C program cannot show the output

Question

My C program does not show the output.

My code in the C language:

int x = 0; // Installment
int y = 0  // Balance

for (i=1; i<=installment;i++)
        {
            printf("%d %d %d\n", i, x=totalFee/installment, y = totalFee-(totalFee/instalment));
        }

Correct output:

Total fees: 300
Month  Installment  Balance
  1      100          200
  2      100          100
  3      100            0

My output:

Total fees: 300
Month  Installment  Balance
  1      100          200
  2      100          200
  3      100          200

This is just part of the code. Because this is the part where I have an issue. Other parts are fine.

It is weird to expect different outputs with a loop that print always same values.... I mean `totalFee`, `installment` and `x` are constants inside the loop so.... — LPs, Nov 07 '16 at 07:38
And fyi, you can *not* assume the evaluation+assignment for `x` happens before `y` in your function call. [Order of parameter eval is not guaranteed](https://stackoverflow.com/questions/21600108/c-function-parameters-order-of-evaluation). — WhozCraig, Nov 07 '16 at 07:39
`int y = 0` does not terminate with a semicolon. `installment` is not defined. `totalFee` is not defined. — siavashk, Nov 07 '16 at 07:41
If I change the for loop into the below: for (i=1; i<=installment;i++) { printf("%d %d %d\n", i, x=totalFee/installment, y = totalFee-(totalFee/installment,)); } — Addison, Nov 07 '16 at 07:41
With the new edit, neither the question nor any of the posted answers make any sense. Voting to close this as unclear. — Lundin, Nov 07 '16 at 07:46

score 2 · Answer 1 · edited May 23 '17 at 10:27

2

Try this:

for (i=1; i<=installment;i++)
{
    x = totalFee/installment;
    y = totalFee-x;
    printf("%d %d %d\n", i, x, y);
}

In C/C++, the compiler decides in which order it evaluates the parameters when a function is called. There is absolutely no guarantee that the order will be from first to last parameter. So most likely it evaluated totalFee-x before x = totalFee/installment which is not what you expected.

See Compilers and argument order of evaluation in C++ or Order of evaluation in C++ function parameters or even function parameter evaluation order. Specially, check this answer.

Now you updated your post and replaced by y = totalFee-x by y = totalFee-(totalFee/instalment). This last one should work as y assignment does not rely on x. If it does not work for you, it's just that you are doing your operations the wrong way. Use a debugger to see what's going on.

edited May 23 '17 at 10:27

Community

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answered Nov 07 '16 at 07:41

jpo38

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Bro, Thanks for your reply. But the output still the same as the balance still cant deduct. – Addison Nov 07 '16 at 07:45
Also from what the asker says, he probably wants x = x * i inserted after the initialisation of x. – Nonanon Nov 07 '16 at 07:45
Actually I just wan my "y" to be deducted. Thanks for your reply. – Addison Nov 07 '16 at 07:46

score 1 · Answer 2 · answered Nov 07 '16 at 07:41

The problem is likely related to order of evaluation of function parameters. You cannot know or assume that x=totalFee/installment is executed before y = totalFee-x. Also, it is generally bad practice to use assignment inside expressions.

Try to change your loop body to:

x = totalFee/installment;
y = totalFee-x;
printf("%d %d %d\n", i, x, y);

score 0 · Answer 3 · answered Nov 07 '16 at 07:45

0

maybe you don`t understand your loop

let`s step it.

First, i = 1, x = 300/3 = 100, y = 300 - 100 = 200

Second, i = 2, x= 300/3 = 100, y = 300 - 100 = 200

third, i = 2, x= 300/3 = 100, y = 300 - 100 = 200

the x you make it 100

answered Nov 07 '16 at 07:45

Xiangxuan Qu

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You can't assume that the loop gets executed this way. – Lundin Nov 07 '16 at 07:50
OK.. Thanks a lot – Addison Nov 07 '16 at 08:11

Lineesh K Mohan · Answer 4 · 2016-11-07T08:57:15.760

0

The program for your required output

for (i=1; i<=installment;i++)
{
    x = totalFee/installment;
    y = totalFee-(x * i);
    printf("%d %d %d\n", i, x, y);
}

edited Nov 07 '16 at 08:57

answered Nov 07 '16 at 07:51

Lineesh K Mohan

1,702
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Thanks for all help.. I really appreciate it. May God bless u all. – Addison Nov 07 '16 at 08:11

C program cannot show the output

4 Answers4