Re: [boost] Alternative solution to intermediate results problem of expression templates.

From: Korcan Hussein (korcan_h_at_[hidden])
Date: 2005-10-23 09:49:11

"Larry Evans" <cppljevans_at_[hidden]> wrote in message 
news:435B9E00.3030607_at_cox-internet.com...
> On 10/22/2005 06:58 AM, Larry Evans wrote:
> Are you suggesting this as an alternative to Spirit subrules?

Doesn't need to replace subrules but could be an alternative implementation 
for them, if you read the part:

[qoute]
... It might not be apparent but behind the scenes, plain rules are actually 
implemented using a pointer to a runtime polymorphic abstract class that 
holds the dynamic type of the parser assigned to it. When a Spirit 
expression is assigned to a rule, its type is encapsulated in a concrete 
subclass of the abstract class. A virtual parse function delegates the 
parsing to the encapsulated object.
Rules have drawbacks though:

 It is coupled to a specific scanner type. The rule is tied to a specific 
scanner [see The Scanner Business].
 The rule's parse member function has a virtual function call overhead that 
cannot be inlined.

[/quote]

That is what automatic type erasing is, i think there is an alternative to 
this that might be worth investigating if not done so already. I'm just on 
the verge of finishing make my (simple, primitive) example tidy, should be 
up in a thew hours.

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