C2106: '=' : left operand must be l-value

Question

So, I'm learning C as my first language and as doing some coding for practise I got the error above. I done everything as the book says (Stephen G. Kochan: Programming in C, Third Edition). What am I doing wrong? I'm using Microsoft Visual Studio 2015.

Thanks for your help! Mark

struct date
{
int month;
int day;
int year;
};

int main(void)
{
    struct date today, tomorrow;
    int numberOfDays(struct date d);

    printf("Adja meg a mai datumot (hh nn eeee): ");
    scanf_s("%i%i%i", &today.month, &today.day, &today.year);

    if (today.day != numberOfDays(today))
    {
        tomorrow.day = today.day + 1;
        tomorrow.month = today.month;
        tomorrow.year = today.year;
    }
    else if (today.month == 12)
    {
        tomorrow.day = 1;
        tomorrow.month = 1;
        tomorrow.year = today.year + 1;
    }
    else
    {
        tomorrow.day = 1;
        tomorrow.month = today.month + 1;
        tomorrow.year = today.year;
    }
    printf("A holnapi datum: %i/%i/%.2i.\n", tomorrow.month, tomorrow.day, tomorrow.year % 100);

    return 0;
}

int numberOfDays(struct date d)
{
    int days;
    bool isLeapYear(struct date d);
    const int daysPerMonth[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

    if (isLeapYear(d) == true && d.month == 2)
        days = 29;
    else
        days = daysPerMonth[d.month - 1];

    return days;
}

bool isLeapYear(struct date d)
{
    bool leapYearFlag;

    if ( (d.year % 4 == 0 && d.year % 100 = 0) || d.year % 400 == 00) //The error shows up here
        leapYearFlag = true;
    else
        leapYearFlag = false;

    return leapYearFlag;
}

Try a simpler program first. As you build it up step by step, you'll either discover your error or a better question. — Kerrek SB, Jan 18 '17 at 18:57
Kerrek: I done it that way. This is the 9th chapter in the book. Lashane: Thanks! Sadly the error still occurs. — Márk Burka, Jan 18 '17 at 19:24

Vlad from Moscow · Answer 1 · 2017-01-18T19:10:57.237

1

Here is a typo

if ( (d.year % 4 == 0 && d.year % 100 = 0) || d.year % 400 == 00) 
                                    ^^^^

I think you mean

if ( (d.year % 4 == 0 && d.year % 100 != 0) || d.year % 400 == 00) 
                                     ^^^^

And 00 is equivalent to 0.:)

The function can be written simpler

bool isLeapYear( struct date d )
{
    return ( d.year % 4 == 0 && d.year % 100 != 0 ) || ( d.year % 400 == 0 );
}

edited Jan 18 '17 at 19:10

answered Jan 18 '17 at 19:02

Vlad from Moscow

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Thank you. Yes those were typos. Sadly the error still occurs. – Márk Burka Jan 18 '17 at 19:26
@MárkBurka I do not see any other compilation error. – Vlad from Moscow Jan 18 '17 at 19:38
Yeah. Well, thanks anyway! – Márk Burka Jan 19 '17 at 17:59

C2106: '=' : left operand must be l-value

1 Answers1