#MiniScheme#

MiniScheme is a tiny scheme interpreter written in Python 2.7. The interpreter is a single file (scheme.py) and is less than 40 lines of code.

##Usage##

1. Clone the repo:

    git clone [email protected]:cammckinnon/MiniScheme.git
   

2. Navigate to the MiniScheme directory and run the interpreter by typing:

    python scheme.py
   

   It accepts the scheme program as input from standard in and waits for the EOF before interpreting (CTRL-D).

3. Or you can read input from a file like this:

   cat program.ss | python scheme.py

##Features##

• Four standard math functions (+ - / *) are included. They all take an arbitrary number of parameters, except / which only accepts 1 parameter.

• Lambda:

   ((lambda (x)
      (+ 1 x) 1)
   => 2
  

• Equality testing:

   (equal? 1 0) => false
   (equal? 1 1) => true
  

• Conditional branching (with lazy evaluation):

   (if (equal? (2 2)) 1 0) => 1
   (if (equal? (2 3)) 1 0) => 0
  

##Tests##

In the ./tests folder there is a series of tests that check the interpreter for correctness.

    python tests.py

You may find this useful if you wish to modify the interpreter's source code.

##Example##

• Factorial - uses recursion to compute 10! = 3,628,800 .

   ((lambda (factorial)
      (factorial 10 factorial))
     (lambda (i recurse)
       (if (equal? i 1)
         1
         (* i (recurse (- i 1) recurse)))))
  

##Inspiration##

Inspired by http://www.brool.com/index.php/the-tiniest-lisp-in-python .

##What's next?

I will be writing a short tutorial series (likely 3 installments) that will explore the creation of a small scheme interpreter with error-checking, macro support, and a library of built-in functions. Watch http://programmercam.posterous.com/ for updates if you're interested.