I'm trying to write a program that uses a function to calculate a water bill. It reads the information about water usage from a file, then calculates the water bill after tax.
This is the file:
g 5000
B 1250
M 50
This is what the output should be:
Type Water usage Cost including tax($)
g 5000 194.30
B 1250 93.89
Wrong user type
This is my output:
Type Water usage Cost including taxWrong user type.
g 5000 0.000000
B 1250 18.750750
Wrong user type.
I'm not sure if the problem lies in my formula or something else. There's obviously a problem with the if else statement in the function since it keeps printing "Wrong user type" where it shouldn't.
This is my code:
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <math.h>
double water_billcalculation(char user_type, double water_use, double bft, double at);
int main(void) {
FILE* water;
water = fopen("water_usage.txt", "r");
char user_type;
int cf;
double bft = 0, at = 0, water_use = 0;
printf("Type Water usage Cost including tax");
while (fscanf(water, "%c%d ", &user_type, &cf) != EOF) {
//water_billcalculation(user_type, water_use, bft, at);
printf("%c %d %lf\n", user_type, cf, water_billcalculation(user_type, water_use, bft, at));
}
return(0);
}
double water_billcalculation(char user_type, double water_use, double bft, double at) {
if (user_type == 'G') {
bft = (water_use * 0.035) 3.75;
at = bft (bft * .087);
}
else if (user_type == 'B') {
bft = (water_use * .0553) 17.25;
at = bft (bft * .087);
}
else if (user_type == 'R') {
if (water_use <= 400) {
bft = (water_use * .04) 13.5;
at = bft (bft * .087);
}
else if (water_use > 400 && water_use <= 700) {
bft = (water_use * .062) 13.5;
at = bft (bft * .087);
}
else {
bft = (water_use * .12) 13.5;
at = bft (bft * .087);
}
}
else {
printf("Wrong user type.\n");
}
return(at);
}
CodePudding user response：
The problem
You're "reading" your file in a wrong way. Change this line:
while (fscanf(water, "%c%d ", &user_type, &cf) != EOF) {
to this (notice the difference in the second argument of fsanf):
while (fscanf(water, " %c%d", &user_type, &cf) == 2) {
Also your water_billcalculation is wrong: You're looking after the user_type G, B and R according to your code, but you're actually looking after g, B and M!
So you'd need to change this part:
if (user_type == 'G') {
bft = (water_use * 0.035) 3.75;
at = bft (bft * .087);
}
else if (user_type == 'B') {
bft = (water_use * .0553) 17.25;
at = bft (bft * .087);
}
else if (user_type == 'R') {
to this:
if (user_type == 'g') {
bft = (water_use * 0.035) 3.75;
at = bft (bft * .087);
}
else if (user_type == 'B') {
bft = (water_use * .0553) 17.25;
at = bft (bft * .087);
} else if (user_type == 'M') {
After this, you'll get the following output:
Type Water usage Cost including taxg 5000 4.076250
B 1250 18.750750
M 50 14.674500
I'm a little bit unsure, if this is your desired output, because according to your post which says, that you'd like to have this output:
Type Water usage Cost including tax($)
g 5000 194.30
B 1250 93.89
Wrong user type
makes me thinking that:
- You actually don't want to "parse" the type
M. If yes, remove theelse if (user_type == 'M')condition in thewater_billcalculationfunction. - The calculation isn't correct or I don't see another bug in my code (althought I even ran it with valgrind, which didn't complain about any invalid actions).
Code review
Some improvement ideas came up in my mind, when I read your code. So here are some suggestions. You can skip this, if you aren't interested in them.
Check the return value after calling fopen!
fopen returns you a FILE * but only IF everything worked fine! So please make sure to add a lookup part:
FILE * water;
water = fopen("water_usage.txt", "r");
if (water == NULL) {
// Thanks to @William Pursell for pointing out to use stderr for error messages, I forget that pretty often
perror("Houston, we've got a problem: The file couldn't be opened :(\n");
// or use the `exit()` function here (but you'd need to include stdlib.h)
return 1;
}
String formatting
I'd recommend to use \t instead of counting your spaces. This would let you produce a better output. Also don't forget to add a \n if you're printing something in a new context.
In the beginning when I've got this ouptut:
Type Water usage Cost including taxg 5000 4.076250
B 1250 18.750750
M 50 14.674500
I was a little bit irritated first, because I didn't saw the line with the g type.
Change your output to the following:
printf("Type\tWater usage\tCost including tax\n");
while (fscanf(water, "%c %d\n\n", &user_type, &cf) != EOF) {
printf("%c\t%d\t\t%lf\n", user_type, cf, water_billcalculation(user_type, water_use, bft, at));
}
This gives me the following output:
Type Water usage Cost including tax
g 5000 4.076250
B 1250 18.750750
M 50 0.000000
which is better to read (in my opinion).
(Optional) use switch-case
Your water_billicalculation could include a switch-case statement instead of nested if-else statements.
I'd have the written the function as follows:
double water_billcalculation(char user_type, double water_use, double bft, double at) {
switch (user_type) {
case 'g':
bft = (water_use * 0.035) 3.75;
at = bft (bft * .087);
break;
case 'B':
bft = (water_use * .0553) 17.25;
at = bft (bft * .087);
break;
case 'M':
if (water_use <= 400) {
bft = (water_use * .04) 13.5;
at = bft (bft * .087);
}
else if (water_use > 400 && water_use <= 700) {
bft = (water_use * .062) 13.5;
at = bft (bft * .087);
}
else {
bft = (water_use * .12) 13.5;
at = bft (bft * .087);
}
break;
defaut:
fprintf(stderr, "Wrong user type: '%c'\n", user_type);
break;
}
return at;
}
instead of this:
if (user_type == 'g') {
bft = (water_use * 0.035) 3.75;
at = bft (bft * .087);
}
else if (user_type == 'B') {
bft = (water_use * .0553) 17.25;
at = bft (bft * .087);
}
else if (user_type == 'M') {
// and so on...
but that's probably very individual, so see this as an opinion please.
CodePudding user response：
While @TornaxO7 answered your literal question, you would have been able to easily determine what the problem is by debugging your program:
Specifically,
- By stepping your program or breaking after the scan, you would have noticed what values you're getting in
user_typeand incf. - By stepping through the comparisons in
water_billcalculation(), you would have noticed how comparisons you expected to succeed, fail - which would have led you to notice you're comparing'g'with'G'.
Additionally, or alternatively, adding some "debug-prints" or log-type printing to your program, at least while developing it, provides some of the same information even in regular runs without debugging.