[SOLVED] .c error when compiling: %lf expects double but 2nd is char.

lleb · 06-06-2013, 01:04 PM

this is total bunk as i have zero char set. i only set double as that is all im using:

Code:

//The formula V=1/3lwh gives the volume (V) of a rectangular
//pyramid with length (l), width (w) and height (h)

//##########################################################
// Created by Raymond L. Brunkow 
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 2 or version 3 of the
// license, at your option.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
//##########################################################
#include<stdio.h>

//Problem Input
// double for l, w, h in meters
//Problem Output
// double in cubic meters
// Formula:  V=1/3*(l*w*h) or V=(double)1/(double)3*(l*w*h*) or V=(l*w*h*)/(double)3

int main(void)

{

	// setting variables
	double l, w, h, v;

	//get inputs for length, width, and height in meters.
	printf("\nPlease enter the (l)ength, (w)idth, and (h)eight in meters: \n");
	scanf("%lf", "%lf", "%lf", &l, &w, &h);

	//Formula for Volume of rectangular pyramid
	v = ( l * w * h ) / (double)3;

	// output 
	printf("\nThe volume of your rectangular pyramid with %.2f (l)ength, %.2f (w)idth, and %.2f (h)eight in meters is %.2f cubic meters.\n", l, w, h, v);

	sleep(5);

	return(0);

}

absolutely zero char set as variables, only double. double requires %lf, so that is exactly what im using. what is gcc doing?

error:

Code:

ssma-imac:ENG-3211 ssma$ gcc -o VOL volume_rectangular_pyramid.c 
volume_rectangular_pyramid.c: In function ‘main’:
volume_rectangular_pyramid.c:38: warning: writing into constant object (argument 2)
volume_rectangular_pyramid.c:38: warning: format ‘%lf’ expects type ‘double *’, but argument 2 has type ‘char *’

again i dont have a 'char *' type in my script.

no this is not homework, just practice. only homework this week is to read cpt 1-2, and 3.1/3.2 but i dont like going that long (3 weeks) without some kind of practice. im practicing the set type (double)3 in my equation line along with combining input/output on the same line of script.

H_TeXMeX_H · 06-06-2013, 01:20 PM

That's not how you use scanf. The first argument to scanf is a string containing what you want to scan. You have split this string across the first 3 arguments. Also note that you are missing an include of unistd.h, where sleep() is declared.

lleb · 06-06-2013, 01:30 PM

Quote:

Originally Posted by H_TeXMeX_H

That's not how you use scanf. The first argument to scanf is a string containing what you want to scan. You have split this string across the first 3 arguments. Also note that you are missing an include of unistd.h, where sleep() is declared.

ok im a bit confused, still very new to C, i was looking at an example the prof. gave last class with scanf:

Code:

double a, b, c, disc, root_1, root2;
foo
printf("Please enter a, b, and c: ");
scanf("%lf %lf %lf", &a, &b, &c);

i saw one error i made with "" around each %lf and ',' that didnt need to be there. still same error as before.

interesting, i have the sleep(n) in all of my scripts and have never had to use anything other then stdio.h

thank you. that did the trick. odd that with unistd.h not being in any of my other scripts that sleep(n) worked without a hitch. any idea's why that is?

edited to add the corrected code:

Code:

#include<unistd.h>


scanf("%lf %lf %lf", &l, &w, &h);

H_TeXMeX_H · 06-07-2013, 02:32 AM

Your version of gcc may be lenient by default and recognize the implied include of unistd.h. I've seen older versions error out. Either way, including it is the right thing to do.

lleb · 06-07-2013, 09:02 AM

thanks for the answer.