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➜ Programming
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➜ Format number to use comma in Lua?
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Format number to use comma in Lua?
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| Posted by
| Darwin
USA (125 posts) Bio
|
| Date
| Mon 17 Mar 2008 03:39 AM (UTC) |
| Message
| I was wondering if there was a simple way to format long numbers (4 or more digits) to use commas in Lua. The PiL book said to refer to a C manual, but C suggests using "%'d" which does not work in Lua.
> print(string.format("%'d", 5000))
stdin:1: invalid option '%'' to 'format'
stack traceback:
[C]: in function 'format'
stdin:1: in main chunk
[C]: ?
Any suggestions? | | Top |
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| Posted by
| David Haley
USA (3,881 posts) Bio
|
| Date
| Reply #1 on Mon 17 Mar 2008 03:48 AM (UTC) |
| Message
| input = arg[1]
input2 = string.gsub(input, "(%d)(%d%d%d)$", "%1,%2", 1)
while true do
input2, found = string.gsub(input2, "(%d)(%d%d%d),", "%1,%2,", 1)
if found == 0 then break end
end
print(input)
print(input2)
And running it:
$ lua formatter.lua 100000000
100000000
100,000,000
You need the while loop because it seems that gsub only repeats if you do left-to-right substitution, but this is more of a right-to-left substitution. |
David Haley aka Ksilyan
Head Programmer,
Legends of the Darkstone
http://david.the-haleys.org | | Top |
|
| Posted by
| David Haley
USA (3,881 posts) Bio
|
| Date
| Reply #2 on Mon 17 Mar 2008 04:03 AM (UTC) |
| Message
| | Oh, and note that %'d doesn't work because it's not in the C standard. 'man printf' indicates that many C runtime libraries are not aware of the ' specifier and will fail to handle it. Since Lua talks straight to the C library in this case, if your C library doesn't handle it then Lua won't either. (That's why Lua refers you to the C manual.) |
David Haley aka Ksilyan
Head Programmer,
Legends of the Darkstone
http://david.the-haleys.org | | Top |
|
| Posted by
| Darwin
USA (125 posts) Bio
|
| Date
| Reply #3 on Mon 17 Mar 2008 04:11 AM (UTC) |
| Message
| | Thanks, David. Works like a charm. :) | | Top |
|
| Posted by
| Nick Gammon
Australia (23,068 posts) Bio
Forum Administrator |
| Date
| Reply #4 on Mon 17 Mar 2008 04:38 AM (UTC) |
| Message
| |
| Posted by
| David Haley
USA (3,881 posts) Bio
|
| Date
| Reply #5 on Mon 17 Mar 2008 04:44 AM (UTC) |
| Message
| | Oh, heh, I didn't know about that. I'd definitely recommend Nick's version instead: it handles more cases than my quick hack does, and has good explanations of what is going on. |
David Haley aka Ksilyan
Head Programmer,
Legends of the Darkstone
http://david.the-haleys.org | | Top |
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