Unable to use function call in function guard

Question

I\'m new to Erlang and am trying to program a bounded-buffer problem program. It is almost working, except for making sure the producers don\'t get too far ahead and overwr

Answer 1

As Geoff Reedy has mentioned there are only few BIFS that are allowed in guards.

But the guardian parse transform library can be used to call any function in guards.

Answer 2

There are only certain functions that can be used in a guard, see Guard Sequences in the Erlang manual. You can easily do what you need as follows:

buffer(Buf, NextWrite, NextRead) -> buffer(Buf, NextWrite, NextRead, array:size(Buf)).

buffer(Buf, NextWrite, NextRead, _) when NextWrite == NextRead -> 
  ;
buffer(Buf, NextWrite, NextRead, BufSize) when (NextWrite - NextRead) == BufSize ->
  ;
buffer(Buf, NextWrite, NextRead, _) ->
  .