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<H2>3 Problem Example</H2>
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<H3>3.1 Description</H3>
<P>A common interoperability situation is when there exists a piece of code solving some complex problem, and we would like to incorporate this piece of code in our Erlang program. Suppose for example we have the following C functions that we would like to be able to call from Erlang.
<PRE>
/* complex.c */
int foo(int x) {
return x+1;
}
int bar(int y) {
return y*2;
}
</PRE>
<P>(For the sake of keeping the example as simple as possible, the functions are not very complicated in this case).
<P>Preferably we would like to able to call <CODE>foo</CODE> and <CODE>bar</CODE> without having to bother about them actually being C functions.
<PRE>
% Erlang code
...
Res = complex:foo(X),
...
</PRE>
<P>The communication with C is hidden in the implementation of <CODE>complex.erl</CODE>. In the following chapters it is shown how this module can be implemented using the different interoperability mechanisms.<CENTER>
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