Float as Infinity

[The87Boy]

Hey all

I have a problem with float
I should write a program, where you are getting some numbers from the
command-line and try to find the maximum and minimum-values of these
numbers.
I need to initialize 2 floats (one with minus infinity and one with
plus infinity), or does anybody else have an idea?

I have made this code until now:
#include <stdio.h>

int main(void) {
int sat = 0;
float max = 0.0, x;
float min = plus-infinity;
printf ("Write some numbers:\n");

while( scanf("%f", &x) == 1) {

if (max<x) {
max=x;
}

if (sat == 0) {
min = x;
sat = 1;
} else {
if (min>x) {
min = x;
}
}
}

printf ("%f is max\n", max);
printf ("%f is min\n", min);
return 0;
}

[Eric Sosman]

The87Boy wrote On 09/25/07 03:25,:

On 24 Sep., 15:07, Eric Sosman <[e-mail] e:

>>The87Boy wrote:

>>>On 24 Sep., 13:15, r6144 <rainy6...@gmai l.comwrote:

The macro INFINITY defined in math.h should do (negative infinity is
simply -INFINITY). It is introduced in the newer ISO C99 standard, so
certain compilers might not have them or use some other name.

>>>Is there another way, I can do it then?

(The "it" that The87Boy trimmed away is initializing two
floating-point numbers to very large and very small values.)

Use HUGE_VAL and -HUGE_VAL, which will exist even on systems
where there are no representations for infinities. Note 1: If
you need float or long double instead of double, use HUGE_VALF
or HUGE_VALL if they exist, or FLT_MAX or LDBL_MAX otherwise.
Note 2: Do not confuse -FLT_MAX and -LDBL_MAX with FLT_MIN and
LDBL_MIN, which are small *positive* values. HUGE_VAL et al.
are in <math.h>, the others are in <float.h>.

What is the longest number, you can have in C?
And which data-type do I have to use then?

What do you mean by "longest?" Greatest value,
greatest precision, greatest amount of storage used,
something else?

And what do you mean by "number?" Natural numbers,
integers, floating-point numbers, complex numbers,
quaternions, ...?

And what do you mean by "in C?" Built into the
language and library, or implementable with them?

Rather than trying to answer these rhetorical
questions, try turning the problem around: What do
you want to *do* with this "longest number?" Choose
a hammer or choose a saw according to the job you want
to do, not according to which is "longer."

--
Er*********@sun .com

[user923005]

On Sep 25, 3:27 am, The87Boy <the87...@gmail .comwrote:

On 25 Sep., 12:15, user923005 <dcor...@connx. comwrote:

On Sep 25, 2:20 am, The87Boy <the87...@gmail .comwrote:

On 25 Sep., 10:22, user923005 <dcor...@connx. comwrote:

On Sep 25, 1:03 am, The87Boy <the87...@gmail .comwrote:

On 24 Sep., 15:07, Eric Sosman <[e-mail] e:

The87Boy wrote:
On 24 Sep., 13:15, r6144 <rainy6...@gmai l.comwrote:
>The macro INFINITY defined in math.h should do (negative infinity is
>simply -INFINITY). It is introduced in the newer ISO C99 standard, so
>certain compilers might not have them or use some other name.

Is there another way, I can do it then?

(The "it" that The87Boy trimmed away is initializing two
floating-point numbers to very large and very small values.)

Use HUGE_VAL and -HUGE_VAL, which will exist even on systems
where there are no representations for infinities. Note 1: If
you need float or long double instead of double, use HUGE_VALF
or HUGE_VALL if they exist, or FLT_MAX or LDBL_MAX otherwise.
Note 2: Do not confuse -FLT_MAX and -LDBL_MAX with FLT_MIN and
LDBL_MIN, which are small *positive* values. HUGE_VAL et al.
are in <math.h>, the others are in <float.h>.

What is the longest number, you can have in C?

There is no answer to your question. Data type double must hold at
least 1e37.

And which data-type do I have to use then?

What are the requirements for your data type?

It should only be numbers

Then declare some double variables, and do some tests:

if (valueMin value) /* do something */;
if (valueMax < value) /* do something */;

How can I initialize valueMin and valueMax

With an assignment.

[Richard Heathfield]

user923005 said:

On Sep 25, 3:27 am, The87Boy <the87...@gmail .comwrote:

<snipped 50-line quote for 1-line reply>

>>
How can I initialize valueMin and valueMax

With an assignment.

Context is always good, but in moderation.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Mark McIntyre]

On Tue, 25 Sep 2007 03:27:07 -0700, in comp.lang.c , The87Boy
<th******@gmail .comwrote:

>
How can I initialize valueMin and valueMax

This is NOT a C question. This is an algorithm question. If you don't
understand the algo, you cannot safely programme it, so take time to
understand the algo first. Here's a suggestion:

Pick ONE number.

Work out which of it is the min, and which is the max (easy....).
What are valueMin and valueMax set to now?

