On 1/6/11 4:29 PM, Stewart Gordon wrote:
On 02/01/2011 13:01, Manfred_Nowak wrote:
Walter Bright wrote:
writing generic code so that the same code can be generated for void
and non-void return values.
http://d.puremagic.com/issues/show_bug.cgi?id=5399 (cited 01/02/11)
The docs include:
| Expressions that have no effect, like (x + x), are illegal in
| expression statements. If such an expression is needed, casting it to
| void will make it legal.
http://www.digitalmars.com/d/2.0/statement.html#ExpressionStatement
| If the Expression has no side effects, and the return type is void,
| then it is illegal.
http://www.digitalmars.com/d/2.0/statement.html#ReturnStatement
( both cited 01/02/11)
Walters remark suggests that the dysmorphism between returnStatement and
expressionStatement is based on arbitrariness: generating an expression
by generic code must still take into account, whether the genrated
expression will be used for an expressionStatement or a returnStatement.
This is because casting to void will not legalize an expression without
side effects for a returnStatement, but for an expressionStatement only.
Then why not fix ReturnStatement so that
return cast(void) Expression ;
is always legal in a void-returning function?
Perhaps the way to do it is to define that the semantic analyser always
deems cast(void) Expression to have a side effect.
To make this homomorphic it might be adequate to view returning as an
attribute of an expressionStatement:
`(void).return;' instead of `return;' whithin `void f(){}'
`(1).return;' instead of `return 1;' whithin `int f(){}'
<snip>
I don't really like this - it seems unnatural. return is a control flow
statement. Properties of objects, by their nature, don't control the
flow of the calling function (throwing exceptions aside).
Stewart.
Guys, this is getting really bizarre. We now have syntax proposals for
fixing... what problem? Walter, please drop that feature and let's move
on. Again, you can take my word that such a feature offers nothing to
generic and generative programming.
Andrei
