WASP 🐝

a LISP programming language for extremely performant and concise web assembly modules

warning: this compiler is very alpha and error messages aren't the best, but it works and language is simple!

; main.w
(extern console_log [message])
(defn main "main" []
  (console_log "Hello World!")
)

wasp build

Features

• immutable c-strings, memory manipulation, global variables, imported functions
• optional standard library runtime
• functions with inline web assembly
• easy project dependency management
• self hosting
• macros
• code pruning and inlining
• test framework support
• type optional
• eval
• repl

Quickstart

Wasp depends on git and rust. Make sure you have them installed before beginning.

cargo install wasp
wasp init myproject
cd myproject
wasp build

At this point we will have a web assembly module with a single exported main function and nothing else

wasp add std https://github.com/wasmlang/std.git
wasp build

At this point we will have a web assembly module that has alot more access to the standard libraries functions and a default.

Drawing

Using wasm-module we can easily draw something to screen.

(extern global_getWindow [])
(extern Window_get_document [window])
(extern Document_querySelector [document query])
(extern HTMLCanvasElement_getContext [element context])
(extern CanvasRenderingContext2D_fillRect [canvas x y w h])

(defn main "main" []
  (let [
      window (global_getWindow)
      document (Window_get_document window)
      canvas (Document_querySelector document "#screen")
      ctx (HTMLCanvasElement_getContext canvas "2d")
    ]
      (CanvasRenderingContext2D_fillRect ctx 0 0 50 50)
    )
)

Mutable Global Data

It's often important for a web assembly modules to have some sort of global data that can be changed. For instance in a game we might have a high score.

(def high_score (data 0) )

(defn run_my_game
  ...
  (mem32 high_score (+ (mem32 high_score) 100)  
  ...
)

Project Management

Code dependencies are kept in a special folder called vendor which is populated by:

• copies of other folders on your system
• specific checkouts of git repositories.

For example a project.wasp containing:

foo = ../../foo
bar = git@github.com:richardanaya/bar.git@specific-bar

would result in these commands (roughly)

mkdir vendor
cp -R ../../foo vendor/foo
git clone git@github.com:richardanaya/bar.git@specific-bar vendor/bar

when wasp build is called

Now, when wasp compiles your code, it does a few things.

• In order specified by your project.wasp, one folder at a time all files ending in .w are loaded from each vendor/<dependency-name> and its subfolders.
• all files in the current directory and sub directories not in vendor are loaded
• as files are loaded, functions with same name as previous functions shadow the previous.

For example with project.wasp

foo = git@github.com:richardanaya/foo.git

assume my package foo has a function in its file at vendor/foo/foo.w:

...
(defn foo [] 123)
...

in my main.w I also have a foo function:

...
(defn foo [] 42)
...

because the vendor files are loaded in order before the main.w file in my project, I can override behavior from my vendor files resulting in a foo that returns 42 in my compile code.

This puts an onus on package makers to use good function names that properly include the namespace your package, but also gives the flexability to override very deep behavior pretty much anywhere.

wasp build --verbose

Can help you see what is shadowed if you have concerns.

Advanced

When necessary, low level web assembly can be directly inlined

(defn-wasm memswap [i32] [i32] ; 1 input, 1 output
  [i32]  ; int tmp = 0;
  ; tmp = a
  LOCAL_GET   0
  LOCAL_SET   2
  ; a = b
  LOCAL_GET   1
  LOCAL_SET   0
  ; b = tmp
  LOCAL_GET   2
  LOCAL_SET   1
  END
)

(defn main "main" []
  ...
  (memswap 10, 20)
)

Technical Details

Types

• integer - a 32-bit integer (e.g -1, 0, 42)
• string - a 32-bit pointer to a location in memory of the start of of a c-string (e.g. "hello world!")
• symbol - a 32-bit pointer to a location in memory of the start of of a c-string (e.g. ":hello_world")
• bool - a 32-bit number representing boolean values. True is 1, false is 0. (e.g. true false)
• empty - a 32-bit pointer to an empty value (e.g. ())
• data - a global only type this is a a 32-bit pointer to sequence of 32-bit values in memory (e.g. (data 1 true :hey (data :more-data ())). Use this for embedding raw data into your application memory on startup.

Functions

• (function-name ...) - call a function with arguments
• (mem x:integer) - get 8-bit value from memory location x
• (mem x:integer y) - set 8-bit value at memory location x to value y
• (mem32 x:integer) - get 32-bit value from memory location x
• (mem32 x:integer y) - set 32-bit value at memory location x to value y
• (if x y) - if x is true return expression y otherwise return empty
• (if x y z) - if x is true return expression y otherwise return expression z
• (do ... ) - executes a list of expressions and returns the value of the last. useful for multiple statement parameters.
• (let [x0:identifier y0:expression x1:identifier y1:expression ... ] ... ) - bind pairs of values to identifiers. Then run a sequence of expressions that can use those values by their identifier. Returns the value of the last expression in sequence. bindings specified in let shadow those at higher scopes.
• (loop ... x ) - evaluate a list of expressions again and again
• (break) - break out of current loop and return an empty value
• (continue) - restart execution at start of loop
• (+ ...) - sums a list of values and returns result
• (- ...) - subtracts a list of values and returns result
• (* ...) - multiplies a list of values and returns result
• (/ ...) - divides a list of values and returns result
• (% ...) - modulos a list of values and returns result
• (== x y) - returns true if values are equal, false if otherwise
• (!= x ) - returns true if values are not equal, false if otherwise
• (< x y) - returns true if x is less than y, false if otherwise
• (> x y) - returns true if x is greater than y, false if otherwise
• (<= x y) - returns true if x is less than or equal y, false if otherwise
• (>= x y) - returns true if x is greater than or equal y, false if otherwise
• (&& x y) - returns true if x and y are greater than zero, false if otherwise
• (|| x y) - returns true if x or y are greater than zero, false if otherwise
• (& x y) - returns bitwise and of x and y
• (| x y) - returns bitwise or of x and y
• (! x ) - returns true if zero and false if not zero
• (^ x ) - bitwise exclusive or of x
• (~ x ) - bitwise complement of x
• (<< x y) - shift x left by y bits
• (>> x y) - shift x right by y bits

Why so few functions?

Wasp prefers to keep as little in the core functionality as possible, letting the standard library evolve faster and more independent community driven manner. This project currently follows a principle that if a feature can be implemented with our primitive functions, don't include it in the core compiled language and let the standard library implement it. Also that no heap based concepts be added to the core language.

Notes

• all functions (including extern functions) return a value, if no obvious return, it is an empty value ()
• Web assembly global 0 is initialized to the end of the static data section (which might also be the start of a heap for a memory allocator). This value is immutable.
• Web assembly global lobal 1 also is initialized to the end of the static data section. This value is mutable and might be used to represent the end of your heap. Check out the simple allocator example.
• Literal strings create initialize data of a c-string at the front of your memory, and can be passed around as pointers to the very start in memory to your text. A \0 is automatically added at compile time, letting you easily have a marker to denote the end of your text.