Passing multiple results back from a function

Have you ever wondered why you can pass in as many parameters as you like to a function, but only return one? It seems rather unfair, doesn't it - especially as you may have lots of results.

In fact, in some languages such as Lua you can pass multiple values back:
  a,b,c = symie(4,7,9)
(see source code)

and in others such as Python and Perl you can return one collection which contains multiple items. Here's an example return in Python:
  return (net, tax)
and the code that collects the two return values from the function:
  shop, taxman = both(amount)
(see source code of function and caller).

Even less directly, you can return hashes, lists or objects in other languages, and in C you can return a pointer to a structure. Perl often sets special global variables (to take what I sometimes describe as 'side effect' results) which are all well and good if you know what is happening, and most languages allow some sort of global variable which is OK if used in extreme moderation!
(written 2009-08-13)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles

U106 - Lua - Functions.
  [1685] Short circuit evaluation (lazy operator) in Lua - (2008-06-22)
  [1697] Sorting in lua - specifying your own sort routine - (2008-07-05)
  [1699] If you are learning Lua, here are some more examples - (2008-07-06)
  [1743] First class functions in Lua lead to powerful OO facilities - (2008-08-07)
  [1744] Lua examples, Lua Courses - (2008-08-08)
  [1847] Lua - IAQ (Infrequently Answered Questions) - (2008-10-18)
  [2312] What are closures in Lua? - (2009-07-31)
  [2347] Dot, dot, dot in Lua - variable length parameter lists - (2009-08-11)
  [2455] Lua examples - coroutines, error handling, objects, etc - (2009-10-15)
  [2723] Returning multiple values from a function - Lua - (2010-04-15)
  [2949] Lua - variable function arguments and select - (2010-09-08)
  [3695] Functions are first class variables in Lua and Python - (2012-04-13)

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