[ordu]

> A "compiler" is software that translates computer code from one programming language into another language.

Yes, of course.

> Literally all it can express is linear functions.

And why a language to express linear functions can't be a programming language?

> My fixed-function calculator is more powerful than that!

But it isn't compiling, it is interpreting, is it? So your fixed-function calculator is not a compiler, it is an interpreter. It is irrelevant how powerful it is. There are much even more powerful interpreters and less powerful compilers.

The example we see gets computer code in one language and translates it into machine instructions. Talking about 'understatement' you are adding to this definition more constraints and these are very fuzzy constraints on what counts as a programming language.