Editing Conditional (computer programming) (section)

====Haskell====
{{Main|Haskell (programming language)}}

In [[Haskell (programming language)|Haskell]] 98, there is only an ''if expression'', no ''if statement'', and the <code>else</code> part is compulsory, as every expression must have some value.<ref name="haskell98report">''[http://www.haskell.org/onlinereport/ Haskell 98 Language and Libraries: The Revised Report]''</ref> Logic that would be expressed with conditionals in other languages is usually expressed with [[pattern matching]] in recursive functions.

Because Haskell is [[lazy evaluation|lazy]], it is possible to write control structures, such as ''if'', as ordinary expressions; the lazy evaluation means that an ''if function'' can evaluate only the condition and proper branch (where a strict language would evaluate all three). It can be written like this:<ref name="haskell-ifthenelse-proposal">"[http://haskell.org/haskellwiki/If-then-else If-then-else Proposal on HaskellWiki]"</ref>
<syntaxhighlight lang="haskell">
if' :: Bool -> a -> a -> a
if' True x _ = x
if' False _ y = y
</syntaxhighlight>