Getting started

$ go get gitlab.com/thatzopoulos/lain
$ ./lain -h
Usage: lain [options] [<filename>]
  -d    enable debug mode
  -e string
        engine to use (eval or vm) (default "vm")
  -i    enable interactive mode
  -v    display version information
  

To execute a lain script simply pass the name to the interpreter:

$ ./lain ./scripts/hello.lain

Scripts can be made executable by adding a suitable shebang line:

$ cat hello.lain
#!/usr/bin/env lain
puts( "Hello, Lain!" );

Execution then works as you would expect:

$ chmod 755 hello.lain
$ ./hello.lain
Hello, Lain!
  

If a script is not passed into the interpreter, the user will be dropped into a REPL.

Language Details

Basic

s1 = "hello LAIN"                     // strings
i = 1000                              // int
b = true                              // bool
a = [1, "2"]                          // array
h = {"name": "Lain", "OS": "Copland"} // hash
n = null                              // null
let add = fn(a, b) { a + b };         // function
let newAdder = fn(x) { fn(y) { x + y } }; // closure
  

Types

Type      | Syntax                                    | Comments
--------- | ----------------------------------------- | -----------------------
null      | `null`                                    |
bool      | `true false`                              |
int       | 123                                       | a signed 64-bit integer
str       | `"" "foo" "foo"+"bar"`                    |
array     | `[] [1,2]`                                |
hashes    | `{"name": "Lain", "OS": "Copland"}`       |

Infix Operators

Arithmetic

5 + 5;
5 - 5;
5 * 5;
5 / 5;
  

Other

5 > 5;
5 < 5;
5 == 5;
5 != 5;
  

Prefix operators

!
-
  

Builtins

len() // Return the number of characters in a string
puts() // Takes an unlimited number of args, prints each on a separate line and returns null
push(array,value) // Returns a new array with value pushed onto the end of array
rest(array) // Returns a new array with the first element of array removed
first(array) // Returns the first element of the array
last(array) // Returns the last element of the array
  

Other Notes

Parameters in functions are evaluated from left to right. LAIN cannot make assertions about the order of argument evaluation.

Compiling an identifier is done with a 16-bit opcode instruction, so LAIN is limited to a maximum of 65536 global bindings.

Similarly, due to the 2 byte size of the OpArray opcode, the max number of elements that an array can hold is capped at 655355.

Syntax Highlighting Plugins For Various Text Editors

• lain.vim: vim plugin for LAIN
• lain.el: emacs plugin for LAIN
• lain.vscode: vscode plugin for LAIN