Hi All,

Here is the code on sorting any given list:

let rec sort lst =
   match lst with
     [] -> []
   | head :: tail -> insert head (sort tail)
 and insert elt lst =
   match lst with
     [] -> [elt]
   | head :: tail -> if elt <= head then elt :: lst else head :: insert elt tail;;

[Source: Code

However, I am getting an Unbound error:

Unbound value tail
# let rec sort lst =
   match lst with
     [] -> []
   | head :: tail -> insert head (sort tail)
 and insert elt lst =
   match lst with
     [] -> [elt]
   | head :: tail -> if elt <= head then elt :: lst else head :: insert elt tail;;
Characters 28-29:
     | head :: tail -> if elt <= head then elt :: lst else head :: insert elt tail;;
     ^
Error: Syntax error

Can anyone please help me understand the issue here?? I did not find head or tail to be predefined anywhere nor in the code