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<p>Hello, Cafe!</p>
<p>There is an opinion that Bool type has problems. It's
"dangerous", because it's not good to be used as flag for
success/fail result. I read this post:
<a class="moz-txt-link-freetext" href="https://existentialtype.wordpress.com/2011/03/15/boolean-blindness/">https://existentialtype.wordpress.com/2011/03/15/boolean-blindness/</a>
and was shocked. How popular is such opinion? Is it true, that
bool is "bad" type?</p>
<p>As I understand arguments of the post, Bool is bad because: 1)
you don't know what does True/False mean 2) after comparison you
get bit (!) only but then you may need to "recover" the comparing
value which was "shrink" to bit already.</p>
<p>Let's begin from 2. As I understand the author talks about one
register computers ;) if he have to "recover" a value. But shown
examples are in ML, where function arguments are bound to all
function body, so you don't need to "recover" anything, what was
bound as function argument or with "let". Sounds totally weird and
more close to psychology than to CS :)</p>
<p>Argument #1 is more interesting.</p>
<blockquote>
<p><tt><span style="color: rgb(51, 51, 51); font-size: 12px;
font-style: normal; font-variant-ligatures: normal;
font-variant-caps: normal; font-weight: 400; letter-spacing:
normal; text-align: left; text-indent: 0px; text-transform:
none; white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); text-decoration-style: initial;
text-decoration-color: initial; display: inline ! important;
float: none;">A Boolean,<span> </span></span></tt><tt><em
style="color: rgb(51, 51, 51); font-size: 12px;
font-variant-ligatures: normal; font-variant-caps: normal;
font-weight: 400; letter-spacing: normal; text-align: left;
text-indent: 0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(255, 255, 255); text-decoration-style:
initial; text-decoration-color: initial;">b</em></tt><tt><span
style="color: rgb(51, 51, 51); font-size: 12px; font-style:
normal; font-variant-ligatures: normal; font-variant-caps:
normal; font-weight: 400; letter-spacing: normal;
text-align: left; text-indent: 0px; text-transform: none;
white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); text-decoration-style: initial;
text-decoration-color: initial; display: inline ! important;
float: none;">, is either<span> </span></span></tt><tt><strong
style="color: rgb(51, 51, 51); font-size: 12px; font-style:
normal; font-variant-ligatures: normal; font-variant-caps:
normal; letter-spacing: normal; text-align: left;
text-indent: 0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(255, 255, 255); text-decoration-style:
initial; text-decoration-color: initial;">true</strong></tt><tt><span
style="color: rgb(51, 51, 51); font-size: 12px; font-style:
normal; font-variant-ligatures: normal; font-variant-caps:
normal; font-weight: 400; letter-spacing: normal;
text-align: left; text-indent: 0px; text-transform: none;
white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); text-decoration-style: initial;
text-decoration-color: initial; display: inline ! important;
float: none;">, or </span></tt><tt><strong style="color:
rgb(51, 51, 51); font-size: 12px; font-style: normal;
font-variant-ligatures: normal; font-variant-caps: normal;
letter-spacing: normal; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; word-spacing:
0px; -webkit-text-stroke-width: 0px; background-color:
rgb(255, 255, 255); text-decoration-style: initial;
text-decoration-color: initial;">false</strong></tt><tt><span
style="color: rgb(51, 51, 51); font-size: 12px; font-style:
normal; font-variant-ligatures: normal; font-variant-caps:
normal; font-weight: 400; letter-spacing: normal;
text-align: left; text-indent: 0px; text-transform: none;
white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); text-decoration-style: initial;
text-decoration-color: initial; display: inline ! important;
float: none;">; that’s it. There is no<span> </span></span></tt><tt><em
style="color: rgb(51, 51, 51); font-size: 12px;
font-variant-ligatures: normal; font-variant-caps: normal;
font-weight: 400; letter-spacing: normal; text-align: left;
text-indent: 0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(255, 255, 255); text-decoration-style:
initial; text-decoration-color: initial;">information</em></tt><tt><span
style="color: rgb(51, 51, 51); font-size: 12px; font-style:
