Good morning. This is functions.

Please make sure that you have the handout in front of you. If you don’t

have it go and get it. This is what the two handouts look like. We’re going to

go through five different functions that Visual Basic provides. Those five

functions allow you to do a variety of tasks very quickly. The first one that

I’m going to show you is Str$ What Str$ does is it takes a number and it turns it into a string. You’ll

notice that I’ve also got two green boxes. The first one:

Integers, singles, doubles, longs are all automatically converted to strings when

they’re concatenated. Remember how we just learned about the ampersand? When

you use the ampersand with a numeric value it will automatically convert it

to a string. Str$ tells the program I want you

to convert this number to a string. Sometimes you need it, sometimes

you don’t. The word we use is explicit. That means you are giving a

specific instruction. Take a look at the code snippet that I’ve got here.

‘X is assigned 5″. Then I’m going to

create my message (Msg) and to Msg I assign the answer is which is a string.

Then I turn my number into a string. Display the message.

You have not yet learned how to use MsgBox but it’s a very easy way of

showing a message; a string output to the user. The second function is called Val.

Val extracts the value of a string and it returns the numeric

value. If string contains a number it will give you a numeric value. in the green box notice Val. Val strips away all spaces

and tabs. If you enter a space into a string Val ignores it. Val also stops

reading the string as soon as it it finds a character that it cannot

recognize as a number. The letter G is not part of any decimal numbering system

so G would have to be rejected. On the right

we’ve got three points the first is that Val turns a string into a number. The

second is if you give Val a string that isn’t a number what it gives you is 0.

This is a strength and a weakness. What it means is that you can’t rely on Val

telling you that the string is not a number. We actually have a specific

function that will test to see whether a string is a number but we don’t

introduce you to that yet. We’re sticking with Val. This

works. What I’m trying to tell you is you can’t be sure if your string is 0 or

if your string isn’t a number. That’s okay. Finally,

remember that E-notation is considered numeric. Val is capable

of taking E-notation and converting it into a numeric value. I have a

number of examples. They match up with your sheet. In the case of Val(645.23). That is pretty straightforward it

will convert to 645.23. The next one Val(“22 Acacia”). Val recognizes 22

and then it stops. It sees the space and then

it stops at the ‘a’ where it can’t figure out what’s going on. You end up with

22. Val(“Seven”). What do you think this is gonna be? 0.

It obviously is not anything numeric The Val(“198 43rd Street”).

I’d like you to take a moment and try to predict what is going

to come out. It ignores the spaces so it strips the leading spaces

and it ignores the space between 198 and 43 to give you 19,843. The next one.

the Val of an empty string is 0. Val(“0”) is 0 The Val of

729 East 49th Street. What do we think that’s going to be? The “E” counts as

‘to the power of 10’. It is going to be the E-notation. This actually would give you a very large number. And the

last one 729 is what you would get because W is not part of E-notation.

The third function function involves a number line and it

is Int(). it’s an interesting function. What it does is it returns the largest

integer less than or equal to the number. One thing that will catch people

off-guard is negative numbers. Pay close attention to the examples on the next

slide for the negative numbers. I’ve got my examples. I’ve got a number line here at the top and the examples on the side. First one. Int(4.2). You’ll notice the circle

that appeared on the number line. That represents 4.2. When we apply the

function Int() to it we end up with the value 4. Notice how it goes back to the

largest integer less than or equal to 4.2. 3.7. It’s appeared on the number line and notice

what’s going to happen when we apply Int() to it. We end up with 3. 3.7 goes back

to the largest integer less than or equal to it. 0.97. Very close to 1. If we were rounding it would round up to 1 but

we’re not rounding we are applying Int(). It goes down to 0. Next, -3.6. This is what catches people off guard if

they don’t think about the number line. You can follow closely what’s going to

happen. It’s going to go down to -4. It makes perfect sense when you look

at the number line. It is not toward 0, it’s towards the next

largest integer less than or equal to it. -1.2 has appeared on the number line.

It will go down to -2. We’ve got some additional examples.

18.99999. will give you 18. -99.7

becomes negative 100. Think of it always going to the left on

the number line. The fourth function is finding the square root

of a number. Quite straightforward. Sqr() of a number

returns the square root of a number. There is only one restriction: you can’t

have a negative number. We have three examples. The square root of 49 is 7. The square root of 27.04 is 5.2. The square root of -25… Error! The final

function is the absolute number function. It returns the absolute value of the

number given to it and in case you’ve forgotten what an absolute number is

it’s the magnitude of a real number without regard to its sign. What

exactly is absolute? It’s merely the numeric value without the sign. For

example Abs(9) is 9. The absolute value of -5 is 5 because we

ditched the negative sign. The absolute value of 0 is 0. Here you have the three

possible inputs. There is nothing else inside the real number system that you

can give to Abs(). That’s it. We only need three examples to cover all bases so the

last thing we’re going to do is combine functions. The first function takes the

square root of the absolute value of these squares so we’ve got a

difference of squares and our difference of squares is 64 subtract

100 is negative 36. W e’re not concerned about the negative 36 because it becomes

positive 36 through the Abs() function then we can take the square root of 36

to give us 6. Here you can see that you can combine multiple functions to

accomplish something. A second example. You will also see this on an

evaluation at some point. In fact, just so you know, you won’t be getting

calculators on your tests. You WILL get this kind of question on

your test and you cannot use a calculator. The reason for that is I

don’t need to know decimals. We take the Int() of the square root of 79. You ask

“how can we possibly do that?” First of all it’s going to be the Int() of eight

point something. I don’t exactly know what the decimal is. I don’t care what

the decimal is because the Int() takes my value and it returns the next highest

integer that is less than the value so I get eight. Now let’s take a look at the details of that

particular question. You know a few things. The first thing you know is that

the square root of 64 will be less than the square root of 79 which will be less

than the square root of 81 you also know that the square root of 64 is 8 by now I

hope you’ve learned your basic square roots you also know that the square root

of 81 is 9 so you can infer that the square root of knit 79 has to be greater

than 8 and it has to be less than 9 greater than 8 less than 9 if you apply

int to that you will get 8 yes on a test would you have to show all of this blue

writing no you would not I would basically expect you to write what you

see here in black that would be as much as I need what I would recommend if you

don’t already know them is to memorize the first five or six more advanced

square roots so I presume that everybody knows square root of 1 square root of 4

square root of 9 square root of 16 take a moment memorize these if you

haven’t now this is the end of functions at this point you will get practice

sheets for functions for the most part you shouldn’t run into problems the one

thing that I do see causing people confusion is the int function so do pay

attention to all of the questions that relate to int especially if you find

working outside of a number line confusing so to try to focus on how to

use the number line to solve int type