Question

Under Unix C-shell environment, you can create variables using either set or setenv. What is the difference between these two types of variables?

Does Python have array type? Why or why not? Give some reasoning.

Create a class for watch with at least two method

Create two subclasses for mechanical watch and solar watch. Create at least two methods for each subclass.

Write regular expression to match scientific notation numbers. Your regular expression coefficient can be either integer or float.

Answer 1

1)

All variables set with setenv command are automatically exported to subshell. All csh variables set to with set command are NOT automatically exported to subshell. In this example, set an enviorment variable called vech using set command:

set vech=bus echo "$vech"

Start a new shell
csh
Try to display $vech, enter:

echo "$vech"

Sample outputs:

vech: Undefined variable.

Now, try same with setenv command:

setenv jaildir /nas/httpd echo "$jaildir" csh echo "$jaildir"

Sample outputs:

/nas/httpd

In short, set command is used for this shell and setenv for this and any subshells. Usually, all system environmental variable such as $HOME, $USER, $MAIL, $PATH, and others are defined using setenv command.

2) Python does not have array type.

Because Python is a dynamically-typed language. Arrays imply some sort of type (array of int, array of float, etc.).

Python has the list type, which is heterogeneous:

1. >>> mylist = [1, 2, 3, 'four']
2. >>> mylist
3. [1, 2, 3, 'four']

It’s somewhat like an array, but as you can see, you need not fill it with objects of the same type (although it’s typically used to hold objects of a single type).

If you want to enforce typing, there is an array type which can be imported:

1. >>> from array import array
2. >>> x = array('i')
3. >>> x.append(1)
4. >>> x
5. array('i', [1])
6. >>> x.append(2)
7. >>> x
8. array('i', [1, 2])
9. >>> x.append(3.3)
10. Traceback (most recent call last):
11. File "<stdin>", line 1, in <module>
12. TypeError: integer argument expected, got float

In addition, if you are doing statistics, Data Science, or a field where you need true numerics, you can use the numpy package, which has an array type:

3) NOTE: Since you have not mentioned the language, I am providing the code in Java.

CODE

class Watch {

private String model;

private double price;

public Watch(String model, double price) {

super();

this.model = model;

this.price = price;

}

/**

* @return the model

*/

public String getModel() {

return model;

}

/**

* @param model the model to set

*/

public void setModel(String model) {

this.model = model;

}

/**

* @return the price

*/

public double getPrice() {

return price;

}

/**

* @param price the price to set

*/

public void setPrice(double price) {

this.price = price;

}

}

NOTE: As per Chegg policy, I am allowed to answer only 3 questions (including sub-parts) on a single post. Kindly post the remaining questions separately and I will try to answer them. Sorry for the inconvenience caused.