[erlang-questions] lists:reverse/1 as a built-in function
Fri Jan 12 11:17:07 CET 2007
I think the main problem here is semantic, what is meant by a built-in
BIFs have always meant things that were part of the Erlang language but
didn't have a special syntax; they looked like "normal" function calls.
How they are implemented is completely irrelevant! Spawn, link, size etc
are all just as much a part of the language as ! and receive, but they
have no special syntax, they are BIFs. Both spawn/3 and spawn/4 are
BIFs, spawn/3 is implemented in C while spawn/4 is implemented in
Erlang. The unfinished Erlang standard addresses the use of the term
BIF. Unfortunately the reference manual is not clear on this point.
So with this in mind it is not really strange that BIFs are
auto-imported, and have priority over "normal" functions defined in
modules; they are part of the language. It is perhaps unfortunate that
we allowed definition of functions with the same name and arity as the
What is a bit of a mess is that some BIFs are auto-imported while some
you can only reach by explicitly using the module name erlang. Well all
exist in the module erlang but for some this is implicit. Unfortunately
there seems to be no clear logic why some BIFs are auto-imported and
some need to be prefixed with erlang. This is an old problem.
The meaning of BIF was not really a problem until functions which are
clearly not BIFs were implemented in C for efficiency, functions like
append and reverse. These functions are perfectly logically part of the
What is needed is a new term to describe functions which are implemented
in C in the emulator which are not BIFs.
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