Strange output

[unique]

I have written some programs in c lang yet but today I get confused
with output i get.
I have function educate(..) which i call in main program this way:

J = educate(no_laye rs, no_neurons, input, output, lay, weights, 0.1,0);
printf("J= %f\n",J);

In the educate function i count J and i return it (but before I return
it I output it with printf):

float educate (int no_layers, int no_neurons[], float input[], float
output[], float* lay[], float* weights[], float gama, int debug) {
....
printf("J= %f\n",J);
return(J);
}

This is what i get:

J= 0.304447
J= 1050402944.0000 00

Is there any syntax prob? Why the values arent the same? :(

[Flash Gordon]

Re: Strange output

unique wrote:[color=blue]
> I have written some programs in c lang yet but today I get confused
> with output i get.
> I have function educate(..) which i call in main program this way:[/color]

<snip description of program>
[color=blue]
> This is what i get:
>
> J= 0.304447
> J= 1050402944.0000 00
>
> Is there any syntax prob? Why the values arent the same? :([/color]

Post a *complete* small program that exhibits your problem, NOT a
description. How are we to guess which of the many possible errors you
have committed if you don't show us your actual code?
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.

[unique]

Re: Strange output

I was investigating the problem a bit and the problem seems to be that
I call in file educate.c function educate(...) from the other file
neuron.c. I dont use any include, so code is here:
***test1.c***
float educate() {
float a=2.54f;
printf("a= %f", a);
return a;
}


***test2.c***
int main(int argc, char **argv) {
float b=educate();
printf("b= %f", b);
}

After compiling it with: cc test1.c test2.c -lm -o test2 and running it
the output is: a= 2.540000b= 1076006784.0000 00

So the problem is definitely in including file test2... how can i
include it right? what's going on in my example?

Thank you for your reply
Flash Gordon wrote:[color=blue]
> unique wrote:[color=green]
> > I have written some programs in c lang yet but today I get confused
> > with output i get.
> > I have function educate(..) which i call in main program this way:[/color]
>
> <snip description of program>
>[color=green]
> > This is what i get:
> >
> > J= 0.304447
> > J= 1050402944.0000 00
> >
> > Is there any syntax prob? Why the values arent the same? :([/color]
>
> Post a *complete* small program that exhibits your problem, NOT a
> description. How are we to guess which of the many possible errors you
> have committed if you don't show us your actual code?
> --
> Flash Gordon
> Living in interesting times.
> Although my email address says spam, it is real and I read it.[/color]

[pete]

Re: Strange output

Flash Gordon wrote:[color=blue]
>
> unique wrote:[color=green]
> > I have written some programs in c lang yet but today I get confused
> > with output i get.
> > I have function educate(..) which i call in main program this way:[/color]
>
> <snip description of program>
>[color=green]
> > This is what i get:
> >
> > J= 0.304447
> > J= 1050402944.0000 00
> >
> > Is there any syntax prob? Why the values arent the same? :([/color]
>
> Post a *complete* small program that exhibits your problem, NOT a
> description. How are we to guess which of the many possible errors you
> have committed if you don't show us your actual code?[/color]

My guess is that changing the declaration of all of
the float type objects, to type double, will fix the problem.

I avoid the small arithmetic types, :

char
unsigned char
/* Especially these next 4 */
signed char
short
unsigned short
float

unless there's a special reason.
The problem is that those types tend to get promoted a lot.

Strings are a special enough reason to use type char.
Reading and/or writing bytes in raw memory
is a good reason to use unsigned char.

--
pete

[pete]

Re: Strange output

unique wrote:[color=blue]
>
> I was investigating the problem a bit and the problem seems to be that
> I call in file educate.c function educate(...) from the other file
> neuron.c. I dont use any include, so code is here:
> ***test1.c***
> float educate() {
> float a=2.54f;
> printf("a= %f", a);
> return a;
> }
>
> ***test2.c***
> int main(int argc, char **argv) {
> float b=educate();
> printf("b= %f", b);
> }
>
> After compiling it with:
> cc test1.c test2.c -lm -o test2 and running it[/color]

What does "cc test1.c test2.c -lm -o test2" mean?
[color=blue]
> the output is: a= 2.540000b= 1076006784.0000 00
>
> So the problem is definitely in including file test2...
> how can i include it right? what's going on in my example?[/color]

I don't see #include <stdio.h> in either file,
so both files are undefined.
[color=blue][color=green]
> > Post a *complete* small program that exhibits your problem, NOT a
> > description.
> > How are we to guess which of the many possible errors you
> > have committed if you don't show us your actual code?[/color][/color]

--
pete

[Skarmander]

Re: Strange output

unique wrote:[color=blue]
> I was investigating the problem a bit and the problem seems to be that
> I call in file educate.c function educate(...) from the other file
> neuron.c. I dont use any include, so code is here:
> ***test1.c***
> float educate() {
> float a=2.54f;
> printf("a= %f", a);
> return a;
> }
>
>
> ***test2.c***
> int main(int argc, char **argv) {
> float b=educate();
> printf("b= %f", b);
> }
>
> After compiling it with: cc test1.c test2.c -lm -o test2 and running it
> the output is: a= 2.540000b= 1076006784.0000 00
>
> So the problem is definitely in including file test2... how can i
> include it right? what's going on in my example?
>[/color]
<snip>
What's going on is that the compiler doesn't know what sort of function
educate() is when it's compiling test2.c. In C, units are compiled one
at a time, even if you pass multiple to the compiler.

