Initial data commit

Task/Call-a-function/Lua/call-a-function.lua

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+-- Lua functions accept any number of arguments; missing arguments are nil-padded, extras are dropped.
+function fixed (a, b, c) print(a, b, c) end
+fixed() --> nil nil nil
+fixed(1, 2, 3, 4, 5) --> 1 2 3
+
+-- True vararg functions include a trailing ... parameter, which captures all additional arguments as a group of values.
+function vararg (...) print(...) end
+vararg(1, 2, 3, 4, 5) -- 1 2 3 4 5
+
+-- Lua also allows dropping the parentheses if table or string literals are used as the sole argument
+print "some string"
+print { foo = "bar" } -- also serves as a form of named arguments
+
+-- First-class functions in expression context
+print(("this is backwards uppercase"):gsub("%w+", function (s) return s:upper():reverse() end))
+
+-- Functions can return multiple values (including none), which can be counted via select()
+local iter, obj, start = ipairs { 1, 2, 3 }
+print(select("#", (function () end)())) --> 0
+print(select("#", unpack { 1, 2, 3, 4 })) --> 4
+
+-- Partial application
+function prefix (pre)
+    return function (suf) return pre .. suf end
+end
+
+local prefixed = prefix "foo"
+print(prefixed "bar", prefixed "baz", prefixed "quux")
+
+-- nil, booleans, and numbers are always passed by value. Everything else is always passed by reference.
+-- There is no separate notion of subroutines
+-- Built-in functions are not easily distinguishable from user-defined functions