GoScheme
The purpose of this project is simply to show that I can do something
of substance in Go. The "something of substance" is to implement an
interpreter for a simple purely applicative subset of the Scheme
programming language.
The program reads a single S-expression from standard input, evaluates
it, and prints the result on standard output.
Since the dialect is purely applicative, the order of evaluation of
the arguments of a function doesn't matter. That means they can be
evaluated in parallel. To make the point, running the program with
the -p option causes the arguments of every function call to be
evaluated in parallel using goroutines. This also makes the point
that I understand something about goroutines and channels. It's
actually more of a loss than a gain for performance since a very large
number of goroutines are created for a deeply recursive function call.
There are four sample Scheme programs:
flatten.txt flattens a nested list.
slowfib.txt computes the 30th Fibonacci number in a slow way.
fastfib.txt computes the 30th Fibonacci number in a fast way.
twice.txt is a contrived example illustrating that the interpreter
correcly handles upward and downward funargs. It should appeal
to Python programmers because it involves spam and eggs.
If this program amuses you, you could consider a couple of enhancement.
1) Make and and or short-circuiting.
2) Modify the program so that it can read dotted pairs like (A.B) or (A B.C)
It will currently print dotted pairs but not read them.
3) Implement cond. cond provides a syntax that replaces chains of nested ifs.
4) Implement let. let provides a way to define variables.
More information about Scheme can be found here:
http://groups.csail.mit.edu/mac/projects/scheme/
(In particular cond and let are defined in the Revised Report on the
Algorithmic Language Scheme.)
This program was my first Go program and required roughly one day's
work. You are free to use it in any way you wish that is consistent
with academic integrity. That's a fancy way of saying that you won't
turn it in for credit in a class.
Rex Dwyer
12 June 2015