So the compiler must assume a default of educate() returning an int,
which of course it doesn't. The bits that make up the float are then
interpreted as an int and converted back to a float. To fix this, you
should add a function prototype, like so:

test2.c:
float educate(void);

int main(int argc, char **argv) {
float b=educate();
printf("b= %f", b);
return 0;
}

But good style is to put prototypes of functions accessed by other units
in headers and include them:

test1.h:
float educate(void);

test2.c:
#include "test1.h"

int main(...

Read any good book on C that talks about functions and prototypes for more.

S.

[unique]

Re: Strange output

> So the compiler must assume a default of educate() returning an int,
which of course it doesn't.

Thank you very much Skarmander, you are completely right, i solved it
with header file.

Have a gr8 day all

[Flash Gordon]

Re: Strange output

unique wrote:

Your reply belongs *after* the text you are replying to, not before,
after deleting (snipping) the text you are not replying to.
[color=blue]
> I was investigating the problem a bit and the problem seems to be that
> I call in file educate.c function educate(...) from the other file
> neuron.c. I dont use any include, so code is here:
> ***test1.c***[/color]

#include <stdio.h>
#include <test1.h>

I'll explain the reasons for these further down.
[color=blue]
> float educate() {[/color]

If it doesn't take parameters it is better to explicitly say so.
float educate(void)
{
[color=blue]
> float a=2.54f;
> printf("a= %f", a);[/color]

printf is a varidac function and *requires* a prototype in scope. The
normal way to do this is to include stdio.h at or about the top of the
source file.
[color=blue]
> return a;
> }
>
>
> ***test2.c***[/color]

#include <stdio.h>
#include <test1.h>

I'll explain the reasons for these further down.
[color=blue]
> int main(int argc, char **argv) {[/color]

You are not using the parameters, so you might as well say so.
int main(void)
{

Note that main returns and int (no other return value including void is
standard).
[color=blue]
> float b=educate();[/color]

There is no prototype for educate in scope, so the compiler is
*required* to assume it returns an int. Since it does not the behaviour
is undefined and the effect in your case is that b is assigned a garbage
value. The standard way to deal with this is using a header file such as
the one I show below and to include it in *both* the file defining the
function (to ensure the prototype matches) and the file from which it is
called. If your C text book (and/or tutor) does not explain this they
need to be replaced.
[color=blue]
> printf("b= %f", b);[/color]

Again, the prototype is required for printf.
[color=blue]
> }
>
> After compiling it with: cc test1.c test2.c -lm -o test2 and running it
> the output is: a= 2.540000b= 1076006784.0000 00
>
> So the problem is definitely in including file test2... how can i
> include it right? what's going on in my example?[/color]

<snip>

Having made the above changes you create a header file which provides a
prototype for educate:

/* test1.h */
#ifdef TEST1_H
#define TEST1_H
float educate(void);
#endif

Then the compiler knows what is going on.

To understand the reason for the #ifdef etc search for include guards.

I also suggest reading the comp.lang.c FAQ (google will find it) and
K&R2 (the FAQ will tell you what that is).
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.

[Martin Ambuhl]

Re: Strange output

unique wrote:[color=blue]
> I have written some programs in c lang yet but today I get confused
> with output i get.
> I have function educate(..) which i call in main program this way:
>
> J = educate(no_laye rs, no_neurons, input, output, lay, weights, 0.1,0);
> printf("J= %f\n",J);
>
> In the educate function i count J and i return it (but before I return
> it I output it with printf):
>
> float educate (int no_layers, int no_neurons[], float input[], float
> output[], float* lay[], float* weights[], float gama, int debug) {
> ...
> printf("J= %f\n",J);
> return(J);
> }
>
> This is what i get:
>
> J= 0.304447
> J= 1050402944.0000 00
>
> Is there any syntax prob? Why the values arent the same? :(
>[/color]

$oracle -n
---
---
---
---
-X-
- -

(MWD)
Jian over Gen
3 Yuan 'Wielding'
Wielding: Receipt; little beneficial to determine.

(WB)
Qian over Gen
33 Dun 'Withdrawal'
Withdrawal: prevalence is had. It is fitting
to practice constancy in small matters.

Transforming:
second yin
(MWD) Uphold it using a yellow ox's bridle;
no one will succeed in overturning it,

(WB) If one holds then with yellow ox hide,
none will manage to break away.

