I am working with a file format the contains 32 bit integers.
I need to use int32 on 32 bit systems. I would like to use plain
integers, unboxed and with native machine operations, on 64 bit
systems.
Is there any way to convince ocamlopt to choose between int and
int32 representations _at compile time_?
I could use first class modules to select implementations at
runtime, which is not worth the code complexity and still
requires an indirect function call to add numbers. I could
conditionally compile different files depending on word size,
which strikes me as an ugly and fragile solution.
I want to be able to write "int32" and have that be compiled
like an ordinary integer type if 32 bits and tag fit into a
word, and as a boxed type otherwise. (The compiler could
mask off excess precision if desired.) Is there a reason ocaml
can't provide this?
Another implementation would have each instance of an int32 or
int64 be boxed or not depending on whether the value fits into
a word. I don't know whether this would be faster or slower in
practice. There is a tradeoff between allocations and
conditional branches.
--John Carr ([email protected])
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