Question

I want to implement a text drawing function. But I am not sure how \t works, which means I don’t know how many spaces I should print for \t.

I have come up with the following algorithm:

a) Each \t represents at most NUMBER_OF_SPACES_FOR_TAB spaces.
b) If \t appears in the last line at a corresponding position, \t for this line should be aligned to the \t of last line.

Example:

printf("a\t\tb\n");
printf("\t\tc\n");

Should print:

a11112222b
34444c

Where:

1.Number i represents the spaces of \t at position i

2.NUMBER_OF_SPACES_FOR_TAB == 4

Does anyone know the standard algorithm? Thanks in advance.

Answer 1

A tab character should advance to the next tab stop. Historically tab stops were every 8th character, although smaller values are in common use today and most editors can be configured.

I would expect your output to look like the following:

123456789
a       b
        c

The algorithm is to start a column count at zero, then increment it for each character output. When you get to a tab, output n-(c%n) spaces where c is the column number (zero based) and n is the tab spacing.