Arduino switch case multiple variables12/2/2023 Here's yet another implementation of a "switch" statement. This version uses the function switch(table) to add a method case(table,caseVariable) to a table passed to it. It allows for arguments to be put in formatted. This method is close to Python's eval() method and it's nice looking. Here's a neat and compact version using the loadstring() function and calling each element in a table of cases. Usage (Note, that in the following example you can also pass parameters to the function called) :. = function (x) print( math.random()) end, This is very efficient in Lua since tables are hashed by key value which avoids repetitive if then. Some are the below solutions are more for syntactic sugar or proof-of-concept rather than recommended practices.Ī simple version of a switch statement can be implemented using a table to map the case value to an action. The above is a practical solution that is the basis for the more elaborate approaches given below. We might address that with this minor change: This improves performance but has the side-effect of moving the lookup table further from its usage. Note how the table construction was placed outside the block to avoid recreating the table for each use (table constructions cause heap allocations). = function() return is_canadian and "eh" or "" endįor _,v in ipairs(letters) do local s = type(t) = "function" and t() or t or "blah" print(s)Ĭ compilers can optimize the switch statement in a roughly similar way via what is called a jump table, at least under suitable conditions. Z = function() return is_canadian and "zed" or "zee" end, If we rewrite this as a lookup table, the code can run in linear-time, O(M), and without the redundancy so that the logic is easier to modify at whim: These concerns (minor as they may be) have been noted elsewhere as well ( ). A more minor concern is the syntax redundancy of having " v =" for each test. If the number of elements in letters is M and the number of tests is N, then the complexity is O(M*N), or potentially quadratic. When there are many tests as such, the comparison chain is not always the most efficient. Local is_canadian = false function sayit(letters)įor _,v in ipairs(letters) do if v = "a" then print( "aah")Įlseif v = "z" then print(is_canadian and "zed" or "zee")Įlseif v = "?" then print(is_canadian and "eh" or "") The first question to ask is why we might want a switch statement rather than a comparison chain as such: There are ways to emulate the same effect as discussed here. This issue has come up a number of times on the mailing list. Lua-users wiki: Switch Statement Switch Statement
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |