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+[Verano 2016- Tatiana]
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A good way to organize and structure computer programs is dividing them into smaller parts using functions. Each function carries out a specific task of the problem that we are solving.
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-You've seen that all programs written in C++ must contain the `main` function where the program begins. You've probably already used functions such as `pow`, `sin`, `cos`, or `sqrt` from the `cmath` library. Since in almost all of the upcoming lab activities you will continue using pre-defined functions, you need to understand how to work with them. In future exercises you will learn how to design and validate functions. In this laboratory experience you will search and display information contained in a DVD data base to practice declaring simple functions and calling pre-defined functions.
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+You've seen that all programs written in C++ must contain the `main` function where the program begins. You've probably already used functions such as `pow`, `sin`, `cos`, or `sqrt` from the `cmath` library. Since in almost all of the upcoming lab experiences you will continue using pre-defined functions, you need to understand how to work with them. In future exercises, you will learn how to design and validate functions. In this laboratory experience, you will search and display information contained in a DVD data base to practice declaring simple functions and calling pre-defined functions.
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##Objectives:
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2. Studied the concepts and instructions for the laboratory session.
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-3. Taken the Pre-Lab quiz that can be found in Moodle.
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+3. Taken the Pre-Lab quiz, available in Moodle.
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---
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In mathematics, a function $$f$$ is a rule that is used to assign to each element $$x$$ from a set called *domain*, one (and only one) element $$y$$ from a set called *range*. This rule is commonly represented with an equation, $$y=f(x)$$. The variable $$x$$ is the parameter of the function and the variable $$y$$ will contain the result of the function. A function can have more than one parameter, but only one result. For example, a function can have the form $$y=f(x_1,x_2)$$ where there are two parameters, and for each pair $$(a,b)$$ that is used as an argument in the function, the function has only one value of $$y=f(a,b)$$. The domain of the function tells us the type of value that the parameter should have and the range tells us the value that the returned result will have.
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-Functions in programming languages are similar. A function has a series of instructions that take the assigned values as parameters and performs a certain task. In C++ and other programming languages, functions return only one result, as it happens in mathematics. The only difference is that a *programming* function could possibly not return any value (in this case the function is declared as `void`). If the function will return a value, we use the instruction `return`. As in math, you need to specify the types of values that the function's parameters and result will have; this is done when declaring the function.
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+Functions in programming languages are similar. A function has a series of instructions that take the assigned values as parameters and performs a certain task. In C++ and other programming languages, functions return only one result, as it happens in mathematics. The only difference is that a *programming* function could possibly not return any value (in this case the function is declared as `void`). If the function returns a value, we use the instruction `return`. As in math, you need to specify the types of values that the function's parameters and result will have; this is done when declaring the function.
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###Function header:
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###Calling
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-If we want to store the value of the `example` function's result in a variable `result` (that would be of type integer), we call the function by passing arguments as follows:
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+If we want to store the value of the result of the function called `example` in a variable `result` (that would be of type integer), we call the function by passing arguments as follows:
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`result=example(2, 3.5, unCar);`
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-Note that as the function is called, you don't include the type of the variables in the arguments. As in the definition for the function `example`, the third parameter `&var3` is a reference variable; what is being sent to the third argument when calling the function is a *reference* to the variable `unCar`. Any changes that are made on the variable `var3` will change the contents of the variable `unCar`.
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+Note that as the function is called, you don't include the type of the variables in the arguments as in the definition for the function `example`. The third parameter `&var3` is a reference variable; what is being sent to the third argument when calling the function is a *reference* to the variable `unCar`. Any changes that are made on the variable `var3` will change the contents of the variable `unCar`.
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You can also use the function's result without having to store it in a variable. For example you could print it:
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int example(int, char) ;
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```
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-All of the above functions have the same name, `example`, but different parameters. The first and second functions have the same amount of parameters, but their arguments are of different types. The fourth and fifth functions have arguments of type `char` and `int`, but in each case are in different order.
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+All of the above functions have the same name, `example`, but different parameters. The first and second functions have the same amount of parameters, but their arguments are of different types. The fourth and fifth functions have arguments of type `char` and `int`, but they have a different order in each case.
