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Commit faa44ef

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overloading: Lua (version 2)
1 parent a85fcc6 commit faa44ef

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3 files changed

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‎book/cite.bib‎

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@@ -586,4 +586,13 @@ @online{2009-bailey
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url = {https://stackoverflow.com/a/1734905},
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urldate = {Oct 6, 2009},
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organization = {stackoverflow.com},
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}
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@online{2011-berteig,
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author = {{RBerteig of stackoverflow}},
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title = {Variable number of function arguments Lua 5.1},
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year = {2011},
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url = {https://stackoverflow.com/a/7630202},
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urldate = {Oct 3, 2011},
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organization = {stackoverflow.com},
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}

‎book/polymorphism.tex‎

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@@ -481,11 +481,14 @@ \subsection{Javascript}
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\subsection{Lua}
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Lua does not support method overloading.
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A similar behavior can be achieved by testing arguments number and types.
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A similar behavior can be achieved by using a \nameword{variadic function} and testing arguments number and types.
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You can select a parameter using the function \keyword[Lua]{select} \citep{2011-berteig}.
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The same function can be used to know te number of parameters.
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\lstinputlisting[language={[KB]Lua}, linerange={2-19,35-37}, style=codeStyle]{../codes/lua/polymorphism/overloading.lua}
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\lstinputlisting[language={[KB]Lua}, linerange={2-20,37-39}, style=codeStyle]{../codes/lua/polymorphism/overloading.lua}
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Subclasses can define the same method, verify the arguments for new definitions and delegate the control to the super's methods.
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If you do not want to use \keyword[Lua]{select}, you can put the arguments in a list and access the parameters as list members.
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\lstinputlisting[language={[KB]Lua}, linerange={22-32,40-43}, style=codeStyle]{../codes/lua/polymorphism/overloading.lua}
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@@ -502,6 +505,10 @@ \subsection{Perl}
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\lstinputlisting[language={[KB]Perl}, linerange={13-25,34-37}, style=codeStyle]{../codes/perl/polymorphism/overloading.pl}
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\subsection{PHP}
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PHP does not support method overloading; Overloading in PHP is entirely a different thing.
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\section{Methods overriding}
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‎codes/lua/polymorphism/overloading.lua‎

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@@ -8,8 +8,9 @@ function Person:new() -- The constructor
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return instance
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end
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function Person:read(arg1)
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if not arg1 then
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function Person:read(...)
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local arg1 = select(1, ...)
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if not arg1 then -- select("#", ...) for parameters number
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print("I am reading")
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else
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if type(arg1) == "string" then
@@ -23,11 +24,12 @@ local Student = {}
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Student.__index = Student
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setmetatable(Student, Person) -- extends
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function Student:read(arg1)
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if type(arg1) == "number" then
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print("I read on table n°: " .. arg1)
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function Student:read(...)
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local args = {...}
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if type(args[1]) == "number" then
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print("I read on table n°: " .. args[1])
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else
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Person.read(self, arg1)
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Person.read(self, ...)
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end
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end
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