11.5. Support for parameter checking.   

Parameter checking suffers in some languages when:
(1) Mutually recursive procedures are used in one-pass compilers. 


     Solution:   Make it two pass or

                Forward declarations with all parameters.

(2) Separate compilation of procedures is allowed and compiler doesn't have access to external declarations. 

Solution:

  (1)  Declare the procedures as external again with full

      parameter description.  CAN still cheat.

  (2)  Smart linker - NOT ALWAYS POSSIBLE.

  (3)  Leave summarised declarations lying about which must be

      used in compiling all programs using these procedures.

       MODULA 2, Java classes.

(3) Compiling a program which allows procedures as parameters which do not have a mechanism for completely describing that procedures parameters. i.e. in Pascal: 

                procedure fish(i,j:integer; procedure y);

                begin

                         :

                      y(1,2,3);

                         :

                end; 


     How does it do the correct checking at compile time?

     Type, number, order .....  No way at compile time.


Solution:

  runtime checking --> check against information left from

        descriptors.

 Some compilers require you to specify full parameter specs

  of the procedure parameter.

This is only of use in checking legality within fish.