RosettaCodeData/Task/Anonymous-recursion/Phix/anonymous-recursion-2.phix

function erm(integer n, f)
    return f(n,f)
end function

function fib(integer n)
    if n<0 then throw("constraint error") end if
    return erm(n,function(integer n,f) return iff(n<2?n:f(n-1,f)+f(n-2,f)) end function)
end function

?fib(10)