# Compiler

A compiler takes in programs of a language, produces programs of a language.

If we think deeper, what are required of such a function?

A mapping! Different parts of the program should map to the output.

To get this different parts we use . Produces lexed IR which gives us our syntactic tokens, e.g. if, else, let.

Then we use to create an which has an interface we can work with. Produces parse tree IR. Note that loops are not considered because they still contain parse tree structure.

We then have to understand the of our source program,

and finally use to output program in target language.

More IRs may be produced through various phases: Typechecking, sem analysis, optimization, codegen.

Frontend - Machine independent parts. Backend - Machine dependent parts.

## Phases

• control-flow
• inlining of assembly as machine code
• Hardcodes memory allocations statically,
• Normal instructions get this during runtime

https://www.ibm.com/support/pages/what-does-it-mean-inline-function-and-how-does-it-affect-program

## Common tools used

• yacc, bison, (f)lex Not modern but stable. No inbuilt support for unicode.

• ANTLR Modern

• Definite clause grammars https://www.metalevel.at/prolog/dcg https://github.com/indocomsoft/aoc2020/blob/main/16/ans.pl http://csci431.artifice.cc/notes/prolog-parsing.html

• Parser combinators Combining various parsers.