[Tutor] Learning about other languages by using Python [Scheme!]

[Danny Yoo]

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[Skip this message if you're just beginning to learn Python; this post
refers to another language called Scheme, so it might be confusing.]


Hi everyone,

I'm thinking of writing a silly Scheme interpreter in Python; hopefully
I'll be able to get it done before I forget.  *grin*

Scheme is one of the "simple" languages that beginning computer science
students often play with.  It has almost no syntax, which makes it
relatively easy to write a parser for it.

Almost all of Scheme is based on processing lists, so Scheme optimizes its
syntax toward list building.  For example, in Scheme,

    (one two (three) 4)

is equivalent to Python's:

    ['one', 'two', ['three'], 4]


Just in case I get hit by a bus, I'll send off a bit that already (sorta)
works to Useless Python.


###
dyoo@einfall:~/pyscheme$ python schemeparser.py
Type 'quit' to exit this test.

[SchemeParser] >>> (define (square x) (* x x))
['define', ['square', 'x'], ['*', 'x', 'x']]

[SchemeParser] >>> (1 2 3 4 (5 6 (7 8 (9))) 10)
[1, 2, 3, 4, [5, 6, [7, 8, [9]]], 10]

[SchemeParser] >>> this shouldn't work
Uh oh! While trying to eat None: got token ('symbol', 'shouldn') instead.

[SchemeParser] >>> ''''muhahaha
['quote', ['quote', ['quote', ['quote', 'muhahaha']]]]
###


Hope this helps!

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