Once you've solved this step, pick a second number, and compare it.
--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan

[pete]

The87Boy wrote:

>
Hey all

I have a problem with float
I should write a program, where you are getting some numbers from the
command-line and try to find the maximum and minimum-values of these
numbers.

The first number entered is both the min and the max.

Any subsequent number entered
which is greater than the max, is the new max.

Any subsequent number entered
which is less than the min, is the new min.

--
pete

[user923005]

On Sep 25, 3:31 pm, pete <pfil...@mindsp ring.comwrote:

The87Boy wrote:

Hey all

I have a problem with float
I should write a program, where you are getting some numbers from the
command-line and try to find the maximum and minimum-values of these
numbers.

The first number entered is both the min and the max.

Any subsequent number entered
which is greater than the max, is the new max.

Any subsequent number entered
which is less than the min, is the new min.

Another common way of doing it (especially when you don't have an
array) is to set the minimum initially to be DBL_MAX and the maximum
to be DBL_MIN as defined in <float.hfor step 1. I think that this
is what the O.P. was getting at.

#include <float.h>
#include <stdio.h>
#include <stdlib.h>

char string[32767];
int main(void)
{
double valMin = DBL_MAX;
double valMax = DBL_MIN;
/*
read loop goes here...
comparisons reset valMin & valMax
*/
return 0;
}

[Barry Schwarz]

The87Boy wrote:

>
I have a problem with float. I should write a program, where you
are getting some numbers from the command-line and try to find the
maximum and minimum-values of these numbers.
I need to initialize 2 floats (one with minus infinity and one with
plus infinity), or does anybody else have an idea?

If the numbers are integers, use INT_MAX/MIN or LONG_MAX/MIN or
LLONG_MAX/MIN as appropriate. If they are floating type, use
FLT_MAX/MIN, DBL_MAX/MIN, or LDBL_MAX/MIN as appropriate.
Remove del for email

[Barry Schwarz]

On Tue, 25 Sep 2007 00:19:19 -0700, The87Boy <th******@gmail .com>
wrote:

>On 25 Sep., 01:44, CBFalconer <cbfalco...@yah oo.comwrote:

>The87Boy wrote:

I have a problem with float. I should write a program, where you
are getting some numbers from the command-line and try to find the
maximum and minimum-values of these numbers.
I need to initialize 2 floats (one with minus infinity and one with
plus infinity), or does anybody else have an idea?

... snip code ...

You don't need any infinities. Maintain two values, maxfound and
minfound. Get a single value from the user, and set maxfound and
minfound (both) to that value. From then on get an input value,
and if it is greater than maxfound, update maxfound. If it is less
than minfound, update minfound. Repeat until EOF on input. printf
max and minfound. Takes about 5 lines.

How can I initialize the values then?

You don't initialize the values or alternately it doesn't matter what
value you initialize them to. As soon as you read the first number,
you assign that value to both min and max and then process the rest of
the numbers through two if statements.
Remove del for email

[Keith Thompson]

Barry Schwarz <sc******@doezl .netwrites:

The87Boy wrote:

>I have a problem with float. I should write a program, where you
are getting some numbers from the command-line and try to find the
maximum and minimum-values of these numbers.
I need to initialize 2 floats (one with minus infinity and one with
plus infinity), or does anybody else have an idea?

If the numbers are integers, use INT_MAX/MIN or LONG_MAX/MIN or
LLONG_MAX/MIN as appropriate. If they are floating type, use
FLT_MAX/MIN, DBL_MAX/MIN, or LDBL_MAX/MIN as appropriate.

One problem with that approach is that it indicates that a sequence
with no elements has a minimum and maximum values of, say INT_MAX and
INT_MIN, respectively, which really doesn't make much sense. It's
better, IMHO, to report that there is no minumum or maximum value --
and if you're handling an empty sequence specially anyway, there's
less advantage in using the extreme values.

It makes the code depend on the element type, making it too easy to
forget to change the bounds when you change the type. And consider
trying to use the same algorithm for a sequence of "bignum" values
(arbitrary-precision numbers) where there are no minimum or maximum
values.

But it depends on the requirements. If the requirements say that
you're to return INT_MAX and INT_MIN for an empty list, then that's
what you do. And if the requirements are silent on the question,
either ask for clarification or do what you think makes the most sense
while leaving room for changes.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[The87Boy]

On 25 Sep., 20:58, Mark McIntyre <markmcint...@s pamcop.netwrote :

On Tue, 25 Sep 2007 03:27:07 -0700, in comp.lang.c , The87Boy

<the87...@gmail .comwrote:

How can I initialize valueMin and valueMax

This is NOT a C question. This is an algorithm question. If you don't
understand the algo, you cannot safely programme it, so take time to
understand the algo first. Here's a suggestion:

Pick ONE number.

Work out which of it is the min, and which is the max (easy....).
What are valueMin and valueMax set to now?

Once you've solved this step, pick a second number, and compare it.

It isn't the question, but should I set it to "float
valueMin=-999999999999999 99999999" or?