2.7 Enum & Operator Overloading

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Del curso dictado por University of California, Santa Cruz

C++ For C Programmers, Part A

559 calificaciones

University of California, Santa Cruz

C++ For C Programmers, Part A

559 calificaciones

This course is for experienced C programmers who want to program in C++. The examples and exercises require a basic understanding of algorithms and object-oriented software.

De la lección

Module 2

Review of Dijkstra's shortest path algorithm. C++ Functions and Generics. C++ classes and OO. Point as an example.

2.1 C++ Generics and Functions14:13

2.2 Multiple Template Arguments8:48

2.3 Graph Theory & Algorithms9:33

2.4 Graph as a Data Structure11:10

2.5 Dijkstra Shortest Path16:42

2.6 C++ Creating Types5:22

2.7 Enum & Operator Overloading4:04

2.8 Example: typedef days18:39

2.9 Natural Way to Build Widgets6:47

2.10 C++ Point26:58

Conoce a los instructores

Ira Pohl
Professor
Computer Science

Object oriented programming lets us program naturally in new domains,

domains that not necessarily have types in the native language that fit the domains.

So for example,

we might want to write programs that involve manipulation of colors.

Imagine having a windowing system and

inside your windowing system you have different menu options.

And possibly within the window options,

you're using color to add different levels of expressivity.

So you might want a color type.

This is a simple form of type extensibility,

typically colors could be defined as a small, discrete set of items.

So here we see,

an enumerated type which is one form of type extensibility in the C++ language.

That has a color RED, a color WHITE, and a color GREEN.

Now, with these colors, this is basically a form of simple integer type,

and the reason we use capital RED is that's just,

that's an identifier, that's an enumerator.

So enum id.

And capitalization.

Are a convention.

They just highlight that, we're expressing a form of integer constant.

And red, when no value is specified, will be automatically assigned zero.

That's in the old grand tradition of the C community.

Everything starts at zero.

WHITE will be 1, and GREEN will be 2.

And that's what we'll do normally.

We also will have the ability to override these values by being explicit.

We could say, white is 3.

And that would mean, that red starts zero, white starts at three, and

then the sequence continues from three to four.

Now, why should we use enum?

Some of you have experienced enum.

Enum was added even to the C language,

and in many other programming languages, there are enumerated types.

It's a multiple choice question, just take a second, Can you use a named

integer instead of an enumerated type to get that kind of constant?

Can you use a #define much like in the pre processor keeping C

old style, for these enumerator constants like red and white.

Or is it best to have a small related set of constants?

So which reason exists for using enum?

It is quite true that, you can just use cost

declaration for example, if you wanted true and

false as two related constants, we can say,

constant TRUE is 1 and constant,

FALSE is 0 then we would have that.

We can also use this in old C style, but again, there's safety issues.

But enumerated types are even better than either of these others,

where there is a grouping of related constants.

Where you wanna think about as type extensibility and

not just arbitrary name integer constants.

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