Every number belongs to corresponding prefix (“a”, “ab”, “aba”, …) and for each prefix it represents length of longest suffix of this string that matches prefix. We do not count whole string as suffix or prefix here, it is called self-suffix and self-prefix (at least in Russian, not sure about English terms). So we have … Read more
This is exactly why I wrote these functions, which are apparently impressively obscure since nobody has mentioned them. scala> import PartialFunction._ import PartialFunction._ scala> cond(“abc”) { case “def” => true } res0: Boolean = false scala> condOpt(“abc”) { case x if x.length == 3 => x + x } res1: Option[java.lang.String] = Some(abcabc) scala> condOpt(“abc”) … Read more
See show-paren-mode as described in 5.27 How do I show which parenthesis matches the one I’m looking at?
In a nutshell, patterns are like defining piecewise functions in math. You can specify different function bodies for different arguments using patterns. When you call a function, the appropriate body is chosen by comparing the actual arguments with the various argument patterns. Read A Gentle Introduction to Haskell for more information. Compare: with the equivalent … Read more
{ case X(x) => … } is a partial function, but the compiler still doesn’t know what your input type is, except that it’s a supertype of X. Normally this isn’t a problem because if you’re writing an anonymous function, the type is known from the context. But here is how you can provide the … Read more
Keys is specifically noted as a command not to be run in production due to the way it works. What you need here is to create an index of your keys. Use a set for storing the key names of the pattern you want. When you add a new we key, add the name of … Read more
Believe it or not, this works: val b = List(1, 2) b map { case 1 => “one” case 2 => “two” } You can skip the p => p match in simple cases. So this should work: val c = a map { case ((x,y) -> u) => (y,x) -> u }
So far as I know there’s no way to make it a one-liner in current Python without introducing another function, e.g.: split_list = lambda lst: (lst[0], lst[1:]) head, rest = split_list(my_func()) However, in Python 3.0 the specialized syntax used for variadic argument signatures and argument unpacking will become available for this type of general sequence … Read more
I would start here: http://en.wikipedia.org/wiki/Longest_common_substring_problem There are links to supplemental information in the external links, including Perl implementations of the two algorithms explained in the article. Edited to add: Based on the discussion, I still think Longest Common Substring could be at the heart of this problem. Even in the Journal example you reference in … Read more
They serve very different purposes. Full Text Search is used to return documents that match a search query of stemmed words. Trigrams give you a method for comparing two strings and determining how similar they look. Consider the following examples: SELECT ‘cat’ % ‘cats’; –true The above returns true because ‘cat’ is quite similar to … Read more