# Tagged Questions

Analyzing (un)structured data to convert it into a structured, normalized format.

557 views

### Idea of an algorithm to detect a website's navigation structure?

Currently I am in the process of developing an importer of any existing, arbitrary (static) HTML website into the upcoming release of our CMS. While the downloading the files is solved successfully, ...
240 views

### “Hand written” recursive descent parser with “catch all” rule

I'm trying to write a (scannerless) recursive descent parser with a "catch all" rule for the following "Mustache template" grammar (simplified here): content : (variable_tag | section_tag | ...
224 views

### content fingerprint algorithm

I have a database containing just simple URLs. It is as simple as it sounds for now and URL can link to a website or a document(i.e. anything parseable to text). Now I have a simple code which ...
391 views

### Practical reference for learning about graph reduction

Are there any practical references (with actual examples) for getting started implementing a small, lazy functional programming language with graph reduction? A reference that included the lexing and ...
297 views

### Best way to parse optional grammar rules?

I started to write a hand written parser just for fun. For simple rules it is working, but I have problem with the optional grammar rules. I marked the optional rules with a question mark. Here is a ...
178 views

### Incorporating functions into a Shunting-Yard algorithm implementation

tl;dr What would be a simple way of incorporating functions into a Shunting-Yard algorithm implementation? If only expressions like function(arg1, arg2, arg3) were allowed (where function is some ...
150 views

### Algorithm to go from infix notation to a tree

I've been trying to figure out an algorithm to go from an infix equation to a syntax tree, like so: (1+3)*4+5 + * 5 + 4 1 3 However, I don't just want it to handle operators, I ...
183 views

### Writing a parser on top of an XML-based AST: am i doing it right?

I have a sort of AST defined in XML that i'm trying to parse and evaluate. The XML tree contains the tokens and all the information i need. However, i'm finding it difficult to do it "properly". Here'...
727 views

### Traversing an AST using Visitors

I'm writing a compiler for a C-like language, and I'm looking for an elegant way to traverse my abstract syntax tree. I'm trying to implement the Visitor pattern, although I'm not convinced that I'm ...
629 views

### How to choose a proper parser generator for PHP

Some programmers avoid regexes in some situations (see this popular @nickf comment), perhaps using a parsing framework such as Lex/Yacc. Others prefer to stay within PHP, perhaps using regular ...
5k views

### Fastest C++ XML parsing library

I have thousands of .xml files from size 1MB-45MB (no DTDs). I need to parse and further manipulate these XML files before generating separate .xml files with the results of my regex. What the ...
148 views

### Clean Abstract Syntax Tree

I'm writing a toy compiler for fun. Basically, my problem is that I don't want to clutter the AST with stuff like debug information (symbol tokens, locations of tokens, etc) as well as data that the ...
418 views

### Building a string parser for user command and control?

My goal is to build a command parser that has basic syntax and multiple possible branches at each point. These commands come from users of the system and are text input (no GUI). The basic syntax is ...
213 views

### Mapping different XML and CSV feeds

Not sure if this is the right venue to be asking this but here goes. A little background. I'm trying to build an ecommerce app that would allow sellers from other venues--like, amazon and newegg--to ...
70 views

### Truncating HTML content at specific content blocks

I have HTML content in my DB and I would like to present a list of these individual items but truncate each of them so they're not fully displayed. I would like to keep truncated items human-...
50 views

### Argument over performance using Convert.ChangeType in Web Applications [duplicate]

A debate has been going on at work about using Convert.ChangeType. A couple of fundamental assumptions to this discussion are delineated below: 1. The discussion is within the context of web ...
70 views

### Loop Unfolding and Named Significant Bits

I've been writing a Parser Compiler for the last seven or so years, and I recently got to the point (yet again, never satisfied) of structuring the portion dealing with the portions of the language ...
511 views

### How and when should I design a simple mark-up language parser? [closed]

I want to write a simple markup language with its rendering engine. First, I am not completely sure when I should try this... I am only 12... But I am competent in C++ having learned through the Web ...
209 views

### Implementing semantic actions in table driven predictive parsing

When doing table driven predictive parsing on an LL(1) grammar, (as explained in good detail here for example), how can we augment the algorithm to allow processing of semantic actions while doing the ...
1k views

### I need to develop a parser. Can I use Lex and Yacc for the purpose?

I need to extract very particular data from log files(of different types and formats). Since I am a recent college passout; my mind ran to using Lex and Yacc for the purpose. Now I have the following ...
292 views

### Do markup languages ​​have the equivalent concept of `semantics` that you can find in C or C++?

Maybe I miss something, but do the so called markup languages have the equivalent concept of semantics that you can find in C or C++? Judging from how you parse the language, you don't really have ...
618 views

### Why Double.parseDouble(“ABC”) not returns Double.NaN?

This code: Double.parseDouble("ABC") throws a NumberFormatException. Why is it wrong to expect a Double.NaN (NaN is literally Not-A-Number). A working example is this: public static void main(...
261 views

### Parser and interpreter knowledge as a way to gauge programmer ability [closed]

This is only anecdotal evidence but from my past encounters with programmers at various workplaces the programmers that understand the fundamentals of parsing and interpreting seem to be overall ...
211 views

### Grammar: start: (a b)? a c; Input: a d. Which error correct at position 2? 1. expected “b”, “c”. OR expected “c”

I am writing a parser (a parser generator for PEGs) and am trying to figure out how to report errors. Grammar: rule: (a b)? a c ; Input: a d Question: Which error message correct at position 2 ...
131 views

