Sunday, November 05, 2017

Writing a Simple DSL Compiler with Delphi [7. AST Compiler]

This article provides a description of an AST compiler used for my toy language project. If you are new to this series, I would recommend to start reading with this post. At least you should read the previous post, Intermezzo, as it explains some parts of the compiler that I won't touch here.

Please note that this article describes an initial implementation of the compiler. If you want to browse the code while reading the article, make sure that you have switched to branch dsl_v1.

In my toy compiler framework, a compiler (or codegen as it is called internally), is a piece of code that implements the ISimpleDSLCodegen interface. This interface exposes only one function, Generate, which takes an abstract syntax tree and converts it into an object implementing an ISimpleDSLProgram interface which allows you to call any function in a compiled program by name.

  TParameters = TArray;
  TFunctionCall = reference to function (const parameters: TParameters): integer;
  ISimpleDSLProgram = interface ['{2B93BEE7-EF20-41F4-B599-4C28131D6655}']
    function  Call(const functionName: string; const params: TParameters;       var return: integer): boolean;

  ISimpleDSLCodegen = interface ['{C359C174-E324-4709-86EF-EE61AFE3B1FD}']
    function Generate(const ast: ISimpleDSLAST;      
runnable: ISimpleDSLProgram): boolean;