Enhanced type guard syntax]

Vlad Dumitrescu <>
Thu Sep 18 16:16:12 CEST 2003


Joe wrote:
>   Adding  guards  like  this   violates  one  of  my  favorite  design
> meta-principles:  " If  you add something  to a language  you have to  chuck
something
> away "
>
>   What are we going to chuck away?  Well not "when ->" ...  Since you can't
say
> foo(X, Y) when X == 2*Y ->
>   in the new syntax
>   So you keep "when" - now there are TWO ways of saying things
> foo(A/integer, B/integer)
>   or
> foo(A, B) when is_integer(A), is_integer(B) ->
>   and people will write:
> foo(A/integer, B) when is_integer(B) ->
>     ...
>   etc.

Why not throw away the "when is_integer()" guards? Let type be only be specified
using the new syntax, and let other kind of guards be specified as before. It
seems to me it should work. What do you think?

Of course, this would break backwards compatibility. Since I'm not at Ericsson
(anymore) I can happily propose to write a tool for automated conversion of code
to the new format. :-)

regards,
Vlad



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