Path: csiph.com!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.programming
Subject: Re: =?utf-8?Q?=E2=80=9CBooleans?= Considered =?utf-8?Q?Harmful?= =?utf-8?Q?=E2=80=9D?=
Date: Thu, 22 May 2025 12:27:16 -0700
Organization: None to speak of
Lines: 60
Message-ID: <87frgwxx7v.fsf@nosuchdomain.example.com>
References: <100mhh5$3b9hp$3@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain
Injection-Date: Thu, 22 May 2025 21:27:21 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="dae22f89fe428551773c9395a452d8f1"; logging-data="3816967"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX197jN7tO9KlyYq+ogGAM950"
User-Agent: Gnus/5.13 (Gnus v5.13)
Cancel-Lock: sha1:t4dbhgB2qE3p8D54IKi2EOFb3HE= sha1:88Agfcv2Rriw7PFv7ict0jc/pGo=
Xref: csiph.com comp.programming:16779

Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> I think most of this article is a load of nonsense, myself.
>
> <https://www.infoworld.com/article/3990923/booleans-considered-harmful.html>
>
> Thoughts?

It's not *all* nonsense.

> 1. Stay positive
> 2. Put positive first

Ok, sure.  UserIsAuthorized is clearer than !UserIsNotAuthorized.

> 3. No complex expressions

Meh.  The example he gives is:

    if (user.age > 18 && user.isActive && !user.isBanned && user.subscriptionLevel >= 2) {
      grantAccess();
    }

I don't find that particularly problematic.  His suggestion to replace
each subexpression with a named constant isn't horrible, and it can be
useful in some cases, but it can also add clutter.

Note that the first three points are advice about how to use Booleans
clearly, not about avoiding them.  I guess a "Foo considered harmful"
title was too tempting.

> 4. Say no to Boolean parameters

This is perhaps his most valid point.  I agree that

    saveUser(user, true, false);

is too obscure.  But for languages that support them, named parameter
associations neatly solve the problem:

    saveUser(user, sendEmail = true, verified = false);

Unfortunately, a lot of very popular languages don't have this feature.

Comments are an alternative, but not a good one; it's too easy for them
to get out of sync with the code.

> 5. Booleans are a trap for future complexity

*Anything* could be a trap for future complexity.  The example is
a Boolean "isSmallDrink", which needs to be changed when the boss
announces we're going to be serving small, medium, and large drinks.

I agree that a 2-element emum (small, large) would have been clearer
and more extensible.  But refactoring is a thing, and revisiting
an earlier decision (changing the type of a variable) is something
that has to be done all the time.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */