Interesting code

[v4vijayakumar]

Happened to see my old (last millennium) c code. Almost forgot that I
wrote it .
It is interesting. :-)

int sqrt(int no)
{
int t;
no = t * t;
return t;
}

[Bill Medland]

Keith Thompson wrote:

Ben Pfaff <bl*@cs.stanfor d.eduwrites:

>"Dh*********@g mail.com" <Dh*********@gm ail.comwrites:

>>v4vijayakum ar wrote:
int sqrt(int no)
{
int t;
no = t * t;
return t;
}

Can u tell me what is interesting in this code ??

Just the misconception that it illustrates.

Um, which one?

Apart from the multiple instances of undefined behavior, it's amusing
that the value it returns is (likely to be) the square root of the
parameter "no" -- though the value of the parameter "no" bears no
relationship to the argument with which the function was called.

I suppose the author assumed that an assigment statement causes the
left and right hand sides to become equal (by magic if necessary),
rather than merely evaluating the right operand and copying its value
to the object designated by the left operand. In other words, that
no = t * t;
would cause no to become equal t * t by changing the value of t;
obviously the way to do this is to set t to the square root of no.

To someone who knows what "=" means in mathematics, but hasn't been
exposed to the concept of assignment, it's not an entirely insane
misconception.

Which is why I liked the fact that Pascal used a symbol other than = to mean
assignment.

>
(Exercise: Design and implement a language that really works this
way.)

--
Bill Medland

[August Karlstrom]

Keith Thompson skrev:

To someone who knows what "=" means in mathematics, but hasn't been
exposed to the concept of assignment, it's not an entirely insane
misconception.

I'd say: "...hasn't been exposed to C's unfortunate choice of symbol for
assignment". ;-)
August

[Gordon Burditt]

>Happened to see my old (last millennium) c code. Almost forgot that I

>wrote it .
It is interesting. :-)

int sqrt(int no)
{
int t;
no = t * t;
return t;
}

This reminds me a bit of the hypothetical BUT statement which I
wanted to add to a language (FORTRAN at the time, but it could
sorta fit into C also):

y = a*x*x + b*x + c BUT y = 0;

would solve a quadratic equation. If a, b, and c weren't constants
there wasn't anything in particular that prohibited it from changing
them instead of x to satisfy the condition. There wasn't anything
guaranteeing which root you got, either, although you could do:

y = a*x*x + b*x + c BUT y = 0 and x 0;

Naturally, something like:

y = 0*x + 3 BUT y = 4;

is likely to have infinite run time.

[James Dow Allen]

v4vijayakumar wrote:

Happened to see my old (last millennium) c code. Almost forgot that I
wrote it .
It is interesting. :-)

I thought the pedantic responses to this were
perversely bizarre. Obviously vijay was joking;
beginners often have misconceptions; and it is
not impossible that some programming language
behave the way beginner vijay hoped.

Anyway, since the C compiler is free to set
undefined variables to any value, a minor change
to vijay's code makes it work:

#include <launch_codes.h >

/*
* This sqrt function relies
* on the Compiler obeying Asimov's
* First Law of Robotics.
*/

int sqrt(int no)
{
int t;
if (no == t * t)
return t;
else
aim_and_launch( "/dev/icbm", 1, TGT_TEHERAN);
}

James

[Chris Thomasson]

"James Dow Allen" <jd*********@ya hoo.comwrote in message
news:11******** **************@ h54g2000cwb.goo glegroups.com.. .
[...]

#include <launch_codes.h >

/*
* This sqrt function relies
* on the Compiler obeying Asimov's
* First Law of Robotics.
*/

int sqrt(int no)
{
int t;
if (no == t * t)
return t;
else
aim_and_launch( "/dev/icbm", 1, TGT_TEHERAN);
}

:O

[Richard Bos]

August Karlstrom <fu********@com hem.sewrote:

Keith Thompson skrev:

To someone who knows what "=" means in mathematics, but hasn't been
exposed to the concept of assignment, it's not an entirely insane
misconception.

I'd say: "...hasn't been exposed to C's unfortunate choice of symbol for
assignment". ;-)

You could say that, but don't more than half of all programming
languages which are used in practice (i.e., Intercal and Plankalkuel
don't count) share that choice of symbol? I'd rather call the assumption
that symbols must mean the same thing in maths and in programming
unfortunate. To use another example, {} is not just a higher-level form
of (), and [] and <have nothing to do with intervals.

Richard

[August Karlstrom]

Richard Bos skrev:

August Karlstrom <fu********@com hem.sewrote:

>I'd say: "...hasn't been exposed to C's unfortunate choice of symbol for
assignment". ;-)

You could say that, but don't more than half of all programming
languages which are used in practice (i.e., Intercal and Plankalkuel
don't count) share that choice of symbol?

Sure, and MTV plays the very best music too.

I'd rather call the assumption
that symbols must mean the same thing in maths and in programming
unfortunate.

The problem is that there are several cases in C where a well known
mathematical concept X with notation XM is notated with XC instead and
XM is defined to mean something different.

Mathematics Pascal/Modula/Oberon C
x = y x equals y x equals y x becomes y
1/2 0.5 0.5 0
August

[Richard Bos]

August Karlstrom <fu********@com hem.sewrote:

Richard Bos skrev:

August Karlstrom <fu********@com hem.sewrote:

I'd say: "...hasn't been exposed to C's unfortunate choice of symbol for
assignment". ;-)

You could say that, but don't more than half of all programming
languages which are used in practice (i.e., Intercal and Plankalkuel
don't count) share that choice of symbol?

Sure, and MTV plays the very best music too.

Who'se talking about the very best? That symbol _is_ used for
assignment, and it would be even if C had chosen <- instead. If you want
to be a good programmer, you'd better get used to computing not being
identical to maths.

Richard

[Harald van Dijk]

Richard Bos wrote:

August Karlstrom <fu********@com hem.sewrote:

Keith Thompson skrev:

To someone who knows what "=" means in mathematics, but hasn't been
exposed to the concept of assignment, it's not an entirely insane
misconception.

I'd say: "...hasn't been exposed to C's unfortunate choice of symbol for
assignment". ;-)

You could say that, but don't more than half of all programming
languages which are used in practice (i.e., Intercal and Plankalkuel
don't count) share that choice of symbol?

How many of those have copied their operators from C?

[CBFalconer]

Harald van D?k wrote:

Richard Bos wrote:

>August Karlstrom <fu********@com hem.sewrote:

>>Keith Thompson skrev:

To someone who knows what "=" means in mathematics, but hasn't
been exposed to the concept of assignment, it's not an entirely
insane misconception.

I'd say: "...hasn't been exposed to C's unfortunate choice of
symbol for assignment". ;-)

You could say that, but don't more than half of all programming
languages which are used in practice (i.e., Intercal and
Plankalkuel don't count) share that choice of symbol?

How many of those have copied their operators from C?

Which in turn copied its silly assignment operator from Fortran.

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net>