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-In that last example, the function `example` is overloaded since there are 5 functions with different signatures but with the same name.
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+In that last example, the function `example` is overloaded since there are five functions with different signatures but with the same name.
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-### Default values
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+### Default values
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-Values by default can be assigned to the parameters of the functions starting from the first parameter to the right. It is not necessary to initialize all of the parameters, but the ones that are initialized should be consecutive: parameters in between two parameters cannot be left uninitialized. This allows calling the function without having to send values in the positions that correspond to the initialized parameters.
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+Values by default can be assigned to the parameters of the functions starting from the rightmost parameter. It is not necessary to initialize all of the parameters, but the ones that are initialized should be consecutive: parameters in between two parameters cannot be left uninitialized. This allows calling the function without having to send values in the positions that correspond to the initialized parameters.
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**Examples of function headers and valid function calls:**
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b. `example(5, 3.3)` In this function call only the first two parameters are given values, and the value for the last parameter is the value by default. That is, the value for `var1` within the function will be 5, that of `var2` will be 3.3, and `var3` will be 10.
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- c. `example(5)` In this function call only the first parameter is given a value, and the last two parameters will be assigned values by default. That is, `var1` will be 5, `var2` will be 5.0, and `var3` will be 10.
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+ c. `example(5)` In this function call only the first parameter is given a value, and the last two parameters will be assigned values by default. That is, `var1` will be 5, `var2` will be 5.0, and `var3` will be 10.
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**Example of a valid function header with invalid function calls:**
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a. `example(5, , 10)` This function call is **invalid** because it leaves an empty space in the middle argument.
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- b. `example()` This function call is **invalid** because `var1` was not assigned a default value. A valid call to the function `example` needs at least one argument (the first).
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+ b. `example()` This function call is **invalid** because `var1` was not assigned as a default value. A valid call to the function `example` needs at least one argument (the first).
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**Examples of invalid function headers:**
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-1. `int example(int var1=1, float var2, int var3)` This header is invalid because the default values can only be assigned starting from the rightmost parameter.
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+1. `int example(int var1=1, float var2, int var3)` This header is invalid because the default values can only be assigned starting from the rightmost parameter.
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2. `int example(int var1=1, float var2, int var3=10)` This header is invalid because you can't place parameters without values between other parameters with default values. In this case, `var2` doesn't have a default value but `var1` and `var3` do.
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##DVD movies and the DVD data base
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-DVD stands for "digital versatile disk" or "digital video disk", which is an optical disc format for storing digital information invented by Philips, Sony, Toshiba, and Panasonic in 1995. The DVD offers larger storage capacity than compact disks (CD), but have the same dimensions. DVDs can be used to store any kind of digital data, but are famous for their use in the distribution of movies.
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+DVD stands for "digital versatile disk" or "digital video disk", which is an optical disc format for storing digital information invented by Philips, Sony, Toshiba, and Panasonic in 1995. The DVD offers larger storage capacity than compact disks (CD), but has the same dimensions. DVDs can be used to store any kind of digital data, but they are famous for their use in the distribution of movies.
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-!INCLUDE "../../eip-diagnostic/DVD/en/diag-dvd-01.html"
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+!INCLUDE "../../eip-diagnostic/DVD/en/diag-dvd-01.html"
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-!INCLUDE "../../eip-diagnostic/DVD/en/diag-dvd-03.html"
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+!INCLUDE "../../eip-diagnostic/DVD/en/diag-dvd-03.html"
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-!INCLUDE "../../eip-diagnostic/DVD/en/diag-dvd-11.html"
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-!INCLUDE "../../eip-diagnostic/DVD/en/diag-dvd-12.html"
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+!INCLUDE "../../eip-diagnostic/DVD/en/diag-dvd-12.html"
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## Laboratory session
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-In this laboratory session we will be using a data base of DVD movies maintained by http://www.hometheaterinfo.com/dvdlist.htm. This database contains 44MB of information for movies that have been distributed in DVD. Some of the stored information in the database for each DVD is: DVD title, publishing studio, date of publication, type of sound, versions, price, rating, year and genre. The fields of information for each movie are stored in text with the following format:
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+In this laboratory session we will be using a data base of DVD movies maintained by http://www.hometheaterinfo.com/dvdlist.htm. This database contains 44MB of information for movies that have been distributed in DVD. Some of the stored information in the database for each DVD is: DVD title, publishing studio, date of publication, type of sound, versions, price, rating, year and genre. The fields of the information for each movie are stored in text with the following format:
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`DVD_Title|Studio|Released|Status|Sound|Versions|Price|Rating|Year|Genre|Aspect|UPC|DVD_ReleaseDate|ID|Timestamp`
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###Exercise 1
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-The first step in this lab experience is to familiarize yourself with the functions that are already defined in the code. Your tasks require that you imitate what the functions do, so it is important that you understand how to call, declare and define the functions.
