Elm Text-Search

Text.Search and Text.Parse provide functions for searching lists of strings or lists of data endowed with a function f: a -> String. Queries are strings which look like foo, -foo, foo bar, foo -bar, foo | bar, etc. A query with foo will match strings containing foo while a query with -foo will match strings not containing foo. A search with foo bar is a conjunctive search: it returns strings containing both foo and bar. Naturally enough, a search with foo -bar returns strings containing foo but not bar. Finally, foo | bar provides for disjunctive searches: strings containing foo or bar will be returned.

Any query in so-called disjunctive normal form is accepted. Such a query is a disjunction of elementary conjunctions, that is, conjunctions of basic terms such as WORD and -WORD.

Example

Running

Search.withQueryString 
   identity 
   Search.NotCaseSensitive 
   "foo -bar | baz"

on the list

[ "foo yada", "foo bar", "hehe, baza baza!" ]

returns the list

[ "foo yada", "hehe, baza baza!" ]

Parse errors

It can happen that the query string is ill-formed, e.g., foo && bar. The functions matchWithQueryStringToResult and withQueryStringToResult return Result String Bool and Result String (List a), respectively and can be used to take action when the query string is ill-formed. At the moment the error message is primitive: "ill-formed query" in all cases.

The companion functions matchWithQueryString and withQueryString are easy to use but simply return False and the empty list, respectively, when the query string is ill-formed.

Spaces

Search terms with spaces are allowed: just surround the term with single quotes. The term 'foo bar' will match "foo bar" but neither "bar foo" nor "foo baz bar".

Non-string data

Suppose that you want to query data of type List a. You can do this if you have function like digest : a -> String. For example, if

type alias Datum = 
  {   title: String
    , tags : List String
    , ... other stuff ... 
   }          

Then

digest datum = String.join " " title::tags

does the job — you can search using

Search.withQueryString 
   digest 
   Search.NotCaseSensitive 
   "foo -bar | baz"