Time for an 2014 update…

Task/Call-a-function/Deja-Vu/call-a-function.djv

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+# all functions used are from the standard library
+# calling a function with no arguments:
+random-int
+# calling a function with a fixed number of arguments:
++ 1 2
+# calling a function with optional arguments:
+# optional arguments are not really possible as such
+# generally differently named functions are used:
+sort [ 3 2 1 ]
+sort-by @len [ "Hello" "World" "Bob" ]
+# calling a function with a variable number of arguments:
+# generally with a special terminator value, which one depends
+# on the function called
+concat( 1 2 3 )
+[ 1 2 3 ]
+set{ :foo :bar :spam }
+# calling a function with named arguments: not possible
+# using a function in first-class context within an expression
+$ @-- @len # $ is "compose", so the function returned is "one less than the length"
+# obtaining the return value of a function
+# return values are always pushed on the stack, so you don't need anything special
+random-int
+# discarding the return value of a function
+drop random-int
+# method call:
+local :do { :nuthin @pass }
+do!nuthin
+!import!fooModule # same as eva!import :fooModule
+# arguments are passed by object-identity, like in Python and Lua
+# partial application is not possible, due to the fact that
+# a function's arity is a property of its behavior and not
+# of its definition

Task/Call-a-function/Liberty-BASIC/call-a-function.liberty

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+'Call a function - Liberty BASIC
+
+'First, function result could not be discarded
+' that is, you cannot do "f(x)" as a separate statement
+
+'Calling a function that requires no arguments
+res = f()   'brackets required
+
+'Calling a function with a fixed number of arguments
+res = g(x)
+res = h(x,y)
+'Calling a function with optional arguments
+    'impossible for user-defined functions
+    'Some build-in functions ex. INSTR and MID$ could be called with last argument omitted
+'Calling a function with a variable number of arguments
+    'impossible
+'Calling a function with named arguments
+    'impossible
+'Using a function in statement context
+    'impossible (see starting notice)
+'Using a function in first-class context within an expression
+    'impossible
+'Obtaining the return value of a function
+res = g(x)
+'Distinguishing built-in functions and user-defined functions
+    'I would say impossible. Though built-in functions could be EVAL'ed,
+    'while user-defined would not be called (tries address array instead).
+    'Still cannot distinguish user-defined function from array.
+'Distinguishing subroutines and functions
+    'then defined, subroutines and functions defined with words
+    'SUB and FUNCTION (case incensitive)
+    'Then used, function used as expression (with return value),
+    res = g(x)
+    'while subroutines called with special keyword CALL and without brackets
+    call test x, y
+'Stating whether arguments are passed by value or by reference
+    'Variables passed as arguments into functions and subs are passed "by value" by default
+    'parameters could be passed "by reference" if formal parameter in sub/function definition uses the "byref" specifier
+    'Then calling a function, you can prevent pass by reference by changing variable to expression
+    '   like x+0, x$+"" or just (x), (x$)
+'Is partial application possible and how
+    'impossible