!standard 4.2.1(15/5)                                    20-10-15  AI12-0403-1/01
!standard 4.2.1(17/5)
!standard 4.2.1(18/5)
!standard 4.2.1(19/5)
!standard 4.3.5(93/5)
!class binding interpretation 20-10-15
!status work item 20-10-15
!status received 20-10-15
!priority Low
!difficulty Easy
!qualifier Omission
!subject Presentation issues from Draft 26 review
!summary

Various presentation issues were noted by reviewers of Draft 26.

!question

(1) In 4.3.5(93/5), "Add_Positional" is not defined; it should
be "Append_One", right? (Yes.)

(2) In 4.2.1(17/5), we have

    function To_Roman_Number (S : String) return Roman_Number

But this function needs to have a parameter of Wide_Wide_String to
meet the requirements on the profile of a String_Literal function,
right? (Yes.)

[Editor's note: More issues to be added here.]

!recommendation

(1) Fix as suggested.

(2) Add "Wide_Wide_" in a number of places, and reformat as needed.

[Editor's note: More issues to be added here.]

!wording

Modify 4.2.1(15/5-20/5):

   subtype Roman_Character is {Wide_Wide_}Character
      with Static_Predicate =>
         Roman_Character in 'I' | 'V' | 'X' | 'L' | 'C' | 'D' | 'M';

   Max_Roman_Number : constant := 3_999;  -- MMMCMXCIX

   type Roman_Number is range 1 .. Max_Roman_Number
      with String_Literal => To_Roman_Number;

   function To_Roman_Number (S : {Wide_Wide_}String) return Roman_Number
      with Pre => S'Length > 0 and then
         (for all Char of S => Char in Roman_Character);

   function To_Roman_Number (S : {Wide_Wide_}String) return Roman_Number is
      (declare
         R : constant array (Integer range <>) of Roman_Number :=
            (for D in S'Range => Roman_Digit'Enum_Rep
                (Roman_Digit'{Wide_Wide_}Value (''' & S(D) & '''))); -- See 3.5.2 and 13.4
       begin
         [for I in R'Range =>
            (if I < R'Last and then R(I) < R(I + 1) then -1 else 1) * R(I)]
               'Reduce("+", 0)
      );

   X : Roman_Number := "III" * "IV" * "XII"; -- 144 (that is, CXLIV)

Modify 4.3.5(93/5):

--  Is equivalent to:
V := Empty_Vector (<estimate of size of M>); for Elem of M loop
   [Add_Positional]{Append_One} (V, Elem); end loop;

!discussion


!ASIS

No ASIS effect.

!ACATS test


!appendix

!topic Wrong profile in 4.2.1 Examples
!reference Ada 202x RM4.2.1(18/5,19/5)
!from Max Reznik 20-09-14
!keywords User-Defined String Literal Wide_Wide_String
!discussion

In ARM 202x Draft 26 "4.2.1 User-Defined Literals" there is an example:

    function To_Roman_Number (S : String) return Roman_Number

But its profile is incorrect, because, according to the rules above,
the parameter should have Wide_Wide_String type.

****************************************************************

!topic Wrong profile in 4.2.1 Examples
!reference Ada 202x RM4.2.1(18/5,19/5)
!from Max Reznik 20-09-14
!keywords User-Defined String Literal Wide_Wide_String !discussion

In ARM 202x Draft 26 "4.2.1 User-Defined Literals" there is an example:

    function To_Roman_Number (S : String) return Roman_Number

But its profile is incorrect, because, according to the rules above, the 
parameter should have Wide_Wide_String type.

****************************************************************

From: Christoph Grein
Sent: Wednesday, September 23, 2020 7:35 AM

There is more wrong:

In (19/5) Reduce("+", 0), zero does not belong to the subtype Roman_Number, 
so it's illegal.

****************************************************************

From: Christoph Grein
Sent: Wednesday, September 23, 2020 7:59 AM

Oh, and also negative numbers are not in range, so also this  is illegal:

(if I < R'Last and then R(I) < R(I + 1) then -1 else 1) * R(I)]

****************************************************************

From: Christoph Grein
Sent: Saturday, October  3, 2020  5:24 AM

Hm, I withdraw my claims about the initial value 0 and factor -1 being 
illegal. value_type and accum_type are Roman_Number'Base, a subtype of the
type of Roman_Number.

****************************************************************

From: Tucker Taft
Sent: Monday, October 5, 2020  9:21 AM

In 4.3.5(93/5), the example should be fixed as follows:

--  Is equivalent to:
V := Empty_Vector (<estimate of size of M>); for Elem of M loop
   [Add_Positional]{Append_One} (V, Elem); end loop;

****************************************************************