Basic Functions
assert(condition[, cessage])
collectgarbage ([limit])
dofile(filename)
error( message[, level] )
gcinfo()
_G
getfenv (f)
ipairs (table)
loadfile(filename)
loadstring (string [, chunkname])
next(table[, index])
pairs (table)
pcall (myFunction, parameter1, oarameter2, ...)
print (e1, e2, ...)
rawequal (v1, v2)
rawget (table, index)
rawset (table, index, value)
require (packagename)
setfenv (f, table)
setmetatable (table, metatable)
tonumber (e [, base])
tostring (e)
type( variable )
unpack (list)
_VERSION
xpcall (f, err)
assert(condition[, message])As soon as the condition will be false or nil, the programm will be stopped and returns the message.
The message is like:
filename:lineNo:message
Stack traceback:
Afterwards we get information where the problem is located.
example:
assert( 1 == 2, "That is wrong" )
--> filename:lineNo:That is wrong
The garbage collector.
As the name already tells, with this function the garbage collector of the programm can be started. The limit specifies the size of the reserved memory of the cargabe collector.
The garbage collector is cleaning the memory of occupied space. To specify the limit is optional. If no limit is specified, the function takes 0.
Example:
print( gcinfo()) --> 17 29
bigString = string.rep('a', 100000) -- a lot of memory will be used
print( gcinfo()) --> 322 197
collectgarbage (10000)
print( gcinfo()) --> 163 10000 apparently it has not been used as much memory as we thought. The limit is set to 10000.
collectgarbage (5)
print( gcinfo()) --> 139 279 something has been found, so the limit of 5 we set, seems to be too small.
bigString = nil -- the value of bigString is not available anymore. We have been deleted it.
collectgarbage ()
print( gcinfo()) --> 29 59
!!!!!!!!! Since lua 5.1 collectgarbage("count") has been replaced the function gcinfo() !!!!!!!!!!
Opens the file named dateiName and is executing it at Lua-code.
Return: what the file is returning as result of file code.
With this function we will be able to split our project into any separate files. It seems as it has been writen in one pour.
Example:
File 1 (Unit1.lua)
return "I am File 1"
File 2 (Unit2.lua) <-- wird ausgeführt
print( dofile("Unit1.lua") ) --> I am File 1
The function error returns the bug which has been produced by the last executed code in subject to the value of level and aborts the programm.
To explain the parameter level I will show you the following function:
1 function IFoundTheBug()
2 a = ""
3 print( a..b ) -- b is nil therefore error
4 end
5
6 function myError()
7 _, cError = pcall(IFoundTheBug) -- at this line the function will be executed with pcall (protected)
8 end
9
10 function Call_1()
11 error(cError,1) -- Error-message will be returned and the programm will be aborted.
12 end
13
14 function Call_2() -- a kind of intermediate station
15 Call_1()
16 end
17 myError() -- call of function, that creates the error in a protected environment
18
19 Call_2() -- call of function that returns the error by using the intermediate station
What happens?
- All functions will be imported / read in.
- The function myError will be executed.
- This calls in a protected environment the function IFoundTheBug by using pcall.
- By using pcall the error-message will not be return directly.
- The message will be stored in cError.
- Then the function Call_2 will be executed.
- This starts Call_1
- The function Call_1 returns cError dependent on level.
level = 0 --> the error/bug will be returned promptly.
level = 1 --> a level before
level = 2 --> again a level before
level = 3 --> 3 levels before
This function returns 2 values.
- The first : the value of used memory.
- The second: the value, of the reserved memory for the garbage collector.
Both values are in kB.
!!!!!!!!! Since lua 5.1 collectgarbage("count") has been replaced this function !!!!!!!!!!
Example:
print( gcinfo()) --> 17 29
bigString = string.rep('a', 100000) -- a lot of memory will be used
print( gcinfo()) --> 322 197
The function next returns index after index and each associated value of table in an unsorted way. At index == nil next returns the first index. If the last index will be reached, next returns nil.
Example:
Felt(Adapted) function inext:
function inext(_table, _index)
_index = next(_table, _index)
if _index then
if type(_index) ~= "number" then
repeat
_index = next(_table, _index)
if type ( _index) == "number" then
break
end
until not _index
end
end
return _index
end
The only task of the function pairs is, to execute the function next and to return the according table.
myFunc, myTable = pairs( table )
myFunc includes the function next
and in myTable the returned table.
We can find this in the generic for-loop
The only task of the function ipairs is like next and to return the according table.
Supposed the function inext would exist (similar to the function next at pairs) and it would return following:
myFunc, myTable = ipairs( table )
Now there is a function existing in myFunc similiar to next. However, it only returns its next numerical index and returns the assigned table to myTable.
We can find this in the generic for-loop
Opens the file filename and executes it, but not as Lua-code.
Returns 2 values:
- the compiled file as function. (in case of an error nil)
- the error-message (if existing, otherweise nil)
loadedFunction, cError = loadfile("filename.lua")
- if loadedFunction == nil --> an error occurs. The message-text will be in cError.
- Otherwise, the compiled file will be in loadedFunction as function.
The function pcall executes the function myFunction with the according parameters.
The difference to the regular call: It will not be responded directly on an error.
The function returns following:
- all passed in the right way --> true / error --> false
- followed by the values that the function returns. In case of an error an according error-message appears.
Example:
The programm aborts and you will receive the error-message.
Gets the real value of table[index], without invoking any metamethod.
Parameter:
- The table with the according value
- The index in the according table. (This can be any valid value except nil)
result = rawget (myTable, 5)
Can be compared with
result = myTable[5]
Sets the value of table[index], without invoking any metamethod.
Parameter:
- The table where a value has to be set
- The index in that table. (This can be any valid value except nil)
rawget (myTable, 5, true)
Can be compared with
myTable[5] = true
Changes the variable into a number to the base of 10 logarithm. If this will not succeed the result is nil.
Parameter:
- A value ( number or string )
- The base, which should be considered (optional: default is 10)
Can be explained best of all with an example:
print(tonumber("55")) --> 55
print(tonumber(55)) --> 55
print(tonumber("55a")) --> nil
print(tonumber(10101.1012e12)) --> 1.01011012e+16
print(tonumber("100110"), 2) --> 38
print(tonumber("100112"), 2) --> nil
print(tonumber("LUA"), 36) --> 28306
This function returns a string with a type of an variable.
As parameters we have to give over following:
- The variable that has to be checked and the value that should be assigned.
type (variable)
possibel returns:
"nil, "number", "string", "boolean, "table", "function", "thread", und "userdata".
Example:
result = type (5)
--> resultat == "number"
myVar = "This is a sentence"
result = type ( myVar )
--> result == "string"
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Copyright © Robert Schmitz 2006
Copyright © Robert Schmitz 2006