Procedures and Functions  109  Figure 11.f  Syntax diagram for  ActualParameterList  Figure 11.e  Syntax diagram for  F ormalParameterList  procedure declaration. The correspondence is established by  the positioning of the parameters in the lists of actual and  formal  parameters.  Parameters  provide  a  substitution  mechanism  that  allows  a process  to  be  repeated  with  a  variation of its arguments (e.g.,  MinMax  is activated twice to  scan array  A and once to scan array B). There exist four kinds  of  parameters:  value  parameters,  variable  parameters,  procedural parameters  (described in  Section  11.A.4),  and  functional parameters (described in Section l1.B.l).  I'----~  Typeldentifierr------..  ConformantArraySchema  ProcedureOrFunctionHeadingf---~'---<  r---~---.,--------+l  Variable  f------:r--~-___r  1'-----.1 Expression 1----"'1  Procedure Identifier  '----.II  '---.!  Functionldentifier  1----' 