normal; font-variant-ligatures: normal; font-variant-caps:
normal; font-weight: 400; letter-spacing: normal;
text-align: left; text-indent: 0px; text-transform: none;
white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); text-decoration-style: initial;
text-decoration-color: initial; display: inline ! important;
float: none;"><span> </span>carried by a Boolean beyond its
value, and that’s the rub. As Conor McBride puts it, to
make use of a Boolean you have to know its<span> </span></span></tt><tt><em
style="color: rgb(51, 51, 51); font-size: 12px;
font-variant-ligatures: normal; font-variant-caps: normal;
font-weight: 400; letter-spacing: normal; text-align: left;
text-indent: 0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(255, 255, 255); text-decoration-style:
initial; text-decoration-color: initial;">provenance<span> </span></em></tt><tt><span
style="color: rgb(51, 51, 51); font-size: 12px; font-style:
normal; font-variant-ligatures: normal; font-variant-caps:
normal; font-weight: 400; letter-spacing: normal;
text-align: left; text-indent: 0px; text-transform: none;
white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; background-color: rgb(255,
255, 255); text-decoration-style: initial;
text-decoration-color: initial; display: inline ! important;
float: none;">so that you can know what it<span> </span></span></tt><tt><em
style="color: rgb(51, 51, 51); font-size: 12px;
font-variant-ligatures: normal; font-variant-caps: normal;
font-weight: 400; letter-spacing: normal; text-align: left;
text-indent: 0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(255, 255, 255); text-decoration-style:
initial; text-decoration-color: initial;">means.</em></tt></p>
</blockquote>
<p>Really, what does True/False mean? How to find semantic of True?
It's very simple, because there is A) contract/interface which
interprets True/False and also B) there is a help from science.</p>
<p>A) There are a lot of languages (Unix shell, ML, Basic, Haskell,
C/C++...) with short-circuit expressions. Ex.,</p>
<blockquote><tt>e1 || e2</tt><tt><br>
</tt><tt>e1 && e2</tt><tt><br>
</tt><tt>e1 orelse e2</tt></blockquote>
<p>where interface is described by its operations: ||, &&,
orelse, etc and it has absolutely accurate and clear meaning: "||"
executes e2 iff e1 <b>fails, was not success</b>. "&&"
executes e2 iff e1 was succeeded. I don't use words "True" and
"False". Because, in different languages marker of success/fail is
different. For example, in Bash, the fail is any integer except 0.
In Haskell fail is False. In C is 0... What does mean False (and
True) is defined by contract/interface of short-circuit
operations, related to boolean algebra. A rare case when type is
bound with semantic! We read them literally (native English): e1
or-else e2!<br>
</p>
<p><b>This means that using of False to indicate success - is error!
And no way to miss provenance/knowledge what True or False
means.</b></p>
<p>(the same: what does Right/False mean?)<br>
</p>
<p>B) The help from science. Math (and CS) has own history. And one
of its mail-stones was birth of formal logic and then of Boolean
algebra. CS implemented those in declarative languages (Prolog,
for example). If we have some predicate in Prolog, "true" for that
predicate means "it was achieved", as goal. If that predicate has
side-effects, "true" means it was achieved, i.e. all its steps
(side-effects) were successfully executed. Predicate
write_text_to_file/2 is "true" when it wrote text to file. And no
way to return False on success or to think about sacral sense of
True/False :) And that sense traditionally is the same in all
programming language. If you invert it, you deny contract,
semantic and begin to use "inverted" logic :)</p>
<p>We can repeat the same logic with 3.1415926.. What does it mean?
Meaning, semantic is described, but contract/interface: this magic
irrational was born from part of algebra, called trigonometry. And
this algebra defines semantic of Pi, not programmer's usage of Pi,
programming context, etc. True/False semantic is defining by its
algebra: boolean. So, programmer should not change their semantic,
am I right?</p>
<p>So, my question is: is this post a april 1st trolling or author
was serious? :)</p>
<p>---</p>
<p>Best regards, Paul<br>
</p>
<p><br>
</p>
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