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+The first step in this lab experience is to familiarize yourself with the functions that are already defined in the code. Your tasks require that you imitate what the functions do, for this reason it is important that you understand how to call, declare and define the functions.
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**Instructions**
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-1. Open the project `DVDInfo` in Qt by double clicking the file `DVDInfo.pro` in the folder `Documents/eip/Functions-DVDInfo` on your computer. You may also access `http://bitbucket.org/eip-uprrp/functions-dvdinfo` to download the folder `Functions-DVDInfo` to your computer.
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+1. Load the project `DVDInfo` into `QtCreateor`. There are two wayss to do this:
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+ * Using the virtual machine: Double click the file `DVDInfo.pro` located in the folder `home/eip/labs/functions-dvdinfo` of your virtual machine.
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+ * Downloading the project's folder from `Bitbucket`: Use a terminal and write the command `git clone http://bitbucket.org/eip-uprrp/functions-dvdinfo` to download the folder `functions-dvdinfo` from `Bitbucket`. Double click the file `DVDInfo.pro` located in the folder that you downloaded to your computer.
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2. Configure the project. The file `main.cpp` has the function calls that you will use in the next exercises. The declarations and definitions of the functions that will be called can be found in the files `movie.h` and `movie.cpp`.
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getMovieByName
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```
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-4. You can find the function definitions in the file `movie.cpp`. Note that some versions of the function `showMovie` use the object called`fields` of the `QStringList` class. The purpose of this object is to provide easy access to information fields of each movie, using an index between 0 and 14. For example, you may use fields[0] to access a movie’s title, fields[1] to access a movie’s studio, fields[8] to access its year, and so forth.
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+4. You can find the function definitions in the file `movie.cpp`. Note that some versions of the function `showMovie` use the object called `fields` of the `QStringList` class. The purpose of this object is to provide easy access to information fields of each movie, using an index between 0 and 14. For example, you may use fields[0] to access a movie’s title, fields[1] to access a movie’s studio, fields[8] to access its year, and so forth.
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-!INCLUDE "../../eip-diagnostic/DVD/en/diag-dvd-06.html"
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+!INCLUDE "../../eip-diagnostic/DVD/en/diag-dvd-06.html"
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4. For the movie in part 3 of this exercise, add the necessary code to the `main` function so that the program displays the name and the rating of the movie.
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-5. Modify the `getMovieInfo` function in the file `movie.cpp` so that it receives an additional parameter by reference to which the name of the movie will be assigned. Remember that you must also modify the function's prototype in `movie.h`.
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+5. Modify the `getMovieInfo` function in the file `movie.cpp` so that it receives an additional parameter by reference where the name of the movie will be assigned. Remember that you must also modify the function's prototype in `movie.h`.
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6. For the movie in part 3, add the necessary code to the `main` function so that, using `getMovieInfo`, it displays the name, rating, year and the genre of the movie in one line. Hint: note that the function `getMovieInfo` has parameters that are passed by reference.
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[3] http://www.soft32.com/blog/platforms/windows/keep-your-dvd-collection-up-to-date-with-emdb-erics-movie-database/
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[4] http://www.hometheaterinfo.com/dvdlist.htm
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