Skip to content

930-StringHelpers.md

Latest commit

 

History

History
112 lines (89 loc) · 4.96 KB

930-StringHelpers.md

File metadata and controls

112 lines (89 loc) · 4.96 KB
Raw

QuickData.Core.FSharp

StringHelpers

This module provides various string-based functions which might be useful.

The StringHelpers Module

The StringHelpers module provides functions for working with strings.

These functions are:

  • removeControlCharacters : Returns a string which contains no control characters;
  • removeSpaces : Returns a string which contains no spaces;
  • removeAllButNumerals : Returns a string which contains only numerals;
  • removeAllButLettersAndNumerals : Returns a string which contains only letters and numerals;
  • rev : Returns a string which contains the characters in the original string reversed;
  • capitalise : Returns a string which contains the characters in the original string with the first character converted to upper-case (if it's a letter);
  • joinedWith : Returns a string which contains the strings in the original sequence joined with the joiner string between each source string (some convenience functions are also available);
  • joinedVia : Returns a string which contains the strings in the source sequence with a joiner string between each element;
  • split : Returns an array of string which contains the parts of the original string split at the characters supplied.

Note: These functions require that the StringHelpers module name be prefixed to the function name (just so they don't interfere with other functions with the same name).

Active Patterns

The following active patterns are also available:

  • |StringIsEmpty|StringIsNotEmpty| : Is the string empty or only contains spaces?
  • |StringContainsControlCharacters|StringDoesNotContainControlCharacters| : Does the string contain control characters?
  • |StringOnlyContainsNumbers|StringContainsMoreThanJustNumbers| : Does the string only contain numbers?
  • |StringOnlyContainsLetters|StringContainsMoreThanJustLetters| : Does the string only contain letters (either upper- or lower-case)?
  • |StringStartsWithSpace|StringDoesNotStartWithSpace| : Does the string start with a space?
  • |StringEndsWithSpace|StringDoesNotEndWithSpace| : Does the string end with a space?
  • |StringIsLongerThan|_| : Is the string longer than the specified length?
  • |StringIsShorterThan|_| : Is the string shorter than specified length?

None of these functions/patterns do anything 'fancy' but they can be convenient to use on occasion.

Code Examples

let withNoControlCharacters = 
    "\aNo\n Mess\r" 
    |> StringHelpers.removeControlCharacters // -> "No Mess"

let reversed = "abcd" |> StringHelpers.rev // -> "dcba"

let joined = 
    seq { "same" ; "join" ; "between" ; "strings" }
    |> StringHelpers.joinedWith "-" 
    // -> "same-join-between-strings"

let joinedVia = 
    seq { "different" ; "joiners" ; "between" ; "strings" }
    |> StringHelpers.joinedVia (seq { "-" ; "/" ; "=" })
    // -> "different-joiners/between=strings"

open QuickData.FSharp.StringHelpers 

// Active patterns can be used alone, for example:
let isEmpty = // -> "is empty"
    match "" with 
    | StringIsEmpty -> "is empty"
    | StringIsNotEmpty -> "not empty"

let tooLong = // -> "too long at 14 characters"
    match "my long string" with 
    | StringIsLongerThan 6 length -> "too long at " + length.ToString() + " characters"
    | _ -> "okay length"

//...or they can be used together for basic validation:
let results = 
    [ "" 
      "return\r"
      " starts with space" 
      "ends with space " 
      "too many characters" 
      "short" 
      "   "
      "this is okay"
      "\n\a\r"
      String.Empty ]
    |> List.map (fun str -> 
        match str with 
        | StringIsEmpty -> "string is empty"
        | StringContainsControlCharacters -> "contains control characters"
        | StringStartsWithSpace -> "starts with space"
        | StringEndsWithSpace -> "ends with space"
        | StringIsLongerThan 12 length -> "too long at " + length.ToString() + " characters"
        | StringIsShorterThan 6 length -> "too short at " + length.ToString() + " characters"
        | _ -> str)
    // -> ["string is empty"; "contains control characters"; "starts with space";
    //     "ends with space"; "too long at 19 characters";
    //     "too short at 5 characters"; "string is empty"; "this is okay";
    //     "contains control characters"; "string is empty"]

Issues, Questions, and Suggestions

You can visit the QuickData.FSharp GitHub repository to report issues, ask questions, or make suggestions. You can also read about the changes across different versions in the release notes there.