How to write regular expression for a DFA In any automata, the purpose of state is like memory element. A state stores some information in automate like ON-OFF fan switch. A Deterministic-Finite-Automata(DFA) called finite automata because finite amount of memory present in the form of states. For any Regular Language(RL) a DFA is always possible. … Read more
Yes, it turns out this does exist; what is required is what is known academically as a DFA Learning algorithm, examples of which include: Angluin’s L* L* (adding counter-examples to columns) Kearns / Vazirani Rivest / Schapire NL* Regular positive negative inference (RPNI) DeLeTe2 Biermann & Feldman’s algorithm Biermann & Feldman’s algorithm (using SAT-solving) Source … Read more
We can use Stanford Parser from NLTK. Requirements You need to download two things from their website: The Stanford CoreNLP parser. Language model for your desired language (e.g. english language model) Warning! Make sure that your language model version matches your Stanford CoreNLP parser version! The current CoreNLP version as of May 22, 2018 is … Read more
If your focus is generating messages for users of your grammar, see Generating Good Parse Errors from a Parser and Grammar::ErrorReporting. The rest of this answer is about development and debugging of grammars. May 2020 update The obvious choice now is to use the Grammar Live View feature of the Comma IDE. First, you can … Read more
I’m not an expert on the commas, but I know that standard Pascal was very persnickity about semi-colons being statement separators, not terminators. That meant you had to be very very careful about where you put one if you didn’t want to get yelled at by the compiler. Later Pascal-esque languages (C, Modula-2, Ada, etc.) … Read more
You can take a look at pyStatParser, a simple python statistical parser that returns NLTK parse Trees. It comes with public treebanks and it generates the grammar model only the first time you instantiate a Parser object (in about 8 seconds). It uses a CKY algorithm and it parses average length sentences (like the one … Read more
How to write CFG with example ambn L = {am bn | m >= n}. Language description: am bn consist of a followed by b where number of a are equal or more then number of b. some example strings: {^, a, aa, aab, aabb, aaaab, ab……} So there is always one a for one … Read more
There are various Web Services providing automated proofreading and grammar checking. Some have a Python library to simplify querying. As far as I can tell, most of those tools (certainly After the Deadline and LanguageTool) are rule based. The checked text is compared with a large set of rules describing common errors. If a rule … Read more
Constructing an equivalent Regular Grammar from a Regular Expression First, I start with some simple rules to construct Regular Grammar(RG) from Regular Expression(RE). I am writing rules for Right Linear Grammar (leaving as an exercise to write similar rules for Left Linear Grammar) NOTE: Capital letters are used for variables, and small for terminals in … Read more
It makes it easier to generate source code, and also to write code which can be easily extended at a later date. Consider what’s required to add an extra entry to: int a[] = { 1, 2, 3 }; … you have to add the comma to the existing line and add a new line. … Read more