CODEWITHSUNDEEP
syntaxfunction-pointersmodula-2
c4bbage
c4bbage

Reputation: 113

Modula-2: how to assign a procedure to a pointer?

I am stuck with the assignment of a procedure to a pointer in Modula-2. 

PROCEDURE print(node : Node_ptr);
BEGIN
(* some code *)
END print;

TYPE Node_ptr   = POINTER TO Node;
TYPE Visit_ptr  = POINTER TO PROCEDURE (Node_ptr);

TYPE
    Node = RECORD
        parent  : Node_ptr;
        left    : Node_ptr;
        right   : Node_ptr;
        id      : INTEGER;
        visit   : Visit_ptr;
END;

This somehow compiles.

But I do not know how to assign the print procedure to the visit member of my Node record. I need something like this:

node^.visit^ := print;

(Even the POINTER TO PROCEDURE definition took me a while to figure out...)

Upvotes: 0

Views: 323

Answers (1)

Nemo
Nemo

Reputation: 66

Your assignment syntax is correct (after you declare node as Node_ptr and allocate space to it).

For more information, I would recommend reading Wirth, "Programming in Modula-2". You can find good used copies USD. It is terse but contains probably all you need. (Other tutorials may be found on http://freepages.modula2.org/tutor.html .)

Upvotes: 2

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