# New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Per...

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New Science Discovery: Perl Idiots Remain Idiots After A Decade!

A excerpt from the new book80=88Modern Perl=E3=80=89, just published, =
chapter 4
on80=9COperators=E2=80=9D. Quote:

=C2=ABThe associativity of an operator governs whether it evaluates from
left to right or right to left. Addition is left associative, such
that 2 + 3 + 4 evaluates 2 + 3 first, then adds 4 to the result.
Exponentiation is right associative, such that 2 ** 3 ** 4 evaluates 3
** 4 first, then raises 2 to the 81st power.BB

LOL. Looks like the perl folks haven't changed. Fundamentals of
serious math got botched so badly.

Let me explain the idiocy.

It says80=9CThe associativity of an operator governs whether it evalua=
tes
from left to right or right to left.=E2=80=9D. Ok, so let's say we have 2
operators: a white triangle96=B3 and a black triangle96=B2. Now, =
by the
perl's teaching above, let's suppose the white triangle is80=9Cright
associative=E2=80=9D and the black triangle is80=9Cleft associative=E2=
=80=9D. Now, look
at this:

396=B3 696=B2 5

seems like the white and black triangles are going to draw a pistol
and fight for the chick 6 there. LOL.

Now, let me tell you what operator precedence is. First of all, let's
limit ourselfs to discuss operators that are so-called binary
operators, which, in our context, basically means single symbol
operator that takes it's left and right side as operands. Now, each
symbol have a80=9Cprecedence=E2=80=9D, or in other words, the set of o=
perators
has a order. (one easy way to think of this is that, suppose you have
n symbols, then you give each a number, from 1 to n, as their order)
So, when 2 symbols are placed side by side such as80=8C396=B3 6 =
=E2=96=B2 5=E3=80=8D, the
symbol with higher precedence wins. Another easy way to think of this
is that each operator has a stickiness level. The higher its level, it
more sticky it is.

the problem with the perl explanations is that it's one misleading
confusion ball. It isn't about80=9Cleft/right associativity=E2=80=9D. =
It isn't
about80=9Cevaluates from left to right or right to left=E2=80=9D. Wors=
e, the word
=E2=80=9Cassociativity=E2=80=9D is a math term that describe a property of =
algebra
that has nothing to do with operator precedence, yet is easily
confused with because it is a property about order of evaluation. (for
example, the addition function is associative, meaning:80=8C(3+6)+5 =
=3D
3+(6+5)=E3=80=8D.)

compare it with this:

=E3=80=88PerlBC=86 Python: Complex Numbers=E3=80=89
http://xahlee.org/perl-python/complex_numbers.html

and for a good understanding of functions and operators, see:

=E3=80=88What's Function, What's Operator?=E3=80=89
http://xahlee.org/math/function_and_operators.html

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

On Wed, 29 Feb 2012 00:09:16 -0800, Xah Lee wrote:

Personally, I think this whole issue of precedence in a programming
language is over-rated.  It seems to me that grouping of any non-trivial
set of calculations should be done so as to remove any possible confusion
as to intent.  It is one more obstacle to accidental errors in logic,
where you intend one thing, possibly overlook precedence, and get a
strange result.

Sure, mathematically it *should* go a particular way, and any programming
language *should* follow that.  Still... they don't, and since they don't
it makes more sense to be really obvious what you meant to do.

As someone pointed out, a programming language is for humans; computers
don't need them.  That being the case, it makes sense to keep things as
clear as possible.

--
It's OKAY -- I'm an INTELLECTUAL, too.

## Re: New Science Discovery: Perl Detracters Remain Idiots After A Decade!

No. Mathematically it should go the way that it is defined to go.
There is nothing in Mathematics that either requires or prohibits
infix notation in programming languages, or even in Mathematical
notation.

Often infix notation with well thought out precedence is the clearest
way to go. RPN and the like have their place, but often are difficult
for real people to read.

--
Shmuel (Seymour J.) Metz, SysProg and JOAT  <http://patriot.net/~shmuel

Unsolicited bulk E-mail subject to legal action.  I reserve the
right to publicly post or ridicule any abusive E-mail.  Reply to
domain Patriot dot net user shmuel+news to contact me.  Do not

## Re: New Science Discovery: Perl Detracters Remain Idiots After A Decade!

On Wed, 29 Feb 2012 23:06:42 -0500, Shmuel (Seymour J.) Metz wrote:

Yes.  That (the mathematically defined way) is a particular way, is it
not?

