body

#body

##Syntax A bodyDeclaration is one of:

(a) body procedure procedureId statementsAndDeclarations end procedureId (b) body function functionId statementsAndDeclarations end functionId (c) body procedure id [(paramDeclaration {, paramDeclaration })] statementsAndDeclarations end id (d) body function id [ ( [paramDeclaration {, paramDeclaration } ]) ] : typeSpec statementsAndDeclarations end id

##Description A body declaration is used to resolve either a forward subprogram or a deferred subprogram.

You declare a procedure or function forward when you want to define its header but not its body. This is the case when one procedure or function calls another, which in turn calls the first. This situation is called mutual recursion. The use of forward is necessary in this case because every item must be declared before it can be used. The forward declaration must be followed by a body declaration for the same procedure or function. For details, see forward declarations.

When a procedure or function in a class is declared to be deferred (or simply exported from the class), it can be resolved or overridden afterward by giving its body further down in that class or in descendant classes. The overriding procedure must use the keyword body. See class or "implement by" for examples.

##Details You can specify the parameter and return values of the subprogram in the body declaration. However, the names and types of the parameters and return values must match the initial declaration exactly, or a warning results and the parameter list and return values from the body declaration are ignored.

##Example The example given here is part of a complete Turing program that includes an explanation of forward declarations.

    var token : string
    forward procedure expn (var eValue : real)
        import forward term, var token
    � other declarations appear here �
    body procedure expn
        var nextValue : real
        term (eValue)               % Evaluate t
        loop                        % Evaluate { + t}
            exit when token not= "+"
            get token
            term (nextValue)
            eValue := eValue + nextValue
        end loop
    end expn

##Details The syntax of a bodyDeclaration presented above has been simplified by omitting the optional result identifier, import list, pre and post condition and init clause. See procedure and function declarations for descriptions of these omissions.

The "function" or "procedure" token in the declaration is now optional. In other words the following code fragment is legal

    forward procedure p
    �
    body  p
    �
    end p

##See also class.html, forward.html and [implement_by.html](implement by)