Passing FLOAT's

pjot · Post by **pjot** » Sat Nov 06, 2004 4:21 pm

Hi,

Using this Shared Object:

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

int int_print (int i)
{
printf("%d\n", i);
return(0);
}
int float_print (float f)
{
printf("%f\n", f);
return(0);
}

...and the following newLisp code:

Code: Select all

#!/usr/bin/newlisp
(import "./lib.so" "int_print")
(import "./lib.so" "float_print")
(int_print 345)
(float_print 1.2)
(exit)

...delivers this result:
345
0.000000

It seems that passing a float to a C function does not work? Or is there something wrong in the code?

Also, is it possible to pass an array to a C function?

Peter

pjot · Post by **pjot** » Sat Nov 06, 2004 4:37 pm

Passing an INT array to a C function works:

Code: Select all

C-code:

int array_print (int i[])
{
printf("%d\n", i[0]);
printf("%d\n", i[1]);
return(0);
}
--------------------------------------------------
NewLisp:

(import "./lib.so" "array_print")
(array_print (append (pack "lu" 16432) (pack "lu" 54321)))

An array with floats also works fine this way. Now for the single floats.... ;-)

eddier · Post by **eddier** » Sat Nov 06, 2004 4:40 pm

I've seen this error (%f and double) or (%lf and float) many times in plain C. I bet if you change float to double you will have no problem.

Eddie

pjot · Post by **pjot** » Sat Nov 06, 2004 4:47 pm

No; suppose I change my C-function this way:

Code: Select all

int float_print (float f)
{
printf("%f\n", f);
printf("%g\n", f);
printf("%e\n", f);
return(0);
------------------------------------------
(import "./float.so" "float_print")
(float_print 1.2)
}

Then the result is:
0.000000
4.17233e-08
4.172325e-08

Strange! Also PACKing within newLisp does not help me here.

eddier · Post by **eddier** » Sat Nov 06, 2004 5:21 pm

Yes, but doesn't newlisp use doubles internally and not floats?
in (float_print 1.2) the 1.2 is being passed as a double isn't it?

Eddie

pjot · Post by **pjot** » Sat Nov 06, 2004 5:29 pm

So you mean it's never going to work anyway?

Even if it is passed as double, at least one of the PRINTF modifiers should show the number correctly then?

newdep · Post by **newdep** » Sat Nov 06, 2004 5:29 pm

looks like an "Endian" issue to me...

Lutz · Post by **Lutz** » Sat Nov 06, 2004 5:33 pm

Code: Select all

int float_print(double num)
{
printf(">>%lf<<", num);

return(0);
}

gcc test.c -shared -o testlib.so

newLISP v.8.2.6 Copyright (c) 2004 Lutz Mueller. All rights reserved.

> (import "/usr/home/nuevatec/testlib.so" "float_print")
float_print <281A153C>
> (float_print 1.234)
>>1.234000<<0

>

Eddie is right: newLISP uses double

Lutz

newdep · Post by **newdep** » Sat Nov 06, 2004 5:34 pm

never take a posting too literaly...:-)

> (unpack "lf" 1.2)
Segmentation fault

:-)

pjot · Post by **pjot** » Sat Nov 06, 2004 5:36 pm

Yes I understand, but this is too bad; it means that many C-library's cannot accept a 'float' coming in from newLisp. There are functions which declare their arguments as float, I cannot pass float values to them.

Lutz · Post by **Lutz** » Sat Nov 06, 2004 5:41 pm

yes you can:

(get-integer (pack "f" 1.23)) => 1067282596

The integer coming out is what you pass to the function which takes float.

Lutz

pjot · Post by **pjot** » Sat Nov 06, 2004 5:43 pm

Great! This is what I was looking for.

Thanks Lutz!!

Lutz · Post by **Lutz** » Sat Nov 06, 2004 5:47 pm

Sorry doesn't work ... but should ... investigating ...

Lutz

newdep · Post by **newdep** » Sat Nov 06, 2004 5:52 pm

.. its floating segmf's today...:-)

> (get-integer (get-float (pack "lf" (float 12314127.641234))))
Segmentation fault

Lutz · Post by **Lutz** » Sat Nov 06, 2004 5:57 pm

Works just fine, I forgot to compile:

#include <stdio.h>

int float_print(float num)
{
printf(">>%f<<", num);

return(0);
}

> (import "/usr/home/nuevatec/testlib.so" "float_print")
float_print <281A153C>
> (float_print (get-integer (pack "f" 1.234)))
>>1.234000<<0
>

Lutz

pjot · Post by **pjot** » Sat Nov 06, 2004 5:58 pm

I don't want to be disturbing but it works for me!

Code: Select all

int float_print (float f)
{
printf("%f\n", f);
printf("%g\n", f);
printf("%e\n", f);
return(0);
}
-----------------------------------------------
NewLisp:
(import "./float.so" "float_print")
(float_print (get-integer (pack "f" 1.23)))

Result:
1.230000
1.23
1.230000e+00

Lutz · Post by **Lutz** » Sat Nov 06, 2004 5:58 pm

Norman, Norman ... too much of that dark beer ;)

Lutz

Lutz · Post by **Lutz** » Sat Nov 06, 2004 5:59 pm

yes, it works just fine, I forgot to compile

Lutz

pjot · Post by **pjot** » Sat Nov 06, 2004 5:59 pm

Yeah he is drinking too much... ;-)

newdep · Post by **newdep** » Sat Nov 06, 2004 6:06 pm

Yes we call it "Dentergems Double" But it floats good ;-)

Lutz · Post by **Lutz** » Sat Nov 06, 2004 6:09 pm

I am still waiting for that case of "Dentergems Double" you guys promised me some time ago ...

Lutz

newdep · Post by **newdep** » Sat Nov 06, 2004 6:11 pm

Heee Lutz yes your right ;-)

Pjot..how about it? Your traveling to the states next week!
Cant you post a case for Lutz?

pjot · Post by **pjot** » Sat Nov 06, 2004 6:12 pm

Well, I will be in Utah, not Florida unfortunately... ;-)

Lutz · Post by **Lutz** » Sat Nov 06, 2004 6:16 pm

In Utah on Sundays they don't serve beer with more than 6% alcohol content . In Florida they don't sell beer in supermarkets before noon on Sundays (so people don't come drunken to church :) )

Lutz

newdep · Post by **newdep** » Sat Nov 06, 2004 6:19 pm

hahahah..sounds logic... Well here in The Netherlands we have this standard
environment-rule "where a church is is a bar" ;-) So actualy every town with a church
has the bar across the street ;-) Im wont explain the results ;-)