Add util.In( any thing, vararg values ) #2056
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Allows you to check if `thing` is among `values`.
Using the function, we can do this:
```lua
local myUsergroup = 'user'
if util.In( curState, 'user', 'vip' ) then
-- ...
end
```
... instead of:
```lua
local allowedUsergroups = {
user = true,
vip = true,
}
local myUsergroup = 'user'
if allowedUsergroups[ myUsergroup ] then
-- ...
end
```
Of course, the second code is faster because it performs a key lookup (which is O(1) vs. my O(n) implementation), but `util.In` is useful in contexts where performance is not so important
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Bad naming aside, I understand this is less efficient than the proposed method, but by your own admission that is not the focus here. |
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Not creating the table would indeed be much more efficient when JIT compiles the select calls. Not as efficient as creating a hashtable with true vals, but for dynamic vararg values, this seems like the best solution. Efficiency should be the focus of this addition. |
| @@ -408,3 +408,15 @@ function util.IsBinaryModuleInstalled( name ) | |||
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| return false | |||
| end | |||
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| function util.In( thing, ... ) | |||
| for i = 1, select( '#', ... ) do | |||
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nit: I think it was Spar who demonstrated that localizing your for limit makes it marginally faster.
Something like:
| for i = 1, select( '#', ... ) do | |
| local limit = select( "#", ... ) | |
| for i = 1, limit do |
might be a nice microoptimization
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I don't see how this is an improvement since the loop limit is only evaluated once.
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I don't see how this is an improvement since the loop limit is only evaluated once.
Does it behave like that in GLua too?
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Not sure how I can improve on my solution ( except for brandonsturgeon's suggestion). Of course, pretty much the same thing can be done using Regarding the function name - I was guided by Python syntax: if thing in (a, b, c):
# ... |
Yes, performance is not a focus, because in that case I will use a key lookup. However, the developed solution, although similar to |
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With regards to the name, |
util.In:
sum = 0.286
avg = 0.00286
median = 0.0030000000000001
util.In2:
sum = 0.0020000000000024
avg = 2.0000000000024e-05
median = 0function util.In2( thing, ... )
local iMax, i = select( '#', ... ), 1
::iter::
if thing == select( i, ... ) then
return true
end
i = i + 1
if i <= iMax then goto iter end
return false
end |
Sample size and size of |
lib: https://github.com/Be1zebub/Small-GLua-Things/blob/master/sh_benchmark.lua util.In:
sum = 0.035
avg = 0.00035
median = 0
util.In2:
sum = 0.00099999999999767
avg = 9.9999999999767e-06
median = 0
benchmark("util.In", function()
a = util.In(userName, "admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", userName)
end, 1000, 100)
benchmark("util.In2", function()
a = util.In2(userName, "admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "admin", "test", "user", "admin", "test", "user", "admin", "test", "user","admin", "test", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", "user", userName)
end, 1000, 100)table unpack util.In:
sum = 0.113
avg = 0.00113
median = 0.0010000000000048
util.In2:
sum = 6.415
avg = 0.06415
median = 0.063000000000017
local a = false
local users = {}
local userName = "superadmin"
for i = 1, 253 do
if i % 2 == 0 then
users[i] = "admin"
else
users[i] = "user"
end
end
users[254] = 'superadmin'
benchmark("util.In", function()
a = util.In(userName, unpack(users))
end, 1000, 100)
benchmark("util.In2", function()
a = util.In2(userName, unpack(users))
end, 1000, 100) |
Allows you to check if
thingis amongvalues.Using the function, we can do this:
... instead of:
... or:
Of course, the second code is faster because it performs a key lookup (which is O(1) vs. my O(n) implementation), but
util.Inis useful in contexts where performance is not so important