Chandrika: Created page with '{| border=1 !Time !Narration |- |0:0 |Welcome to the Spoken Tutorial on Advanced Function. Here, I'll show you how to create a little calculator program. |- |0:04 |We will deal w…'

2012-11-29T06:38:46Z

Created page with '{| border=1 !Time !Narration |- |0:0 |Welcome to the Spoken Tutorial on Advanced Function. Here, I'll show you how to create a little calculator program. |- |0:04 |We will deal w…'

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{| border=1
!Time
!Narration
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|0:0
|Welcome to the Spoken Tutorial on Advanced Function. Here, I'll show you how to create a little calculator program.
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|0:04
|We will deal with a function that allows you to input a value. Then gain a value out this, after a mathematical operation
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|0:13
|So, we'll create a function in the same way that we've done before. I'll call this 'calc'
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|0:19
|And I'm going to create my block first. Here inside, I'll type 'number1', 'number2' and an 'operator'
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|0:28
|Now this will be a numerical value. This will be an integer or decimal, depending on the user-input. This will also be the same and this will be the string value of either 'add' 'subtract' 'multiply' or 'divide'
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|0:44
|Now inside our function we need to start creating our code. I'm going to create a switch statement inside.
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|0:54
|I'll say switch and put the switch condition or rather the input of the switch is 'op'
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|1:03
|I'll create a block for this and I'll say case = plus then carry out this.
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|1:14
|I'll make a new variable called 'total' which will be equal to 'num1' which is input here plus 'num2'
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|1:28
|I'll break that with a semicolon. Now there's probably a much easier way to do this by combining the switch statement with a function.
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|1:39
|So you will be able to use all different kinds of things inside other statements and inside functions.
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|1:45
|So I have created a case for 'plus'. So when this equals to 'plus' supplied by the user, we have 'num1' added to 'num2'.
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|1:57
|Now we need to go down and create another 'case', which is 'minus'. I'll type total = 'num1' - 'num2'
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|2:10
| We will scroll down. Make sure you break that.
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|2:16
|We'll now copy this code down.
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|2:20
|Here we'll say 'multiply' and here we'll say 'divide' and make sure you change the sign here.
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|2:27
|Now if you don't understand what is going on here please feel free to contact us via e-mail. I hope every probable confusion will be resolved in that way.
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|2:36
|In the default we're going to echo out 'unknown operator'. OK?
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|2:45
|Let me just run through this. Then we will start to call the function.
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|2:50
|I have got a function called calculator or calc for short, which takes a number as input, then a second number and then an operator which can either be 'plus' 'minus' 'multiply' or 'divide'.
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|2:58
| As you have probably seen in my mathematical operator - sorry in my arithmetic operator tutorial.
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|3:14
|Now we have a switch statement inside, which takes this 'op' into account. It takes what has been entered. Now if it equals to a 'plus', remember that it switches over to this statement. It is easier to write and is much more efficient.
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|3:32
|If it equals to a 'plus' then we will create a new variable called 'total'.
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|3:39
|That's going to be equal to the first number which was entered and added to the second number which was entered.
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|3:45
|Here we will say if it's a 'minus', then the variable 'total' - okay remember, the variable 'total' will only be set once for each case either plus or minus - so this total variable going to be number 1 - number 2 and the same for multiply and divide as well.
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|4:10
|Now this would do absolutely nothing. Refresh this. Now, if we enter this page, there is nothing, because we haven't called our function.
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|4:20
|Now to call our function, as you know, we will just say calc and we will put our values in.
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|4:25
|Let's us just give it two numbers say 10 and 10 and a 'plus' . Okay, so that will be 20. Now watch what happens when I refresh this. Nothing. Now why?
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|4:45
|The reason is that we haven't echoed this out. We've just set it as a variable.
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|4:50
|So what we would ideally do is we will echo what has been out put from calc. Now, at that moment this won't do anything if we do a refresh
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|5:00
|We have got nothing, because, there is no return output. So, in each case what we should say is 'return total'.
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|5:16
|What this does is - If you think of the function as a variable it sets the function's value as the total.
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|5:26
|As long as you say return whatever you say here the function will equal that.
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|5:31
|So we are going to say return total and we are going to copy that and paste it down for each case.
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|5:42
|Okay so obviously we don't need to do that for unknown operator. This is because, there is no operator to be found here.
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|5:49
|And we can refresh that.
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|5:49
|We still don't have anything. Guess why?
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|5:55
|The reason this is not working is because I've echoed this inside a function. That's a mistake.
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|6:03
|You can see the bracket of a function that starts here and ends here
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|6:08
|I'll place this underneath here, where it should be and then refresh it. It is 20 okay, so we can see the 10 + 10 is 20 through our function
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|6:24
|So let's pick some different values, say, 13 and 7 and divide. Let's see what we get.
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|6:35
|Okay, we have got a quiet long decimal number. So you can see that this is quite a good function that we have made. We have got our first number, our second number and an operator.
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|6:46
|And through a switch statement it detects which one and performs the relevant operation to it.
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|6:54
|An unknown operator error will be given if it can't be determined.
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|6:58
|So, for example let's take 'a' which is not a valid operator. As soon as we refresh it's going to unknown operator. This brings us to the end of the tutorial on advanced functions. We saw that we can input a value and then returned a value echoing out using a return command.
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|7:13
|This is Sidharth dubbing for the Spoken Tutorial Project. Thanks for watching.
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PHP-and-MySQL/C2/Functions-(Advanced)/English - Revision history

Chandrika: Created page with '{| border=1 !Time !Narration |- |0:0 |Welcome to the Spoken Tutorial on Advanced Function. Here, I'll show you how to create a little calculator program. |- |0:04 |We will deal w…'