Tue Dec 16 11:58:58 CET 2003
> 2. As Dr. Joe (again congratulations Joe) points out "a+42" IS LEGAL ERLANG! Sorry for shouting but the point must be stressed. How can any one seriously suggest that the compiler disallow legal code? You are actually changing the semantics of the language when you do this. Are you aware of this fact?
As I pointed out before there can be two possible reasons why the
programmer wrote a+42.
1) The programmer made an error, or,
2) The programmer wants the system to raise an exception.
THERE IS NO WAY THE COMPILER KNOWS WHICH OF THESES TWO CASES APPLIES
(Sorry for shouting)
You must tell the compiler (ie the compiler needs to know the
programmer's intention - << what I call intentionality >>)
There are two ways of telling the compiler:
a) add pragmas to Erlang
b) add a known wrapper that the compiler understands
for example make a function
this_is_not_an_error(X) -> X. and then call it thus:
this_is_not_an_error( a + 42)
Method b) needs no syntactic changes to the language, and (I guess)
a very simple change to the compiler.
If we adopt b) then the compiler should reasonably behave as follows:
a+42 Produces a warning
and compiles the code correctly
this_is_not_an_error(a+42) Compiles the code correctly
with no warning
In both cases the function is compiled - the only difference is
whether you warn or not.
Robert is entirely right - legal code must ALWAYS be correctly
compiled --- the compiler should never try to outguess the programmer
and guess that this was an error - half our test suits would stop
working if this were the case.
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