Editing Fixed-point combinator (section)

===Example implementations===
An example implementation of ''Y'' in the language [[R (programming language)|R]] is presented below:<syntaxhighlight lang="r">
Y <- \(f) {
  g <- \(x) f(x(x))
  g(g)
}
</syntaxhighlight>This can then be used to implement factorial as follows:<syntaxhighlight lang="r">
fact <- \(f) \(n)
  if (n == 0) 1 else n * f(n - 1)
  
Y(fact)(5) # yields 5! = 120
</syntaxhighlight>Y is only needed when function names are absent. Substituting all the definitions into one line so that function names are not required gives:<syntaxhighlight lang="r">
(\(f) (\(x) f(x(x)))(\(x) f(x(x)))) (\(f) \(n) if (n == 0) 1 else n * f(n - 1)) (5)
</syntaxhighlight>This works because R uses [[lazy evaluation]].

Languages that use [[strict evaluation]], such as [[Python (programming language)|Python]], [[C++]], and other [[strict programming language]]s, can often express Y; however, any implementation is useless in practice since it [[infinite loop|loops indefinitely]] until terminating via a [[stack overflow]].