Thread: Double problem

I am new to programming, learning online and via books. Would appreciate help with this Double error, which states:

$g++ /tmp/13642987312818.cpp -o /tmp/13642987312818 -lm 2>&1
/tmp/13642987312818.cpp: In function 'int main()':
/tmp/13642987312818.cpp:33: error: expected primary-expression before 'double'
/tmp/13642987312818.cpp:33: error: expected `;' before 'double'

Code:

#include <stdio.h>
#include <math.h>

#define C 3

int main() 
{

  int v, w;
  float f;
  int i, e;
  double x;

      char n[4];
      printf ("Which species?\n");
      scanf(" %s",n);
      printf(" %s\n",n);
      printf ("What Vm?\n");
      scanf (" %d",&v);
      printf(" %d\n", v);

  printf("Conc in?\n");
  scanf(" %d",&i);
  printf(" %d\n", i);

  printf("Conc out?\n");
  scanf(" %d",&e);
  printf(" %d\n", e);

  w=i+e;

  x=double log(w);

  f = v - (C*x);

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

Input:
Ca2+
-60
15
150

Thanks !

I will answer my own question :
Remove previous Double declaration, and replace ln function with:
double x=log(w);