kauboy26/pyevaluator

Evaluates function definitions and assignment statements. If a rock is a planet, this is a language. On this one, I'm building the lexer and parser by hand, in Python.

PyEvaluator

I would like to call this a language, although maybe that's an exaggeration. PyEvaluator evaluates statements that are arithmetic expressions, variable assignments, or function definitions. Here are its features:

• Assignment statement processing
  >> a = 3 + 4
• Multi character variable names
  >> hello = hello + world + 15
• Pre-defined functions (you can call sin(x), etc)
  >> sin(22/7)
• Finally, defining and using your own functions.
  >> def cos(x) = pow(1 - pow(sin(x), 2), 1/2)

Usage

You need Python 2.7 on your computer. Run the following, within the directory containing lex_test_script.py:

python lex_test_script.py

That should start it and you will see a prompt >>. Type in whatever expressions you want, like ">> a0 = 1 + 3 * 4", etc and have a blast. Type in "help" if you don't know what to do.

Oddities

These work:

• >> 3 4 +
  In general, you can misplace arguments, put commas in the wrong place (it depends), etc. In this implementation, only the number of arguments is verified(counting the args and then counting the commas), not the exact position of the arguments. I will fix this later if time permits.

Running Tests

Run this command:
python lex_tests.py
All tests should pass. Ignore the other messages that are printed to console, they are messages from the parser.

pyevaluator's Issues

unary minus not working properly in function definitions

unary minus ins't working all the time in function definitions. This is a replica of the other issue that was opened and resolved earlier, and the fix is nearly the same. Just need to get time to go a fix it.

incorrect behaviour

def g() = 2
def h() = 3

-g() * -h()

Doesn't perform as expected, throws an error instead.