calvin-l / minilang Goto Github PK

========================= MINI LANG =========================

---- Description

This is an implementation of a tiny turing-complete language.
The language has 3 constructs:

1. set a variable to zero

   x = 0

2. increment a variable

   x+

3. repeat for a specified number of times

   x { ... }

   (NOTE: if you increment x inside the loop, the number of
   iterations increases accordingly, thus allowing for
   infinite loops. Interestingly, changing this rule makes
   the language stop being turing complete.)

---- Additions

The interpreter (minii) also supports a few "syntactic sugar"
additions:

1. set a variable to an arbitrary integer

   x = 402311

   This is equivalent to saying "x = 0" and then incrementing
   x 402311 times.

2. defining functions

   def add(a, b) -> sum = {
       sum = 0
       a { sum+ }
       b { sum+ }
   }
   x = add(45, 29)

   The syntax is a little odd, but just means "this is a
   function that takes 'a' and 'b' and writes its result
   into 'sum.'"

3. builtin functions

   Since this language is very limited, implementations of
   even basic functions can be very slow. For that reason,
   rhe interpreter has builtin implementations of some
   other functions:
      - sub(a,b)           subtraction    (a-b)
      - div(a,b)           division       (a/b)
      - add(a,b)           addition       (a+b)
      - times(a,b)         multiplication (a*b)
      - pow(a,b)           exponentiation (a^b)
      - numFactors(a,b)    number of times b evenly divides a

   If you don't believe such a simple language could
   implement these on its own, check out the examples!

4. print functionality

   x = 12
   print(add(x, 45))

   A language without I/O is pretty boring. Minilang supports
   printing, and it shouldn't be too hard to hack in reading
   later as well.

---- Building

Minii can be built with GNU Make. You will need

 - GHC
 - Alex (http://www.haskell.org/alex/)
 - Happy (http://www.haskell.org/happy/)

Just type "make" to build.

---- Running

Minii takes input on stdin. For instance:

   $ ./minii < examples/cons.mini

---- Examples

There is one demo in the "examples" folder that builds
up to cons cells, implementing successor, subtraction,
division, and some other functions along the way.