Exercise 2: Reproducing the Raw-Slot Local Bug — Possible Solution
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THE REVERT
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    elif instr == OP_GET_LOCAL:
        slot = code[frame.ip]; frame.ip += 1
        self.stack.append(self.stack[slot])       # reverted -- no frame.base

    elif instr == OP_SET_LOCAL:
        slot = code[frame.ip]; frame.ip += 1
        self.stack[slot] = self.stack[-1]          # reverted -- no frame.base

    # program: fun identity(n) { return n; } print identity(42);

RESULT
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    ['<fn identity>']    (correct answer: ['42'])

WHAT'S SITTING AT ABSOLUTE STACK POSITION 0
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Right before identity's own body starts running, the stack (built by
the exact same call convention as every other function call) is:

    stack = [<fn identity>, 42.0]

position 0: <fn identity>   -- the function value itself
position 1: 42.0            -- the one real argument, n

identity's own body compiles `return n;` as OP_GET_LOCAL 0 (n was
declared as the function's first, and only, local -- slot 0). With
the frame.base offset removed, OP_GET_LOCAL 0 reads stack[0]
literally -- which is the FUNCTION OBJECT, not the argument. That
object gets returned, printed, and stringify()'s own WispFunction
branch renders it as "<fn identity>" -- a plausible-looking, entirely
wrong answer, with no error or crash anywhere to flag it.

WHY THIS WORKS AS AN ANSWER
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This confirms the chapter's own central claim precisely: slot
numbers were always meant to be relative to "wherever this
particular call's arguments start," not absolute positions in the
whole stack. Chapter 4 could get away with treating them as the same
thing because the top-level script was the only frame that ever
existed, so its own base was always 0 -- slot number and stack
position happened to be identical by coincidence, not by design. The
instant a second frame exists (which happens on literally the
FIRST function call this course ever compiles, since even calling a
1-argument function pushes the function value at position 0 first),
that coincidence breaks, and "slot 0" stops meaning "absolute
position 0" for any frame except the outermost one.