Patter.Net 1.0.1

Patter.net

A simple pattern matching library for fluently extracting data from text.

Rationale

I frequently find myself trying to pull a bit of structured data out of a stream of text. Regex is an amazingly powerful tool, but I have always struggled to get it to return structured results, and frequently just write my own little parser to extract the information I want. Patter is a simple library to describe seeking and grabbing the chunks of data you want without the complexity of Regex.

• Is it more powerful than Regex? Absolutely not, if Regex is your jam, use Regex.
• Is it easier to read and get data out? IMHO yes.

Extracting text

You can use Patter<string> to extract text.

For example:

var pattern = new Patter<string>()
    .SeekPast("<foo>")
    .CaptureUntil("</foo>");

var results = pattern.Matches("Show <foo>one</foo> and <foo>two</foo>");

returns

["one","two"]

Extracting complex objects

Let's say you want to extract anchors from a blob of text. You want just the href and the link text.

To do that you define the result object:

public class ALink
{
   public string Text {get;set;}
   public Uri Url {get;set;}
}

And then define a pattern using Patter<ALink>:

    // define a patter to return enumeration of ALink objects.
    var pat = new Patter<ALink>()
        // seek to <a 
        .Seek("<a") 
        // seek past href attribute
        .SeekPast("href=") 
        // skip quotes if there any 
        .SkipChars(Chars.Quotes) 
        // Capture everything up to closing tag or end quote, and convert it a Uri and store in Alink.Url
        .CaptureUntilChars(">'\"", (context) => context.Match.Url = new Uri(context.MatchText))
        // skip quotes if there any 
        .SkipChars(Chars.Quotes)
        // seek past end of opening tag
        .SeekPast(">") 
        // capture everything up to the close </a tag and put it into the Alink.Text 
        .CaptureUntil("</a", (context) => context.Match.Text = context.MatchText.Trim()); 

    var matches = pat.Matches("this is a <a href=\"http://foo.com\">link1</a> <a href=http://bar.com>link2</a>").ToList();
    Debug.WriteLine(JsonConvert.SeriializeObject(matches));

This will extract the text and urls from the tags. It's an enumerable, so you can use LINQ statements to further manipulate the results.

[
    { 
          "Text":"link1"
          "Url":"http://foo.com"
    },
    { 
          "Text":"link2"
          "Url":"http://bar.com"
    }
]

Methods

PatternContext

The pattern context represents the current state of parser. It has the following properties of interest

Technical notes

Patter patterns are 100% reusable and thread safe (meaning multiple threads can be evaluating a Patter pattern against strings safely).