Question

In my my program, I am simply reading wind direction from a sensor. I am having trouble printing out the English version of the direction. The basic algorithm is this:

(values are in degrees, read from a struct)

string direction;  (I know you have to create a char array, just not sure how)

if(sensor.windir > 11 && sensor.windspeed < 34)
 {
 direction = "NNE";
 }

  if(sensor.windir > 34 && sensor.windspeed < 57)
 {
 direction = "NE";
 }



  .....


 printf(" Current windir is %s\n", direction);

I’m rusty on C and need a refresher on how to print the wind direction string based on its value range defined in the “if” statements. I will not need more than 3 chars in my string.

Answer 1

For your problem at hand, the following will do:

char const * s = "[error]";

if (speed => 1 && speed < 13)       { s = "NW"; }
else if (speed >= 13 && speed < 27) { s = "NE"; }
else if (speed >= 27 && speed < 39) { s = "NS"; }

printf("The direction is %s.\n", s);

This only works for compile-time constant string literals.

If you need to create dynamic strings, you need to create a char array (like char buf[1024];) and use something like snprintf to populate it with a string.