An interpreter modeled after a calculator implemented in Python 3. The program currently only supports basic mathematical expressions. The package uses Reverse Polish Notation also known as postfix expression internally to easily represent mathematical expressions. This is powerful as it allows operators to be organised in such a way that precedence is absolute meaning an operator that is encountered first will always be executed first.
However, it is obvious that postfix is not normal or rather not usually taught in schools and thus infix expression is still the way for the user to write expressions. The interpreter uses a modified Shunting-Yard algorithm to produce Abstract Syntax Trees. Evaluation of ASTs is trivial, and they are flexible making it easy to extend the grammar and functionality later on.
The package is available in PyPI and can be installed via pip.
pip install expr-calc
#or
python3 -m pip install expr-calc
The best way to run the program currently is to execute the REPL and can be done in a python file or through your terminal.
Assuming your present working directory is inside the cloned repo, you can run the following command without the comment.
# inside /clone_path/expr_calc/
python -m expr_calc
The test suite can also be ran with pytest when inside the cloned repo
pytest # or python -m pytest
Once inside the REPL, you can start evaluating expressions. Currently, only operators listed in Features are supported.
calc> 1 + 1
2
calc> 345--500
845
calc> -2
-2
calc> 123 ^ 4
228886641
calc> 32 / 1.5
21.33333333333333333333333333
calc> 123 * 456
56088
calc> 34 % 5
4
calc> 4 ^ 1/2
0.5
calc> 4 ^ (1/2)
2.0
+, -, *, /, %, ^sin, cos, tan, etcFAQs
Expression interpreter modeled after a calculator
We found that expr-calc demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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