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Ask HN: Transpiling a dynamically typed language to a statically typed language

5 points by leksak ↗ HN
Hi, I have been pondering what I want to do for my master thesis (2+ years away) and I have an idea. I am writing to ask if the question has a known answer or is even theoretically possible to conduct.

My idea is to write a source-to-source compiler from a Lisp_2 to Rust, but I do not know if it is possible to transpile from a dynamic language to a statically typed language. Is it?

9 comments

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malisper
In one of the later chapters, the book Lisp in Small Pieces (great book), shows you how to write a a Scheme compiler to C. The general idea is you create a structure that contains a union type of all types in the dynamic language, and also a tag that tells you which type it is.
[dead] mc_hammer
its much easier if you can skip int8 and int16 and just use a single precision, if not consider a shorthand syntax for them like "u1234" or "d1234" or "foo = uint(1234)".

for libraries you can get the types from the library headers, "func a(foo int)" you know that x is int if they write "a(x)"

for new code just check the values assigned to variables (through all time); 1-10 as int, 1.xx-10.xx as float, etc. then use some switching to fill in the rest. but it never catches all the edge cases so you maybe you can use a foo<type> custom-syntax...

i did something similar for coffeescript to golang and i could get about 99% but i know it would break under real world conditions, ended with a custom syntax foo#type or foo<type>, and then they can use int8 and int16 and double and what not.

ryanlm
My honest opinion is that unless you've written C, or assembly, I don't consider you a real programmer.
leksak
What does this have to do, at all, with the question?
bbcbasic
Thats a true Scotsman argument.
nakkaya
It is possible. Some scheme compilers use C as their intermediate language. Scheme to C to binary. (Gambit/Chicken/Stalin etc.). I have a project [1][2] that compiles a subset of Clojure to C++11 that is written using literate programming [3]. It thoroughly documented and should give you an idea on how to build your own.

[1] http://dropbox.nakkaya.com/builds/ferret-manual.html [2] http://nakkaya.com/2011/06/29/ferret-an-experimental-clojure... (Old version for more documentation on the idea.) [3] https://en.wikipedia.org/wiki/Literate_programming

duncanawoods
That doesn't sound hard to me - you just use a high level type that implements the coercion/conversion rules of the dynamic lang types.

GC lang to non-GC lang is a more interesting challenge. If anyone has transpiled a gc lang to C++ I'd love to know how they did it.