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➜ MUSHclient
➜ Lua
➜ Defining global variables
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Defining global variables
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| Posted by
| Gore
(207 posts) Bio
|
| Date
| Reply #15 on Tue 16 Jan 2007 02:52 PM (UTC) |
| Message
| Style wise: which is a better way to see if a variable is true?
if variable == 1 then
--blah
end
or
if variable then
--blah
end
? | | Top |
|
| Posted by
| David Haley
USA (3,881 posts) Bio
|
| Date
| Reply #16 on Tue 16 Jan 2007 03:28 PM (UTC) |
| Message
| The second one is probably better of those two. For the first, you should test against true, not one. Otherwise, you have to worry about it being 2, 3, 4, and so forth. (Lua has the boolean type, so it should be used.)
The second case will be true unless the variable is nil or false.
Come to think of it, if the variable is 0, it will be true as well, which might or might not be what you want.
Testing against 'true' is probably what you want, really. And if you're not testing against a boolean, then you should have whatever test you are looking for, e.g. if var > 0 or whatever.
Stylistically it's generally better to make explicit conditions just so it's clear what's going on. |
David Haley aka Ksilyan
Head Programmer,
Legends of the Darkstone
http://david.the-haleys.org | | Top |
|
| Posted by
| Nick Gammon
Australia (23,140 posts) Bio
Forum Administrator |
| Date
| Reply #17 on Sat 20 Jan 2007 03:35 AM (UTC) |
| Message
| I don't like:
if variable == true then
The "if" test is already checking if the expression is true or not, and thus it is like saying "if this is true is true".
Quote:
Lua has the boolean types ...
This is true, however Lua values can have boolean types, Lua variables are untyped. Thus you can't make a variable a boolean, it just might happen to contain a boolean value at a certain time.
A variable might in fact contain nil (which would be considered false in an "if" statement), or true or false.
Only two value are considered false in an "if" test: nil and false. Anything else is true, including numeric zero.
I certainly wouldn't say:
if variable == 1 then
The implication is that a value of 0 is false, whereas 0 is still considered true.
Of course, you could write:
if variable == 0 then
-- this is the false branch
end -- if
But I think that is rather convoluted. |
- Nick Gammon
www.gammon.com.au, www.mushclient.com | | Top |
|
| Posted by
| Nick Gammon
Australia (23,140 posts) Bio
Forum Administrator |
| Date
| Reply #18 on Sat 20 Jan 2007 03:51 AM (UTC) |
| Message
| In case I haven't made myself clear in the above post:
- I would use the boolean type (ie. true or false) rather than 0/1
- I would say:
if variable then ...
... rather then "if x == true" or "if x == 1"
- In extreme cases you could use the value nil to indicate "I don't know if it is true or false". However otherwise, uninitialized variables will default to nil, which is effectively false.
|
- Nick Gammon
www.gammon.com.au, www.mushclient.com | | Top |
|
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