Local Routines or Nested Routines

How to declare Local routines in delphi ?

It is possible to declare local procedures or

Functions within a procedure or function.

Though it seems some how unusual at the first glance to declare

Local routines within a routine, it is efficient to do this.

If we do not need them anywhere other than the routine, why should

make them public even within the unit ? Let us place them in their proper

place, proper routines in proper place !



We declare local variables, constants and types before the BEGIN statement of

a function or procedure. We can also include local routines here. Though it is

efficient to include local routines here, but, in practice, very few delphi programmers

use these techniques.



Example:



Procedure PublicProc(p1:TypeofP1;p2:TypeofP2;....pn:TypeOfPn);

var

  v1:TypeofV1;

  V2:TypeofV2;

  .....

  Vn:TypeofVn;

const

  c1:TypeofC1;

  ............

  ............



  procedure LocalProcedure1(p1:TypeofP1;p2:TypeofP2;....pn:TypeOfPn);

  var

    .........

    .........

  begin

    .........

    .........

  end;

  procedure LocalProcedure2(p1:TypeofP1;p2:TypeofP2;....pn:TypeOfPn);

  var

    .........

    .........

  begin

    .........


    .........

  end;

  Function LocalFunction1(p1:TypeofP1;p2:TypeofP2;....pn:TypeOfPn):ResultType;

  var

    .........

    .........

  begin

    .........

    .........

    result:=.....

  end;

  Function LocalFunction2(p1:TypeofP1;p2:TypeofP2;....pn:TypeOfPn):ResultType;

  var

    .........

    .........

  begin

    .........

    .........

    result:=.....

  end;



begin {PublicProc}

  ...........

  '''''''''''

  LocalProcedure1(...., ...., ....);

  ...........

  LocalProcedure2(...., ...., ....);

  ...........

  v1:=LocalFunction1(...., ...., ....);

  ...........

  v2:=LocalFunction2(...., ...., ....);

  ...........

  '''''''''''

end;{PublicProc}



In this example, the scope of the nested routines

LocalProcedure1,

LocalProcedure2,

LocalFunction1 and

LocalFunction2

is limited only to PublicProc. No other routines in the same unit or in other

units can see them.



For some real example of nested routines, please have a look in the article

"Converting Numbers to words !".


 

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