### Language/Programming term for paired delimiters [closed]

Can someone help me find the language and/or programming term for delimiters (?) that must be paired? Quotes, parenthesis, angle-brackets, square-brackets, etc. are often used to symbolize these ...
164 views

### Is it bad to implement a language in other two languages? [closed]

Ok, so I have some understanding about parsers and compilers, at least the basics of how it works, and i've written a calculator and a really small toy language that compiles to another high-level ...
90 views

### Passing context around AST nodes

I have various objects inside my AST, such as IfBlock, FunctionBlock, LogicExpression, etc. All of those objects share a context, which is basically a hashmap with some variables. It's a very simple ...
663 views

### Is it possible to create a single tokenizer to parse this?

This extends off this other Q&A thread, but is going into details that are out of scope from the original question. I am generating a parser that is to parse a context-sensitive grammar which can ...
1k views

### How to create a Semantic Network like wordnet based on Wikipedia?

I am an undergraduate student and I have to create a Semantic Network based on Wikipedia. This Semantic Network would be similar to Wordnet(except for it is based on Wikipedia and is concerned with "...
128 views

### Is recursive-descent parsing a panacea for DoS threats posed by 'Evil' regexes? Or does evilness stem from the grammar?

ReDos attacks exploit characteristics of some (otherwise useful) regular expressions ... essentially causing an explosion of possible paths through the graph defined by the NFA. So does using a ...
418 views

### High-level strategy for distinguishing a regular string from invalid JSON (ie. JSON-like string detection)

Disclaimer On Absence of Code: I have no code to post because I haven't started writing; was looking for more theoretical guidance as I doubt I'll have trouble coding it but am pretty befuddled on ...
371 views

### Haskell: Best tools to validate textual input?

In Haskell, there are a few different options to "parsing text". I know of Alex & Happy, Parsec and Attoparsec. Probably some others. I'd like to put together a library where the user can input ...
2k views

### Why nginx's http parser doesnt use regular expressions?

I see the http parser written by Igor Sysoev for nginx does not use regular expressions https://github.com/joyent/http-parser What could be the main reason for such design decision? I guess I could ...
35 views

### An elegant way to split text into words combined with adjacent punctuation and determine which punctuation mark it is

Firstly, I realize that question title is about as terrible as the sample code I'll post below, so please bear with me while I explain the problem more clearly, and if you have a better idea for the ...
185 views

### OOP: how to keep some state for a brief moment?

My job and my personal interests often have me writing parsing code, that is, code that converts from an input string written in a given formal language to a tree of model objects. I come from a C ...
124 views

### File validation rules

I have an application that can accept CSV files to run some operations. The files look like: CREATE USER:username,last_name,first_name,age user1,Smith,John,23 user2,Poppins,Mary,257 There are a ...
97 views

### Run a c++ program under lots of different data maps

I want to run a c++ program to process a lot of data from different xml files and output results. I run the program once per file and potentially have around 50 different files. The trouble is each ...
1k views

### Parsing mathematical expressions with two values that have parentheses and minus signs

I'm trying to parse equations like the ones below, which only have two values or the square root of a certain value, from a text file: 100+100 -100-100 -(100)+(-100) sqrt(100) by the minus signs,...
533 views

### PHP Simplest XML tokenizer for string processing?

I need to do some text processing tasks with short XML fragments. The section "details" shows an example... My solution is to use a tokenizer based on regular expresions, but it is not elegant and not ...
495 views

### Should I use a formal grammar for my interpreted scripting language

I have a scripting engine I just published as an open source project. It's been sitting on my harddrive waiting for about a year. My engine of course isn't complete in any way, but it does work for ...
208 views

### How are line/column position data dealt with in parser combinator libraries?

I'm building a parser using a parser combinator library. I need to keep track of where AST nodes started and ended in the textual input -- line and column numbers. How is this problem approached and/...
159 views

### “Fuzzy” parsing in different languages

I have a bunch of plain-text like this: 1 MILE, PACE, PURSE \$1,100. FILLIES & MARES N/W \$541 L5 STARTS AE N/A \$301 L5 & N/A \$60 PS IN 2015-16 DRAW INSIDE ...
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### How to handle user created expressions in application

In our application users can enter custom expressions to calculate certain things. For instance they can specify an invoice and define a number of lines for cost calculation. Example for a course ...
198 views

### Declarative parser for JSON and DOM

I am parsing many JSONs and DOMs in PHP. The problem is that the my knowledge about the structure of the JSON/DOM is mixed with code. For example, suppose that I have few sources of first and last ...
435 views

### How should I handle the fetching of cached data in iOS

I'm developing an app at work, this is my first big application and in my smaller projects I didn't use caching at all. What's currently happening When the user logs on for their very first time ...
57 views

### Can table of content be parsed using some formal grammar?

A table of content can look like: Preface Table of Content Chapter 1 ... 1.1 ... 1.1.1 ... 1.1.2 .... 1.2 ... Summary Exercises Chapter 2 ... ... Appendix ... A ... A.1 ... A.2 ... B ... References ...
491 views

### About AST construction in LL1 non recursive parser

I have implemented a LL1 parser in a non recursive approach with a explicit stack. The following algorithm is from the Dragon Book: set zp to point to the first symbol of w; set X to the top stack ...
294 views

### How would my custom language be categorized?

I'm developing my own scripting language to solve some unique challenges for a project. The language takes source code and converts the contents into tokens, and then a command factory is used to ...