compiler question ?

Bjorn Gustavsson <>
Wed Oct 11 17:42:49 CEST 2000


 writes:

> is the compiler smart enough to detect that something is unchanged, and then 
> not copy it again ( on stacks, or whatever )
> 
> f(A) ->2* g(A).
> 
> is A copied on the stack, or just passed around ? ( Ais big in my case, and 
> quite deep recursion is happenning)

The Beam compiler only saves variables on the stack if they will actually
be used later in the same function. In your case, A will not be saved on
the stack.

> 
> generally speaking , in FP , are things passed around as values or pointer ?
> 

It depends on the type. In Erlang we use 32 bits words that can contain
either a value (for instance an integer or an atom), or pointer to complex
terms likes list cells or tuples. In both cases there a tag bits that
indicates the type.

/Bjorn
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Björn Gustavsson            Ericsson Utvecklings AB
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