However, I wasn't specifically referring to infix/postfix/prefix or
anything of that nature.  I wasn't limiting my comment to lisp notation
in particular, since what I said applies to any language.  I was
referring to the placement of parentheses (or other groupings) to
indicate to *humans* what the intended sequence of events was.  The
problem with precedence is that it is not always clear how it will go.
Different languages have different rules, some of which depart from the
rules in mathematics.  Some implementations of languages are buggy in
this regard.

Mathematically, and in any language with which I am familiar, the
sequence:  2 + 6 / 3 will yield 4.  It is unnecessary, but harmless, to
write this as 2 + (6 / 3).  A naive reader (or just a tired or hurried
one) might come up with 8 / 3 if there aren't any parentheses.

Whenever there is *any* possibility of ambiguity, I see no reason not to
clarify.  Back in the days when the way you wrote your code affected how
it was compiled, it made sense to rely heavily on language-specific
features, thus saving a few bytes.  With gigabyte memories, gigahertz
clock speeds, and optimizing compilers, the pressure to try to optimize
by hand is gone.  A few extra parentheses, or even breaking down a
complex sequence of events into discrete, simpler ones, is no longer a
costly luxury.  A few extra variables, if they help clarity, aren't going
to hurt anything.  Let the machine do the grunt work.  Pamper your
readers (which in a few weeks or months might be you) and show exactly
what you had in mind.  That's all I'm saying.

--
I'd just as soon kiss a Wookie.
-- Princess Leia Organa

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

On 2/29/2012 9:09, Xah Lee wrote:

Sorry, but you're wrong and they're right.
Associativity governs the order of evaluation of a group of operators
*OF THE SAME PRECEDENCE*.
If you write
2**3**4
only the fact the '**' is right associative will tell you that the order is
2**(3**4)
and not
(2**3)**4
I remind you that 2^(3^4) != (2^3)^4.

Kiuhnm

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

i missed a point in my original post. That is, when the same operator
are adjacent. e.g.80=8C396=B2 696=B2 5=E3=80=8D.

This is pointed out by Kiuhnm80=94kiuhnm03.4t.yahoo.it=E3=80=95 and Ti=
Thanks.

though, i disagree the way they expressed it, or any sense this is
different from math.

to clarify, amend my original post, here's what's needed for binary
operator precedence:

=E2=91=A0 the symbols are ordered. (e.g. given a unique integer)

=E2=91=A1 each symbol is has either one of left-side stickness or right-sid=
e
stickness spec. (needed when adjacent symbols are the same.)

About the lisp case mentioned by Tim, e.g.  in=E3=80=8C(f a b c)=E3=80=8D, =
whether it
means80=8C(f (f a b) c)=E3=80=8D or80=8C(f a (f b c))=E3=80=8D . =
It is not directly relevant
to the context of my original post, because it isn't about to
operators. It's about function argument eval order. Good point,
nevertheless.

the perl doc, is still misleading, terribly bad written. Becha ass!

Xah

On Feb 29, 4:08=C2=A0am, Kiuhnm <kiuhnm03.4t.yahoo.it> wrote:

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

On 3/1/2012 1:02, Xah Lee wrote:

They did not make up the terminology, if that is what you are saying.
The concepts of left and right associativity are well-known and accepted
in TCS (Theoretical CS).

If you change the terminology, no one will understand you unless you
provide your definitions every time (and then they may not accept them).

Another way of saying that an operator is left-associative is that its
parse tree is a left-tree, i.e. a complete tree where each right child
is a leaf.
For instance, (use a monospaced font)
1 + 2 + 3 + 4
gives you this left-tree:
+
+   4
+   3
1 2
while 1**2**3**4
gives you this right-tree:
**
1    **
2    **
3  4

Aho, Sethi and Ullman explain it this way in "Compilers: Principles,
Techniques and Tools":
"We say that the operator + associates to the left because an operand
with plus signs on both sides of it is taken by the operator to its
left. [...]"
And they also show parse trees similar to the ones I wrote above.

Kiuhnm

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

On Mar 1, 3:00=C2=A0am, Kiuhnm <kiuhnm03.4t.yahoo.it> wrote:

how do they explain when 2 operators are adjacent e.g.80=8C396=B3=
696=B2 580=8D?

do you happen to know some site that shows the relevant page i can
have a look?

thanks.

Xah

On Mar 1, 3:00=C2=A0am, Kiuhnm <kiuhnm03.4t.yahoo.it> wrote:

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

On 3/2/2012 14:12, Xah Lee wrote:

The same way you do, I guess. An operand that has operators on both
sides is operand of the operator of higher precedence.
For instance, in
3 * 4 + 6
4 is operand of * but not of +.
Indeed, the operands of + are 3*4 and 6.

Nope, sorry.

