Compiler front end

A compiler front end reads a source language and checks or translates its meaning into a representation used by later compilation stages. lexical analysis groups characters into tokens; parsing builds structured syntax; name resolution and type checking establish which declarations and operations the program denotes. These responsibilities need not be implemented as completely separate passes.

For example, x + 2 * y must be grouped as x + (2 * y) under the usual precedence rules. The parser establishes that grouping, while semantic analysis determines whether x and y exist and support the requested operations. An abstract syntax tree can retain source locations for precise diagnostics. The LLVM Kaleidoscope tutorial shows this transition from parsed syntax to LLVM intermediate code.^[ref] The front end's language-facing checks complement the machine-facing decisions of a compiler back end.