Reversing a List: Using if

fun rev lst = if lst = nil then nil

else rev(tl(lst))@[hd(lst)];

val rev : fn ''a list -> ''a list

rev [1, 2, 3, 4];

val it = [4, 3, 2, 1] : int list

rev [“nice”, “feature”, “recursion”];

val it = [“recursion”, “feature”, “nice”] : string list

rev [1.0, 2.0, 3.0];

Error: operator and operand don’t agree (equality type required)

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