error: invalid operands to binary + (have ‘float’ and ‘float *’)

Question

I'm trying to make a program in which I can read a file with animals weight and calculate the weight average. I got this error while trying to compile. Does anyone knows why?

funciones.c

#include "header.h"

float count_animals(FILE *file){

        float total_animals = 0;
        char word[20];

        while (fscanf(file, "%s", word) == 1){

                total_animals++;

        }

        return total_animals;

}

float sum_weight_animals(FILE *file){

        float sum_weight = 0;
        float weight[20];

        while (fscanf(file, "%f", weight) == 1){

                sum_weight += weight;

        }

        return sum_weight;

}

header.h

#include <stdio.h>

#define MAXWORD 80

float count_animals(FILE *file);

float sum_weight_animals(FILE *file);

Just in case here's the main.c Now I have the problem that it's not adding up the sum_weight value in sum_weight_animals function.

#include "header.h"

int main(){

        char WORD[MAXWORD];
        char file_name[MAXWORD];
        FILE *fileptr;

        printf("Please, enter a file name: ");
        scanf("%s", file_name);

        printf("Reading file %s...\n", file_name);
        fileptr = fopen(file_name, "r");

        if(fileptr == NULL){

                fprintf(stderr, "ERROR: The file '%s' doesn't exists\n", file_name);
                return 1;

        }

        float total_animals = count_animals(fileptr);

        if (total_animals > 0){

                printf("There're %.2f animals.\n", total_animals);

        }
        else{

                fprintf(stderr, "WARNING: File not found or it's empty\n");

        }



        float total_sum = sum_weight_animals(fileptr);

        if (total_sum > 0){

                printf("The sum of all animal's weight is %.2f [kg].\n", total_sum);

        }
        else{

                fprintf(stderr,"WARNING: File not found or it's empty\n");

        }


        fclose(fileptr);

        return 0;

}

When ex Makefile, it compiles correctly and the first function works fine, but the second one doesn't and it gives me the WARNING: File not found or it's empty\n that I put on main.c

Answer 1

Replace

float weight[20];

with

float weight;

and replace

fscanf(file, "%f", weight)

with

fscanf(file, "%f", &weight)

---

Explanation:

sum_weight += weight;

is basically equivalent to

sum_weight = sum_weight + weight;

Let's look at the right-hand side, sum_weight + weight.

• sum_weight is a float.
  
• weight is an array of 20 float elements.

What does it mean to add a float and an array together? Nothing, that's what. This makes no sense.

You assigned a value to weight[0], and this is the value you want to add. Not weight.

But why is weight an array in the first place? As the name implies, it's only used to store one weight. You only ever assign to weight[0]. So it makes no sense to use an array.