Thread: functions using arrays

Sorry...i have all of the errors and warnings on that my
teacher told us to use (-ansi, -pedantic,-errors,-Werror,-Wall)
I too am making a calculator and I looked the other threads
about calculators and mine is not that complicated because
we haven't learned some of those things but anyway.
we have to do ours in functions. i've wriiten these functions
using arrays because the input is coming at a max of 20 for
all functions accept the power function. I think my power
function is wrong because it's not doing the right thing
also i think my other functions are missing something. any ideas?
thank you.

Code:

float power_func(float firsval, int seconval){                                                                                                 
  int count;                                                                                                                                   
  float powerval;                                                                                                                              
  if (firsval < 0){                                                                                                                            
    firsval = -1;                                                                                                                              
    seconval= 1/seconval;                                                                                                                      
  }                                                                                                                                            
  for(count = 0; count < firsval; count++){                                                                                                    
    powerval *= seconval;                                                                                                                      
  }                                                                                                                                            
  return powerval;                                                                                                                             
}    
                                                                                                                                               
float add_arr(float adarry[]){                                                                                                                 
  int count;                                                                                                                                   
  float sum = adarry[0];                                                                                                                       
  for(count = 1; count < MAX; count++){                                                                                                        
    sum += adarry[count];                                                                                                                      
  }                                                                                                                                            
  return sum;                                                                                                                                  
}                                                                                                                                              
                                                                                                                                                                                                                                                                                        
float subtract_arr(float subarry[]){                                                                                                           
  int count;                                                                                                                                   
  float difference = subarry[0];                                                                                                               
  for(count = 1; count < MAX; count++){                                                                                                        
    difference -= subarry[count];                                                                                                              
  }                                                                                                                                            
  return difference;                                                                                                                           
}                                                                                                                                              
                                                                                                                                                                                                                                                                                              
float multiply_arr(float multarry[]){                                                                                                          
  int count;                                                                                                                                   
  float product = multarry[0];                                                                                                                 
  for(count = 1; count < MAX; count++){                                                                                                        
    product *= multarry[count];                                                                                                                
  }                                                                                                                                            
  return product;                                                                                                                              
}