Approaches:
---
---
---
---
---
- -
(MWD)
Jian over Suan
8 Gou 'Meeting'
[Meeting]: The maiden matures; do not herewith take
a maiden.

(WB)
Qian over Sun
44 Gou 'Encounter'
Encounter: the woman is strong; it would not do to
marry this woman.

$

[Martin Ambuhl]

Re: Strange output

unique wrote:[color=blue]
> I was investigating the problem a bit and the problem seems to be that
> I call in file educate.c function educate(...) from the other file
> neuron.c. I dont use any include, so code is here:
> ***test1.c***
> float educate() {
> float a=2.54f;
> printf("a= %f", a);
> return a;
> }
>
>
> ***test2.c***
> int main(int argc, char **argv) {
> float b=educate();
> printf("b= %f", b);
> }
>
> After compiling it with: cc test1.c test2.c -lm -o test2 and running it
> the output is: a= 2.540000b= 1076006784.0000 00
>
> So the problem is definitely in including file test2[/color]

WRONG! Your problem is the failure to provide a declaration for
educate() in test2.c. The educate() function test2 knows about returns
an int (in C89; your code is just broken in C99), while educate() in
test1.c returns a float.

Your code is broken even if you include a declaration for educate() in
test2.c, since you fail to provide the required declaration for the
variadic function printf(); that's what <stdio.h> is for.

[Barry Schwarz]

Re: Strange output

On 9 Oct 2005 06:39:15 -0700, "unique" <julius4@gmail. com> wrote:
[color=blue][color=green]
>> So the compiler must assume a default of educate() returning an int,[/color]
>which of course it doesn't.
>
>Thank you very much Skarmander, you are completely right, i solved it
>with header file.
>[/color]
In addition to solving it this time, you should up the warning level
of your compiler so that it tells anytime you invoke a function for
which a prototype is not in scope.


<<Remove the del for email>>

[Emmanuel Delahaye]

Re: Strange output

unique a écrit :[color=blue]
> I was investigating the problem a bit and the problem seems to be that
> I call in file educate.c function educate(...) from the other file
> neuron.c. I dont use any include, so code is here:
> ***test1.c***
> float educate() {
> float a=2.54f;
> printf("a= %f", a);
> return a;
> }
>
>
> ***test2.c***
> int main(int argc, char **argv) {
> float b=educate();
> printf("b= %f", b);
> }
>
> After compiling it with: cc test1.c test2.c -lm -o test2 and running it
> the output is: a= 2.540000b= 1076006784.0000 00[/color]

This works fine to me (single compile unit)

#include <stdio.h>

float educate(void)
{
float a=2.54f;
printf("a= %f\n", a);
return a;
}

int main(void)
{
float b=educate();
printf("b= %f\n", b);
}

Now, if you are gooing to use 2 separated compile units (CUs), you must
define a protoype in a common file called a header. This is the proper
way of doing it:

/* educate.h */
#ifndef H_EDUCATE
#define H_EDUCATE

/* function prototypes */
float educate(void);

#endif /* guard */

Then you must include this header in the definition CU (for consistency)
and in all user CU:

/* educate.c */
#include <stdio.h>
#include "educate.h"
float educate(void)
{
float a=2.54f;
printf("a= %f\n", a);
return a;
}

/* main.c */
#include <stdio.h>
#include "educate.h"

int main(void)
{
float b=educate();
printf("b= %f\n", b);
return 0;
}

[Emmanuel Delahaye]

Re: Strange output

unique a écrit :[color=blue]
> I was investigating the problem a bit and the problem seems to be that
> I call in file educate.c function educate(...) from the other file
> neuron.c. I dont use any include, so code is here:
> ***test1.c***
> float educate() {
> float a=2.54f;
> printf("a= %f", a);
> return a;
> }
>
>
> ***test2.c***
> int main(int argc, char **argv) {
> float b=educate();
> printf("b= %f", b);
> }
>
> After compiling it with: cc test1.c test2.c -lm -o test2 and running it
> the output is: a= 2.540000b= 1076006784.0000 00[/color]

This works fine to me (single compile unit)

#include <stdio.h>

float educate(void)
{
float a=2.54f;
printf("a= %f\n", a);
return a;
}

int main(void)
{
float b=educate();
printf("b= %f\n", b);
}

Now, if you are going to use two separated compile units (CUs), you must
define a protoype in a common file called a header. This is the proper
way of doing it (the guard protects agains multiple inclusions in a
single CU):

/* educate.h */
#ifndef H_EDUCATE
#define H_EDUCATE

/* function prototypes */
float educate(void);

#endif /* guard */

Then you must include this header in the definition CU (for consistency)
and in all user CU:

/* educate.c */
#include <stdio.h>
#include "educate.h"
float educate(void)
{
float a=2.54f;
printf("a= %f\n", a);
return a;
}

/* main.c */
#include <stdio.h>
#include "educate.h"

int main(void)
{
float b=educate();
printf("b= %f\n", b);
return 0;
}