Delphi Language Guide Delphi for Microsoft Win32 Delphi for the Microsoft. Net framework

Function Declarations
A function declaration is like a procedure declaration except that it specifies a return type and a return value. Function
declarations have the form
function functionName(parameterList): returnType; directives;
  localDeclarations;
begin
  statements
end;
where functionName is any valid identifier, returnType is a type identifier, statements is a sequence of statements
that execute when the function is called, and (parameterList), directives;, and localDeclarations; are optional.
The function's statement block is governed by the same rules that apply to procedures. Within the statement block,
you can use variables and other identifiers declared in the localDeclarations part of the function, parameter names
from the parameter list, and any identifiers within whose scope the function declaration falls. In addition, the function
name itself acts as a special variable that holds the function's return value, as does the predefined variable 
Result
.
As long as extended syntax is enabled (
{$X+}
), Result is implicitly declared in every function. Do not try to redeclare
it.
For example,
function WF: Integer;
begin
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---

  WF := 17;
end;
defines a constant function called 
WF
 that takes no parameters and always returns the integer value 17. This
declaration is equivalent to
function WF: Integer;
begin
  Result := 17;
end;
Here is a more complicated function declaration:
function Max(A: array of Real; N: Integer): Real;
var
X: Real;
I: Integer;
begin
  X := A[0];
  for I := 1 to N - 1 do
    if X < A[I] then X := A[I];
  Max := X;
end;
You can assign a value to 
Result
 or to the function name repeatedly within a statement block, as long as you assign
only values that match the declared return type. When execution of the function terminates, whatever value was last
assigned to 
Result
 or to the function name becomes the function's return value. For example,
function Power(X: Real; Y: Integer): Real;
var
  I: Integer;
begin
  Result := 1.0;
  I := Y;
  while I > 0 do
   begin
    if Odd(I) then Result := Result * X;
    I := I div 2;
    X := Sqr(X);
   end;
end;
Result
 and the function name always represent the same value. Hence
function MyFunction: Integer;
begin
  MyFunction := 5;
  Result := Result * 2;
  MyFunction := Result + 1;
end;
returns the value 11. But 
Result
 is not completely interchangeable with the function name. When the function name
appears on the left side of an assignment statement, the compiler assumes that it is being used (like 
Result
) to
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---

track the return value; when the function name appears anywhere else in the statement block, the compiler interprets
it as a recursive call to the function itself. 
Result
, on the other hand, can be used as a variable in operations,
typecasts, set constructors, indexes, and calls to other routines.
If the function exits without assigning a value to 
Result
 or the function name, then the function's return value is
undefined.