From 0251a3319532a30b3f7583a8fbde0f4591762c02 Mon Sep 17 00:00:00 2001 From: David Thompson Date: Sun, 8 Jan 2023 09:08:07 -0500 Subject: Add skeleton of Seagull compiler. --- chickadee/graphics/seagull.scm | 115 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) create mode 100644 chickadee/graphics/seagull.scm diff --git a/chickadee/graphics/seagull.scm b/chickadee/graphics/seagull.scm new file mode 100644 index 0000000..505c4b4 --- /dev/null +++ b/chickadee/graphics/seagull.scm @@ -0,0 +1,115 @@ +;;; Chickadee Game Toolkit +;;; Copyright © 2023 David Thompson +;;; +;;; Chickadee is free software: you can redistribute it and/or modify +;;; it under the terms of the GNU General Public License as published +;;; by the Free Software Foundation, either version 3 of the License, +;;; or (at your option) any later version. +;;; +;;; Chickadee is distributed in the hope that it will be useful, but +;;; WITHOUT ANY WARRANTY; without even the implied warranty of +;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +;;; General Public License for more details. +;;; +;;; You should have received a copy of the GNU General Public License +;;; along with this program. If not, see +;;; . + +;;; Commentary: +;; +;; Seagull is a purely functional, statically typed, Scheme-like +;; language that can be compiled to GLSL code. +;; +;; Notable features and restrictions: +;; - Vertex and fragment shader output +;; - Lexical scoping (of course) +;; - Targets multiple GLSL versions +;; - Multiple return values +;; - Type inference +;; - Nested functions (but no free non-top-level variables) +;; - Tail recursion allowed, but no other recursion +;; +;;; Code: +(define-module (chickadee graphics seagull) + #:use-module (ice-9 format) + #:use-module (ice-9 match) + #:use-module (srfi srfi-9) + #:export (compile-seagull)) + +;; The Seagull compiler is designed as a series of source-to-source +;; program transformations in which each transformation pass results +;; in a program that is one step closer to being directly emitted to +;; GLSL code. + + +;;; +;;; Alpha conversion +;;; + +;; Alpha conversion is the process of converting all the user defined +;; identifiers in a program to uniquely named identifiers. This +;; process frees the compiler from having to worry about things like +;; '+' being a user defined variable that shadows the primitive +;; addition operation. + + +;;; +;;; Macro expansion +;;; + +;; Macro expansion converts convenient but non-primitive syntax forms +;; (such as let*) into primitive syntax. Seagull does not currently +;; support user defined macros, just a set of built-ins. + + +;;; +;;; Free variable annotation +;;; + +;; All lambda forms are annotated with the variables that appear free +;; in their body expressions. Unfortunately, GLSL does not allow +;; nested function definitions, so nested functions in Seagull only +;; allow free variable references for top-level variables, such as +;; shader inputs and uniforms. + + +;;; +;;; Function hoisting +;;; + +;; Move all non-top-level lambda bindings to the top-level. As +;; mentioned earlier, GLSL does not allow nested functions. + + +;;; +;;; Explicit tail call marking +;;; + +;; Make note of which function calls are in tail position. GLSL does +;; not allow for recursive function calls, but Seagull allows them in +;; tail position only because they can be compiled to a loop in GLSL. + + +;;; +;;; Type inference +;;; + +;; Transform all program expressions into typed expressions by +;; applying a variant of the Hindley-Milner type inference algorithm. +;; GLSL is a statically typed language, but thanks to type inference +;; Seagull code doesn't need type annotations. + + +;;; +;;; GLSL emission +;;; + +;; Transform typed expressions into a string of GLSL code. + + +;;; +;;; Compiler front-end +;;; + +;; Combine all of the compiler passes on a user provided program and +;; emit GLSL code if the program is valid. -- cgit v1.2.3