Transpiler¶

MOL can transpile .mol source code to Python or JavaScript.

Usage¶

mol transpile <file.mol> --target <python|javascript|js>

Python Target¶

mol transpile hello.mol --target python

Example¶

MOL source (example.mol):

let greeting be "Hello" |> upper
show greeting

define add(a, b)
  return a + b
end

show add(3, 4)

guard 7 > 5 : "Math is broken"

Python output:

from mol.types import *

greeting = upper("Hello")
print(greeting)

def add(a, b):
    return a + b

print(add(3, 4))

assert 7 > 5, "Math is broken"

JavaScript Target¶

mol transpile hello.mol --target javascript

JavaScript output:

let greeting = upper("Hello");
console.log(greeting);

function add(a, b) {
    return a + b;
}

console.log(add(3, 4));

if (!(7 > 5)) { throw new Error("Math is broken"); }

What Gets Transpiled¶

MOL Feature	Python	JavaScript
`show`	`print()`	`console.log()`
`let x be v`	`x = v`	`let x = v`
`set x to v`	`x = v`	`x = v`
`if/elif/else/end`	`if/elif/else:`	`if/else if/else {}`
`while/do/end`	`while:`	`while {}`
`for/in/do/end`	`for in:`	`for of {}`
`define/end`	`def:`	`function {}`
`\\|>` (pipe)	Nested calls	Nested calls
`guard`	`assert`	`if (!cond) throw`
`pipeline`	`def:`	`function {}`
`and/or/not`	`and/or/not`	`&&/\\|\\|/!`
`==` / `!=`	`==` / `!=`	`===` / `!==`

Pipe Chain Desugaring¶

The pipe operator is desugared into nested function calls:

MOL:

"hello" |> upper |> split(" ") |> len

Python:

len(split(upper("hello"), " "))

JavaScript:

len(split(upper("hello"), " "))

Limitations¶

Domain-specific operations (link, evolve, trigger, listen, emit) generate placeholder comments
access translates to a security check comment
Auto-tracing is not reproduced in transpiled output
Transpiled code may need MOL's type library for full functionality