GCC compiler giving syntax error before 'double' error

On my Linux computer, I am using the command:

gcc programname.c -lm

for the following code:

Code:

#include<time.h>

#include<stdio.h>

#include<math.h>

#include<stdlib.h>



int main(void)

{



int p, d, h, what, end, steps;

double i, n, M, c, w, q, measure;

end = 2000;

steps = 1000;

double average1[end][2], average2[end][2];

int width[end][steps];



//w is equal to the possible number of ways to choose a reactant molecule,

// which in our case is equal to how many molecules exist in the system

w = 0;



what = 10000;

measure = 0.01;



//c defines the propensity of the reaction (change to 0.5, 1.0, and 10)

c = 10;



q = 0;

//concentration

int cnctrn;

cnctrn = 1000;
srand((unsigned int)time(NULL));

for (d = 0; d < end; d++){

for (h = 0; h < 2; h++){

average1[d][h] = 0;

average2[d][h] = 0;

}

}

for (p = 0; p < end; p++){

for (d = 0; d < steps; d++){

width[p][d] = 0;

}

}





for (p = 1; p < steps; p++){



width[0][p] = cnctrn;

}





//PLotting in Matlab

FILE * pFile;

char name [100];

pFile = fopen ("Gillespie.txt","w");



n = 0;

d = 0;



for (h = 0; h < steps; h++){



while (i < what && cnctrn > 1){



q = double((rand())/(double(RAND_MAX + 1)));





for (d = 0; d < end; d = d+1){

if ( i < (d+1)*measure && i >= d*measure){

width[d][h] = cnctrn;

}

}

//exact data comparison

w = cnctrn*c;

M = -log(q)/w;

cnctrn = cnctrn-1;



i = i + M;

n = n + 1;

fprintf(pFile, "%f %i\n ", i, cnctrn);

}

}

for (p = 1; p < end; p++){

for (d = 0; d < steps; d++){

if (width[p][d] == 0){

width[p][d] = width[p][d-1];

}

}

}

fclose (pFile);



for (d = 0; d < end; d++){

average1[d][0] = d*measure;

average2[d][0] = d*measure;

}







for (d = 0; d < end; d++){

for (h = 0; h<steps; h++){

average1[d][1] = average1[d][1] + double(width[d][h])/double(steps);

average2[d][1]=average2[d][1]+

double(width[d][h])*double(width[d][h])/double(steps);

}

}





pFile = fopen ("average.txt","w");

for (d = 0; d < end; d++){

fprintf(pFile, "%f %f\n ", average1[d][0], average1[d][1]);

}

fclose (pFile);

pFile = fopen ("averagesquared.txt","w");

for (d = 0; d < end; d++){

fprintf(pFile, "%f %f\n ", average2[d][0], average2[d][1]);

}

fclose (pFile);

}

I keep getting this error for the lines I put in bold:
syntax error before 'double'



Putting (double) in parenthesis gets rid of the error, but outputs the wrong text files. How do I fix this error without just putting the (double) in parenthesis to get the correct output?
Any help with this would be very very appreciated! Thanks!

Gah! Indent, indent, indent your code!

This line:

Code:

q = double((rand())/(double(RAND_MAX + 1)));

You probably want casts... you're trying to use a type as a function. (Looks like C++, but you're compiling as C - What language do you want?) In C, this would probably be:

Code:

q = (double) rand() / (double) (RAND_MAX + 1);

q will then be a random from [0,1).

EDIT: You're also allocating over 7.5MB of data on the stack. You have either a large stack, or may very well overflow it on some system. (Like mine.) (Not sure what the defaults are...)

Also, things like:

Code:

	for (d = 0; d < end; d++)
	{

		for (h = 0; h < 2; h++)
		{
			average1[d][h] = 0;
			average2[d][h] = 0;
		}
	}

Since you're setting the entire thing to zero, in C, you can do:

Code:

memset(average1, 0, sizeof(average1);
memset(average1, 0, sizeof(average2);

...or simply initialize the array to zero when you declare it:

Code:

int myarray[50] = {0};

Originally Posted by Cactus_Hugger

Since you're setting the entire thing to zero, in C, you can do:

Code:

memset(average1, 0, sizeof(average1);
memset(average1, 0, sizeof(average2);

Not the best choice for floating point. Zero-filling does not guarantee floating-point zeros.

so I made those changes, putting (double) in parenthesis, but now I get the integer overflow error. how would i fix that? and the only way I am able to open my text files is by double clicking the a.out file that is created when I compile it, then the three text files appear. by the way, this is c code.

http://c-faq.com/lib/randrange.html
http://eternallyconfuzzled.com/arts/jsw_art_rand.aspx
http://c-faq.com/lib/rand48.html