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I was trying to read docs/core-spec/core-spec.pdf to understand the operational semantics for core language. So I started off by playing with operational semantics rules manually.

But I found the following expression gets stuck:

v1 = let fix = \f -> let x = f x in x
         pf = \f x -> if x == 0
                          then x
                          else f (pred x)
     in (fix pf) 2
-- S_LETNONREC
v2 = ((\f -> let x = f x in x)
      (\f x -> if x == 0
                   then x
                   else f (pred x)))
     2
-- S_APP
v3 = (let x = (\f x -> if x == 0
                           then x
                           else f (pred x)) x
      in x) 2
-- S_APP; S_LETREC
v4 = (let x = (\f x -> if x == 0
                           then x
                           else f (pred x)) x
      in (\f x -> if x == 0
                      then x
                      else f (pred x)) x) 2
-- S_APP
v5 = (let x = (\f x -> if x == 0
                           then x
                           else f (pred x)) x
      in (\x1 -> if x1 == 0
                     then x1
                     else x (pred x1))) 2

at this point x is not a free variable so S_LETRECRETURN cannot be applied.

Did I make it wrong or some rules are missing for the operational semantics?

Trac metadata

Trac field	Value
Version	7.8.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Documentation
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