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A pure Python scannerless LR/GLR parser.

For more information seethe docs.

This is just a small example to get the general idea. This example shows how toparse and evaluate expressions with 5 operations with different priority andassociativity. Evaluation is done using semantic/reduction actions.

The whole expression evaluator is done in under 30 lines of code!

fromparglareimportParser,Grammargrammar=r"""E: E '+' E  {left, 1} | E '-' E  {left, 1} | E '*' E  {left, 2} | E '/' E  {left, 2} | E '^' E  {right, 3} | '(' E ')' | number;terminalsnumber: /\d+(\.\d+)?/;"""actions= {"E": [lambda_,n:n[0]+n[2],lambda_,n:n[0]-n[2],lambda_,n:n[0]*n[2],lambda_,n:n[0]/n[2],lambda_,n:n[0]**n[2],lambda_,n:n[1],lambda_,n:n[0]],"number":lambda_,value:float(value),}g=Grammar.from_string(grammar)parser=Parser(g,debug=True,actions=actions)result=parser.parse("34 + 4.6 / 2 * 4^2^2 + 78")print("Result = ",result)# Output# -- Debugging/tracing output with detailed info about grammar, productions,# -- terminals and nonterminals, DFA states, parsing progress,# -- and at the end of the output:# Result = 700.8

• Stable version:

$ pip install parglare

• Development version:

$ git clone git@github.com:igordejanovic/parglare.git$ pip install -e parglare

If you use parglare in your research please cite this paper:

Igor Dejanović, Parglare: A LR/GLR parser for Python,Science of Computer Programming, issn:0167-6423, p.102734,DOI:10.1016/j.scico.2021.102734, 2021.@article{dejanovic2021b,    author = {Igor Dejanović},    title = {Parglare: A LR/GLR parser for Python},    doi = {10.1016/j.scico.2021.102734},    issn = {0167-6423},    journal = {Science of Computer Programming},    keywords = {parsing, LR, GLR, Python, visualization},    pages = {102734},    url = {https://www.sciencedirect.com/science/article/pii/S0167642321001271},    year = {2021}}

MIT

Tested with 3.6-3.11

Initial layout/content of this package was created withCookiecutter and theaudreyr/cookiecutter-pypackage project template.