, acting as transcompilers. Stylesheets and domain-specific languages also employ transcompilation, turning a higher-level language into a target language such as CSS.

Key considerations include fidelity of semantics, performance implications, debugging support and the availability of source maps, and compatibility of standard libraries between source and target languages. Transcompilation can simplify porting code to new platforms, enable modernization of legacy code, or allow use of different runtimes, but may introduce complexity and debugging challenges.