Compiling forward references

Does this look like a worst case?

01 a LIKE b.
01 b LIKE c.
01 c LIKE d.
....
01 y LIKE z.
01 z PIC X.

A simple-minded compiler would take 25 forward sequential scans to resolve a. If the
compiler ran every other scan backwards, definitions would be resolved in two passes, but
that's not a good solution either.

The right solution would put the names a, b, c ... z into a tree or hash table, with a
link to definitions in the source program. Think of it as a dictionary, if that helps.
Then the resolution is not done by multiple sequential passes of the whole source code but
rather by high speed lookups.

Compilers already do that. When they compile MOVE a TO b, do you think they find a and b
by sequentially reading through the source? Of course not.

Given that compilers already have a tool for rapidly finding names, resolving meta
references can be done with recursive invocation of that tool. When a needs the definition
of b, push the context, search for b, receive b's definition, pop context, replace LIKE
phrase with definition.

If the stack overflows, you've got a circular reference.

I don't understand why such a simple problem is causing heartburn.
.

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