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
(written 2008-10-15)

 U110 - Lua - Input / Output
  [1744] Lua examples, Lua Courses - (2008-08-08)
  [2344] Reading a data file and sensing EOF in Lua - (2009-08-10)
  [3558] Python or Lua - which should I use / learn? - (2011-12-21)

P207 - Perl - File Handling
  [12] How many people in a room? - (2004-08-12)
  [114] Relative or absolute milkman - (2004-11-10)
  [255] STDIN, STDOUT, STDERR and DATA - Perl file handles - (2005-03-23)
  [616] printf - a flawed but useful function - (2006-02-22)
  [618] Perl - its up to YOU to check your file opened - (2006-02-23)
  [702] Iterators - expressions tha change each time you call them - (2006-04-27)
  [867] Being sure to be positive in Perl - (2006-09-15)
  [1312] Some one line Perl tips and techniques - (2007-08-21)
  [1416] Good, steady, simple example - Perl file handling - (2007-10-30)
  [1442] Reading a file multiple times - file pointers - (2007-11-23)
  [1467] stdout v stderr (Tcl, Perl, Shell) - (2007-12-10)
  [1709] There is more that one way - Perl - (2008-07-14)
  [1860] Seven new intermediate Perl examples - (2008-10-30)
  [1861] Reactive (dynamic) formatting in Perl - (2008-10-31)
  [2233] Transforming data in Perl using lists of lists and hashes of hashes - (2009-06-12)
  [2405] But I am reading from a file - no need to prompt (Perl) - (2009-09-14)
  [2818] File open and read in Perl - modernisation - (2010-06-19)
  [2821] Chancellor George Osborne inspires Perl Program - (2010-06-22)
  [2833] Fresh Perl Teaching Examples - part 2 of 3 - (2010-06-27)
  [3326] Finding your big files in Perl - design considerations beyond the course environment - (2011-06-14)
  [3548] Dark mornings, dog update, and Python and Lua courses before Christmas - (2011-12-10)
  [3830] Traversing a directory in Perl - (2012-08-08)
  [3839] Spraying data from one incoming to series of outgoing files in Perl - (2012-08-15)

Back to Validating Credit Card Numbers

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Forward to Lua Course, and the Wiltshire Countryside too

Passing a table from Lua into C
Calling functions in C from your Lua script - a first HowTo
How many cups of coffee?
Lua Course, and the Wiltshire Countryside too
Formatting with a leading + / Lua and Perl
Validating Credit Card Numbers
Job application
Oxford in Pictures
Alfred the Great
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