Kiuhnm

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

As the perlop manpage would have told you,

Operator associativity defines what happens if a sequence of the same
operators is used one after another

Since this is not the case in your example, it doesn't seem to be
applicable here. Also, the Perl I'm aware doesn't have 'white
triangle' and 'black triangle' operators and it also doesn't have
operators of equal precedence and different associativity. It can't,
actually, since there would be no way to evaluate an expression like
the mock one you invented above. Lastly, that something happens to be
in one way or another way in the completely arbitrary set of rules and
conventions commonly referred to as 'mathematics' (an essentially
outdated write-only programming language dating back to the times
when humans had to perform computations themselves) doesn't mean it is
of any relevance anywhere else just because of this, no matter how
dear it might be to lots of people.

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

On 2/29/2012 16:15, Rainer Weikusat wrote:

Theoretical Computer Science is a branch of mathematics. Are you saying
it is outdated?

Kiuhnm

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

On Wed, 29 Feb 2012 17:18:24 +0100, Kiuhnm wrote:

Neither mathematics nor computer science is outdated.  Such an assertion
is without merit.

Mathematics is not exclusively - nor even primarily - concerned with
computations.

--
Can anything be sadder than work left unfinished? Yes, work never begun.

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots Af

ROTF,LMAO! You obviously don't have a clue as to what Mathematics
means. Free hint: it doesn't mean Arithmetic. You're as bigoted as Xah
Lee,

--
Shmuel (Seymour J.) Metz, SysProg and JOAT  <http://patriot.net/~shmuel

Unsolicited bulk E-mail subject to legal action.  I reserve the
right to publicly post or ridicule any abusive E-mail.  Reply to
domain Patriot dot net user shmuel+news to contact me.  Do not

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots Af

On Wed, 29 Feb 2012 23:10:48 -0500, Shmuel (Seymour J.) Metz wrote:

Hmm... maybe, instead of just ridiculing him, you could explain where he
is mistaken.  Of course, doing that is a *LOT* harder than just calling
him a bigot.

BTW, I happen to agree with you insofar as this poster not understanding
the nature of mathematics.  His comment reminds me of the article,
"Transgressing the Boundaries: Towards a Transformative Hermeneutics of
Quantum Gravity" (http://www.physics.nyu.edu/sokal/transgress_v2 /
transgress_v2_singlefile.html).  Also known as the "Sokal Hoax."

--
Boling's postulate:
If you're feeling good, don't worry.  You'll get over it.

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots Af

On Thu, 01 Mar 2012 10:13:11 -0500, Shmuel (Seymour J.) Metz wrote:

OK.

What always gets me is how so many people criticized Sokal for doing it,
instead of soundly condemning the editor for not bothering to verify what
Sokal said.  It's like the kid points out that the emperor has no
clothes, so they shoot the kid.  Of course, in real life, that's exactly
what would happen, so I guess I shouldn't be too surprised...

--
It is a hard matter, my fellow citizens, to argue with the belly,
since it has no ears.
-- Marcus Porcius Cato

## Re: New Science Discovery: Perl Detractors Remain Idiots After A Decade!

On Fri, 02 Mar 2012 10:53:30 -0500, Shmuel (Seymour J.) Metz wrote:

Yeah, omerta... I'm familiar with it.  Talk and you're dead, and they put
a canary in your mouth (well, some folks do, anyway).

But of course you're right - it's a milder form of omerta.  It's just so
misguided.  Kill the messenger.  Imprison the whistle-blower.

--
Imitation is the sincerest form of plagiarism.

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots Af

You obviously don't have any sense of humour. But don't let this
trouble you.

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

associativity of operators mean little in the Lisp world obviously, so
why was this posted here?  Sorry, perl, python and emacs folks...

BTW, it's the same in javascript: it is so such that 2 + 3 + "4" is
"54" and "2" + 3 + 4 is "234".  Blame weak typing and + overloading,
though it may be a blessing.

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

On Wed, 29 Feb 2012 00:09:16 -0800, Xah Lee wrote:

Xah, you won't grow even an inch taller by cutting others down.

--
I joined scientology at a garage sale!!

## Re: New Science Discovery: Perl Idiots Remain Idiots After A Decade!New Science Discovery: Perl Idiots Remain Idiots After A Decade!

You're confused.

Associativity of operators is defined in mathematics.
(The same concept may be used in programming).
"left-associativity" and "right-associativity" are computer languages
concept and their definitions are not from mathematics.

Interestingly in mathematics associative means that it doesn't matter
whether you use (a.b).c or a.(b.c).
Using xxx-associativity to indicate that it *does* matter is
a bit perverse, but the Perl people are not to blame if they use
a term in their usual sense.

Groetjes Albert

--
--
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst