From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	ip-172-31-74-118.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=-2.9 required=3.0 tests=BAYES_00,NICE_REPLY_A
	autolearn=ham autolearn_force=no version=3.4.6
Path: eternal-september.org!reader02.eternal-september.org!news.mixmin.net!news2.arglkargh.de!news.karotte.org!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Gnat bug or mistaken program?
Date: Tue, 20 Jul 2021 17:09:08 +0300
Organization: Tidorum Ltd
Message-ID: <ilo3o4F5297U1@mid.individual.net>
References: <318e5e93-5f66-4bb8-8bf0-7ee3fd2688fan@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Trace: individual.net /DO46kL3iizbzx6PTphweAc1STdq9wyIknaBzhLK4+TeNiR7co
Cancel-Lock: sha1:S9MEXSDUKEXY4fr1qtzegze2daY=
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:78.0)
 Gecko/20100101 Thunderbird/78.12.0
In-Reply-To: <318e5e93-5f66-4bb8-8bf0-7ee3fd2688fan@googlegroups.com>
Content-Language: en-US
Xref: reader02.eternal-september.org comp.lang.ada:62417
List-Id: <comp.lang.ada>

On 2021-07-20 15:02, Richard Iswara wrote:
> I get this error on my program from the menu build => check semantic
> exponent must be of type Natural, found type "Standard.Float".
> 
> Should not 10 ** (log10 a + log10 b) = a*b?
> 
> This is my compiler build:
> 
> GNAT Studio Community 2020 (20200427) hosted on x86_64-pc-mingw32
> GNAT Community 2020 (20200429-93) targetting x86_64-pc-mingw32
> SPARK Community 2020 (20200429)
> 
> Here is the relevant part of program:
> 
> with Ada.Numerics.Elementary_Functions;
> use Ada.Numerics;


To make Ada.Numerics.Elementary_Functions."**" visible without 
qualification, you should also do "use Ada.Numerics.Elementary_Functions".

Otherwise the compiler will see only the predefined operator:

    function "**"(Left : Float; Right : Integer'Base) return Float

(see RM 4.5.6(9 and 10)) which explains why the compiler does not accept 
a floating-point value as the Right operand to "**".


> Logs : Float := 0.0;
> Multiples : Float;
    ...> Multiples := 10.0 ** Logs;  => this is where it fails


It fails because the compiler sees only the predefined "**" operator 
which has an integral right operand.