mismatched comparison error in XC8

[ep.hobbyiest]

i m getting error in in XC8 compiler in if condition.
the error as

mismatched comparison

and the condition

            digit[0]--;
            if(digit[0] == 0-1)
                digit[0] = 9;

what is the error then.

 

[horace1]

1. what is the data type of digit
2. what do you intend by the expression 0-1?
arithemtic expression 0 - 1 ? if so its value is -1
0 or 1 ?

 

[ep.hobbyiest]

Declaration is as

char digit[4]={0};

i want to compare value of -1.

i use such expression but i don't why it is giving error now.

 

[horace1]

XC8 probably defaults type char to unsigned char hence the mismatched comparison warning

as you are going to compare it with -1 try defining digit as a signed char

signed char digit[4]={0};

general advice is if one is using a char to hold data explicitly define it as signed char (range 0-255) or unsigned char (range -128 to +127) as required