70 lines
2.2 KiB
Markdown
70 lines
2.2 KiB
Markdown
# chalk
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Chalk is a basic compiler from a toy language into CHIP-8 bytecode.
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It supports some higher-level constructs like looks and if-statements,
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and has some higher-level functions for drawing numbers and sprites.
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## Installation
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To compile chalk, simply run
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```Bash
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crystal build --release src/chalk.cr
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```
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## Usage
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### Syntax
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Chalk has minimal syntax. All code goes into functions, which are declared as follows:
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```
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fun function(param, another_param): return_type {
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}
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```
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All parameters are assumed to be of type `u8`, an unsigned byte.
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The return type can be either `u8` or `u0`, the latter being the same as `void` in C.
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Users can declare variables using the `var` keyword:
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```
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var name = 5;
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```
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Assigning to existing variables is performed as such:
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```
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name = 6;
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```
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It's possible to call another function, which uses the CHIP-8 stack. This stack
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is used exclusively for function calls, and may not exceed 12, as per the specifications
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of the CHIP-8 virtual machine.
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```
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var result = double(name);
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```
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Additionally, to ensure that user-defined variables stored
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in registers are not modified, chalk uses its own custom stack, placed at the end of the program.
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This stack is accessed by modifying a stack pointer register, which holds the offset from the beginning of the stack. Because CHIP-8 registers can only hold up 8-bit unsinged numbers, the stack is therefore limited to 254 items.
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If statements take "truthy" values to be those that have a nonzero value. As such,
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`if (0) {}` will never run, while `while(5) {}` will never terminate. Input can be awaited
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using the `get_key` function, which returns the number of the next key pressed.
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Sprites can be declared using a quasi-visual syntax:
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```
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sprite dum [
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` x x `
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` x x `
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` x x `
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` `
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`x x`
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` xxxxxx `
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]
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```
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These sprites can then be used in calls to `draw_sprite(sprite, x, y)`.
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## Contributing
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1. Fork it (<https://github.com/DanilaFe/chalk/fork>)
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2. Create your feature branch (`git checkout -b my-new-feature`)
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3. Commit your changes (`git commit -am 'Add some feature'`)
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4. Push to the branch (`git push origin my-new-feature`)
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5. Create a new Pull Request
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## Contributors
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- [DanilaFe](https://github.com/DanilaFe) Danila Fedorin - creator, maintainer
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