Thread: Function converting from 1-7 for days of the week to actual strings

Originally Posted by pankaj401

How about indexing the character array conatining day strings with the values [1...7] returned in the byte.

Code:

char days[7][]={ "Sunday", "Monday",... "Saturday" }; // You could keep this global in .text or .rodata

uByte i = ... // The byte value that you read in, assuming returns 1 to 7.

And you return

Code:

return days[i - 1];

That only works if days is a global variable; otherwise you're returning the address of a local variable, assuming that a function is returning that information.
In which case, it would be more efficient to make the function take a buffer and size, do a switch and copy the appropriate string into the buffer.

Originally Posted by Elysia

That only works if days is a global variable; otherwise you're returning the address of a local variable, assuming that a function is returning that information.
In which case, it would be more efficient to make the function take a buffer and size, do a switch and copy the appropriate string into the buffer.

Well it would be fine if this was the C++ forum, because the return type would then probably be std::string. However being C there's still nothing stopping us from doing it the preferred way, using a lookup table.

Code:

// Preconditions:
// inDayIndex is between 1 and 7
// outDayName points to a buffer big enough to hold at least 10 characters
void getDayOfWeekName(int inDayIndex, char *outDayName)
{
    static const char days[7][] =
        { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };
    strcpy(outDayName, days[inDayIndex - 1]);
}

Don't use a switch where an explicit lookup table will work.
A switch is not more efficient. It is at best just as efficient, provided it happens to optimise down to a jump table. You're better off implementing it directly as a table on your own.