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Formatting with a leading + / Lua and Perl

Archive - Originally posted on "The Horse's Mouth" - 2008-10-15 11:57:46 - Graham Ellis

In formatted printing, you can often use a leading "+" in the format string to force a positive sign to be added in front of positive numbers - for example "%+4d" means an integer, to base 10, 4 character positions as a minimum, right justified.

Here's an example of that, in code, in Lua

for john = -10, 10, 1 do
   print (string.format("xx %+4d yy",john))
end

And here is how it runs:

[trainee@easterton o8]$ lua sf

xx  -10 yy

xx   -9 yy

xx   -8 yy

xx   -7 yy

xx   -6 yy

xx   -5 yy

xx   -4 yy

xx   -3 yy

xx   -2 yy

xx   -1 yy

xx   +0 yy

xx   +1 yy

xx   +2 yy

xx   +3 yy

xx   +4 yy

xx   +5 yy

xx   +6 yy

xx   +7 yy

xx   +8 yy

xx   +9 yy

xx  +10 yy

[trainee@easterton o8]$


The same technique applies in Perl, and in other languages too.

Other leading characters:
0 - Leading zero fill
- - Left justify