There is no fundamental difference between compilers, code formatters, preprocessors or transpilers. Anything that takes a program and outputs another program r

There is no fundamental difference between compilers, code formatters, preprocessors or transpilers. Anything that takes a program and outputs another program related to it by some semantics is a compiler. That said though, I do agree that calling an assembler like this (brainfuck is a kind of assembly) a compiler stretches things a bit, for an entirely different reason: usually there is some sort of a complexity threshold of the input language. The compiler has to at least maintain a symbol table for named entities (traditional assemblies has variable-like entities, macros and subroutines, the assembler has to keep track of all that). Brainfuck is completely linear, with no named entities at all. The "compiler" looks like a dumb string processor, just iterates over one buffer to transform it into another buffer, and doesn't maintain any sort of structures on the code being translated. By the strict "compiler : program->program" definition, this doesn't matter. But my intuition holds that dumb string processing is a bit short of "true" compilation.