Templates; what does the standard mean here...

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2 total messages Started by David Byrden Thu, 22 Feb 1996 20:22

#3410

Author: David Byrden
Date: Thu, 22 Feb 1996 20:22

36 lines
1792 bytes

From the January draft standard:

1 A template can be referred to by a template-id:
          template-id:
                  template-name < template-argument-list >
          template-name:
                  identifier
          template-argument-list:
                  template-argument
                  template-argument-list , template-argument
          template-argument:
                  assignment-expression
                  type-id
                  template-name


 Notice the third-last line, "assignment-expression". 

 Call me dumb, but I must ask what does this mean? What does the 
expression specify, a type or a value? Will an assignment be made at run 
time?

 Can you give me any examples of templates specialised with an 
assignment-expression?


                         Thankyou.

                                   David
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Re: Templates; what does the standard mean here...

#3436

Author: David Vandevoorde
Date: Sat, 24 Feb 1996 17:15

40 lines
2065 bytes

>>>>> "DB" == David Byrden <100101.2547@compuserve.com> writes:
DB> From the January draft standard:
[...]
DB>           template-argument:
DB>                   assignment-expression
DB>                   type-id
DB>                   template-name


DB>  Notice the third-last line, "assignment-expression". 

Assignment expressions are described in Chapter 5 ([expr.assign] or 
something similar). They're basically your classical expression with
operation precedence downto assignments (e.g., not a comma-expression).

DB>  Call me dumb, but I must ask what does this mean? What does the 
DB> expression specify, a type or a value? Will an assignment be made at run 
DB> time?

This is for non-type template arguments.

This is only the syntax description. In [temp.arg] you should find
that the expression must be a non-floating-type, constant expression
(i.e., one that can easily be determined at compile-time).

DB>  Can you give me any examples of templates specialised with an 
DB> assignment-expression?

	template<bool B> struct PlaceHolder {};

	PlaceHolder<(4<5)> hello_variable;


	Daveed
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