11/29/2023 0 Comments Return value in switch case java![]() 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. Switch expression is a new form of traditional switch statement where case statements are followed by an arrow instead of a colon as shown below.Lua-users wiki: Switch Statement Switch Statement If a single case statment should match multiple values, then it needs to be repeated for each label as shown in the previous example. It would be better if the case block would be able to assign this value directly to the variable without writing it again and again. If any break is accidentally missed, leads to unexpected errors and fall through(meaning that a case block below the matched case executes).Ĭonside the below switch statement String size = "S" Įach case block in the above switch statement initializes/modifies the value of a variable and the variable needs to be written again and again. Traditional switch, also referred as switch statement, requires break statement after every case block as shown highlighted below. If you are not familiar with switch statement, then go through this article.įirst, we shall look at the problems in the traditional switch and how switch expression addresses the solution to these. Switch expression is a new feature that was added in java 12 to address some problems in traditional switch statement.
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