I'm just curious if there are any programming languages that use the '=>' and '=<' operators for something.

I wonder why these are not commonly used when their variant '<=' and '>=' are so widely used by most languages.

Is there a reason why?

EDIT: I'm not asking why they aren't used for the same task as '<=', but why the operators go unused for anything.

  • 5
    My guess is that it is because you say "less or equal than" in English, so it is more natural to write the corrisponding symbols on the keyboard. Aug 20 '13 at 13:07
  • because that would be confusing, it is easier to have only 1 variant than have to do a coinflip each time you need one Aug 20 '13 at 13:08
  • 2
    I use => all the time when doing .net stuff... but I do not think it means what you think it means Aug 20 '13 at 13:10
  • 3
    @DrakeClarris that's inconceivable.
    – Reactgular
    Aug 20 '13 at 13:17
  • 1
    Haskell uses => for type class constraints. Though that's probably not an "operator" ;)
    – Andres F.
    Aug 20 '13 at 13:24

About =>

C# does. Look here: http://msdn.microsoft.com/en-us/library/bb311046.aspx

As MichaelT commented, it is used as a Fat comma. From Wikipedia:

It is primarily associated with PHP, Ruby and Perl programming languages, which use it to declare hashes. Using a fat comma to bind key-value pairs in a hash, instead of using a comma, is considered an example of good idiomatic Perl. In CoffeeScript, the fat comma is used to declare a function that is bound to this.

PHP: http://php.net/manual/en/language.types.array.php

Rails: https://stackoverflow.com/questions/969900/ruby-on-rails-what-does-the-symbol-mean

About =<

Prolog uses it as a comparison operator http://www.cse.unsw.edu.au/~billw/prologdict.html#comparison

  • @MathewFoscarini both symbols are used in programming languages. Take a look at my modified answer. Aug 20 '13 at 13:23
  • 1
    The php and ruby use of => likely comes from the perl fat comma
    – user40980
    Aug 20 '13 at 13:55
  • @MichaelT thank you! I have modified my answer adding infos about fat comma. Aug 20 '13 at 14:35

C# (and others) use => as a function declaration token.

The alternatives are used because when spoken it's always "Less than or Equal to" or "Greater than or Equal to" not "Equal to or...".

  • oh right, ()=>{....} it's hard to remember that when you look just as the operator =>
    – Reactgular
    Aug 20 '13 at 13:11
  • and after C#, coffeescript, and then ES6/Harmony had picked fat arrow syntax.
    – c69
    Aug 20 '13 at 19:45

Scala and ML use => in pattern matching.

Scala Example :

x match {
  case 1 => "one"
  case 2 => "two"
  case _ => "many"

ML Example:

case shape
of Circle (_, r) => 3.14 * r * r
 | Square (_, s) => s * s
 | Triangle (a, b, c) => heron (a, b, c)

Haskell uses it for class constraints :

(Eq a) => a -> a -> Bool  -- type a should be a member of the Eq typeclass

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