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85 lines
2.1 KiB
Markdown
85 lines
2.1 KiB
Markdown
---
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title: "12-pointers-to-routines"
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aliases:
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tags:
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- cosc204
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- lecture
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sr-due: 2022-09-08
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sr-interval: 3
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sr-ease: 250
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---
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compiler ⇒ converts high level language description of program into assembly description of the program
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assembler ⇒ converts assebly language description into machine code description
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loader ⇒ loads program into memory, loaded at $4000
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data has an address in memory, so does the application. Therefore functions must also have an address in memory which we can access
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# pointers to routines
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```
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int (*method)(int param)
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```
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to assign a pointer to a routine
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```
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method = square;
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```
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to call the routine
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```
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result = method(6);
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```
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## basic example
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## pointer as member of a struct;
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pointers to routines can beused anyqhere variables can
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- member of struct
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- parameter to other routine
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# modules
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we can break programs into functional modules
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- each modules excapsulates one behaviour
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- give us a way of data hiding
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add pointer to structs as parameters to methods in modules
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- call this an abstract data type ADT
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- we communicatre with an ADT via its public interface
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- so that the implementation details are hidden
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method in this struct are "black box"
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we gain
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- abstraction
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- our queue has a print method, so could out stack, tree, and so on
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- we call ob->print() without needing to know (exactly) which print method is called
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## constructor
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creates object, initialises it and sets up function pointers
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## destructor
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good to use. help with closing things and freeing memory
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# modules overview
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c programs consist of .c and .h files
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- put ADT declarations in the .h (header) files
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- we can `#include` these files if we want to use the ADT in a program
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- put routine implementations in .c files
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## queue header
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pragma says include only once: prevent include loops
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