Some guidance in setting up Racket as a game scripting language.

[Hans Sjunnesson]

This is a hobby project of mine - a game in C, using SDL. I'd like to only use C for the rendering part - rather use a scripting language for all of the gameplay code. I want to try to use Racket for this - I've been doing enough Clojure that I'm familiar with a lisp. My first approach was to following along "Embedding into a Program" section of the Racket guide. But I'm running into road blocks - and I can't find any good examples of projects which embed Racket in a C program that calls functions in a Racket environment. My initial plan was to define a Racket module that provided an "init", an "update", and a "draw" function, then call those from the C program. The embedding guide points me to using "raco" to generate a C version of "racket/base", and that works - I can eval basic stuff, but I'm getting an error when I (require "test.rkt"). So I'm guessing there's more to be done with setting up the environment.

My "test.rkt" file is this:

#lang racket/base

(printf "Hello World!\n")

And this is the pertinent part of the main.c file, which links libracket.

#include "scheme.h"

#include "base.c"

static int run(Scheme_Env* e, int argc, char* argv[]) {

scheme_env = e;

declare_modules(e);

scheme_namespace_require(scheme_intern_symbol("racket/base"));

Scheme_Config* config = scheme_current_config();

Scheme_Object *curout = scheme_get_param(config, MZCONFIG_OUTPUT_PORT);

Scheme_Object* v = scheme_eval_string("(+ 1 2)", scheme_env);

scheme_display(v, curout);

scheme_display(scheme_make_char('\n'), curout);

scheme_eval_string("(require \"test.rkt\")", scheme_env);

  

  return 0;

}

int main(int argc, char* argv[]) {

scheme_main_setup(1, run, argc, argv);

return 0;

}

The output is:

3

standard-module-name-resolver: collection not found

  for module path: racket/base/lang/reader

  collection: "racket/base/lang"

  in collection directories:

  context...:

   show-collection-err_0

   standard-module-name-resolver

   1/module-path-index-resolve

   do-dynamic-require5_0

   read-syntax3_0

   default-load-handler

   standard-module-name-resolver

   1/module-path-index-resolve

   perform-require!78.1

   for-loop_0

   expand-capturing-lifts

   temp118_0

   temp91_0

   compile15_0

   temp85_0

I'm thinking that the environment isn't correctly setup here, the "in collection directories" lists is empty.

Am I going about this the wrong way though? Would I be better served in setting up all of the game loops, etc. in Racket, then use FFI just for rendering with SDL?

The game I'm making is a roguelike, so performance isn't as critical.

[Alex Harsanyi]

Unless your objective is to learn C and SDL, I would recommend writing the game entirely in Racket and using the Racket graphics facilities -- you will find that the performance will be more than enough for a roguelike game that you want to develop. Also, there are more people that can help you with Racket graphics questions, should you have any.

There is also a sdl2 package on pkgs.racket-lang.org, if you want to use SDL from Racket.

Alex.

[Hans Sjunnesson]

I get that it's probably not the best way of doing it, like I described it. But this is mostly a project of brushing up on C and more low level programming.

[Jens Axel Søgaard]

Den ons. 2. okt. 2019 kl. 15.31 skrev Hans Sjunnesson <hans.sj...@gmail.com>:

This is a hobby project of mine - a game in C, using SDL. I'd like to only use C for the rendering part - rather use a scripting language for all of the gameplay code. I want to try to use Racket for this - I've been doing enough Clojure that I'm familiar with a lisp. My first approach was to following along "Embedding into a Program" section of the Racket guide. But I'm running into road blocks - and I can't find any good examples of projects which embed Racket in a C program that calls functions in a Racket environment. My initial plan was to define a Racket module that provided an "init", an "update", and a "draw" function, then call those from the C program. The embedding guide points me to using "raco" to generate a C version of "racket/base", and that works - I can eval basic stuff, but I'm getting an error when I (require "test.rkt"). So I'm guessing there's more to be done with setting up the environment.

How do I compile the two test files?
In the reddit thread you said, I should start with:
raco ctool --c-mods base.c ++lib racket/base

But what are the options for gcc and the linker?

/Jens Axel

[Hans Sjunnesson]

I'm sorry Jens - I'm using Visual Studio on Windows to compile this project.

I've initially built libracket, and SDL, which I'm linking against.

I can zip the entire solution and upload it somewhere for you to have a look, but you'll need Visual Studio on Windows for that to work.

[Jens Axel Søgaard]

Den man. 7. okt. 2019 kl. 20.15 skrev Hans Sjunnesson <hans.sj...@gmail.com>:

I'm sorry Jens - I'm using Visual Studio on Windows to compile this project.

I've initially built libracket, and SDL, which I'm linking against.

I can zip the entire solution and upload it somewhere for you to have a look, but you'll need Visual Studio on Windows for that to work.

I don't have a windows machine - but your test example only have two files. Is there a way to see
what options are applied (in a log perhaps)?

/Jens Axel

 

[George Neuner]

Visual Studio's compile and link options are output in log files in the   <project_name>.tlog  sub-directory under the build (debug or release) directory.  See  CL.command.?.log  and  link.command.?.log  where '?' is some number.   [I don't know what that number represents - on my system I have only ever seen '1'.]

George

[George Neuner]

On 10/7/2019 4:30 PM, George Neuner wrote:

Visual Studio's compile and link options are output in log files in the   <project_name>.tlog  sub-directory under the build (debug or release) directory.  See  CL.command.?.log  and  link.command.?.log  where '?' is some number.   [I don't know what that number represents - on my system I have only ever seen '1'.]

Sorry, should have been a little more explicit.

By default the logs and build information are in the source tree in sub-directories that are named corresponding to the desired build:  debug, release, x64/debug, x64/release.  The  <project>.tlog directory and the logs for each build that has happened will be under those.

If the project is customized for different output locations, then YMMV.

George

[Hans Sjunnesson]

Thanks, that's helpful.

I've zipped the entire visual studio project and put it up here https://www.dropbox.com/s/v0taqj2zr0qdv8p/roguelike.zip?dl=0

You'll be able to find the tlog files here https://www.dropbox.com/s/v0taqj2zr0qdv8p/roguelike.zip?dl=0&file_subpath=%2Froguelike%2Fx64%2FDebug%2Froguelike.tlog

There's some SDL init stuff that pops a window with a texture on it. But in main.c, the program will throw an exception when trying this:

scheme_namespace_require(scheme_make_utf8_string("test.rkt"));

If you comment that, it works - and you can evaluate racket code like this:

scheme_eval_string("(+ 1 2)", scheme_env);