Determining When Procedures Require Explicit Interfaces

A procedure must have an explicit interface in the following cases:

• If the procedure has any of the following:
  
  
  • A dummy argument that has the ALLOCATABLE, ASYNCHRONOUS, OPTIONAL, POINTER, TARGET, VALUE, or VOLATILE attribute
    
    
  • A dummy argument that is an assumed-shape array
    
    
  • A result that is an array, or a pointer, or is allocatable (functions only)
    
    
  • A result whose length is neither assumed nor a constant (character functions only)
  
  
• If a reference to the procedure appears as follows:
  
  
  • With an argument keyword
    
    
  • As a reference by its generic name
    
    
  • As a defined assignment (subroutines only)
    
    
  • In an expression as a defined operator (functions only)
    
    
  • In a context that requires it to be pure
  
  
• If the procedure is elemental

See Also

• Optional arguments
• Array arguments
• Pointer arguments
• CALL for details on argument keywords in subroutine references
• Function references for details on argument keywords in function references
• Pure procedures
• Elemental procedures
• Defining Generic Names for Procedures for details on user-defined generic procedures
• Defining Generic Operators for details on defined operators
• Defining Generic Assignment for details on defined assignment