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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Basics : many way to use a Procedure
Date: Sat, 12 Dec 2015 15:33:35 -0700
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On 12/12/2015 03:15 PM, comicfanzine@gmail.com wrote:
>>> In what way does the 4th example,
>>>
>>>   Print_Header(128, Header => Title, Center => True);
>>>
>>> not match those forms?
>>>
>>> Perhaps you'd better post an example of what you think the ARM's syntax
>>> is telling you to write.
>  
>  the 4th example look a little like =
>  
>      [formal_parameter_selector_name =>] explicit_actual_parameter
>  
>  but, there is no "[]" in the 4th example .
>  
>  Also the 4th example doesn't look like this other form , there is no "{}" =
>  
>   actual_parameter_part ::= 
>      (parameter_association {, parameter_association})
> 
> Also , what this next form means ? What means the delimiter " | " ?
> 
> explicit_actual_parameter ::= expression | variable_name

The BNF used to define the syntax is given in ARM 1.1.4.

http://www.adaic.org/resources/add_content/standards/12rm/html/RM-1-1-4.html

You need to be familiar with the notation before you read the rest of the ARM.

Brackets [] surround optional items; braces {} surround items that may appear
zero or more times; the vertical bar | separates alternatives. So

[formal_parameter_selector_name =>] explicit_actual_parameter

means "formal_parameter_selector_name =>" is optional; the parameter 128 in the
example has that part omitted.

actual_parameter_part ::=
   (parameter_association {, parameter_association})

means there's at least 1 parameter_association in an actual_parameter_part, and
if there are more than 1, the others are all preceded by a comma,

explicit_actual_parameter ::= expression | variable_name

means an explicit_actual_parameter is either an expression or a variable_name.

-- 
Jeff Carter
"English bed-wetting types."
Monty Python & the Holy Grail
15