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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: syntaxic exploration
Date: Sat, 23 Dec 2017 15:04:55 +0200
Organization: Tidorum Ltd
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Xref: reader02.eternal-september.org comp.lang.ada:49607
Date: 2017-12-23T15:04:55+02:00
List-Id: <comp.lang.ada>

On 17-12-23 14:16 , Mehdi Saada wrote:
> As I see it, but I don't know the intricated rules of
> extended return statements, RES seems to be initialized as
> a constrained record object.

I believe it is. Does the DEGRE discriminant have a default value? If 
not, all T_POLYNOME objects are constrained.

> Does "return RES: T_POLYNOME (T_DEGRE'MAX(POLY_A.DEGRE,POLY_B.DEGRE)) do"
> constrains its discrimant ?

Yes, just as a declaration X : String(1..4) constrains the index bounds 
of X.

> It would explain that RES := POLY_REDUIT(RES) three lines below
> causes "raised CONSTRAINT_ERROR : p_poly_v1_g.adb:67 discriminant check failed"

Certainly, if POLY_REDUIT returns a value with a different value of the 
DEGRE discriminant. I guess POLY_REDUIT drops any zero-valued high-order 
coefficients, so it can return a poly with a smaller DEGRE than its input.

I would make RES into a local variable (not an extended return object), 
declare and assign it as now, and then just

    return POLY_REDUIT (RES);

at the end.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .