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♫ ♫ Opening Music
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Hello! Welcome to another lesson of their course algorithm,
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my name is Gustavo Guanabara, I am your teacher,
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and now we're going to continue the study of operators seeing the two operators missing:
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relational operators and logical operators.
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Let's go to class for us to understand the difference between them and what each will do.
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So, the last lesson we saw the entry of commands and arithmetic operators.
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Now, we'll start seeing the Relational Operators.
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And as the name suggests,
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relational operators will create a relationship between variables or expressions.
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Then you will be able to compare the variables and expressions and generate logical results,
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as true or false.
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Then the relational operators will generate as a result, always, a logical value.
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Logical operators that exist in all programming languages, including,
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ambiento in the visualg are:
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So, it is noteworthy that there is no way to do the greater than or equal, with the same symbol under the larger,
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as we do in mathematics, by keyboard typing issues.
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So we will put the biggest sign followed the same space without any sign between them.
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The same will occur pro or less,
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and we have the last two relational operators are: equal to and different from
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And worth noting that there as well as or greater and less than or equal,
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It is difficult to type "different"
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which is an equal sign "cut" in the middle.
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So pro difference operator, I'll use a smaller signal and a higher signal,
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typed with no space between them.
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and then, we will go, then by a party that practice is to compare numeric values using the VisuAlg
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and once again, as always, I will recommend.
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Open visuAlg and Assita this class with the application open
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no use getting you watch me do something
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And you find that you learned
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then the best way to learn is to practice
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because when we practice, we make mistakes and when we make mistakes, we try to fix
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and it is trying to fix what you learn, you never forget it
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then I created an algorithm and I will create three variables here
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variable A variable B variable and C, all three integer
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declaration of variables we have seen in previous lessons
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what I will do here is to make a simple assignment
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"A" gets 2 "B" receives 3 and "C" receives 5
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and now we will make some logical comparisons
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I post here. type "A" greater than "B"
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Then he will show me the result of If "A" is greater than "B"
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Running the program we have "false"
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this means . I sent write the logical result of "A" is greater than "B"
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and here, I can see the values of the variables "A" is worth 2 and "B" is worth 3
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"A" is not greater than "B", "A" is actually smaller than "B"
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as a result of the "A" greater than "B". I have the logical value "false"
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Get the idea?
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We will here little we see the logical operators.
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But the relational operators will always lead me a logical value
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That is, will always return me either true or false
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Let's see some more example
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So I'll put here for example "A" Like "B"
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"A" is 2 and "B" is 3 then "A" is not equal to "B".
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So I will return "false" value.
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This is "A" is not equal to "B"
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Similarly I can test if "A" is different from "B"
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"A" is 2 and "B" being 3 course "A" is different from "B"
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Running it returns me the value "TRUE"
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This is the answer to: "A" is different from "B"? Yes "A is different from" B "
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And as I said earlier
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relational operators will test the relationship enters variables, values or expressions
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So I can make some comparisons using values
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For example here.
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"A" is greater than 2? He will return me "FALSE"
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Because "A" is not greater than 2, if you check here.
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"A" is equal to 2
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But if I do the logical test: "A" is greater than or equal to 2?
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Running, he has returned me "TRUE"
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Because "A" is not greater than 2, but it is the same
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Then one of the two operators is going to have to lead to true
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Thus, in this manner. "A" greater than or equal to 2 results in the logical value "TRUE"
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We do now, some logical expressions tests
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Nothing prevents you do it here
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I'll test if "C" is equal to "A" + "B" (A plus B)
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We've seen the last class the arithmetic operators, and we know that this operator will perform addition
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Then it will test if "C" is equal to "A" + "B"
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"C" is 3, "A is 2, and" B "is 3.
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2 plus 3 equals 5, it will lead me to the value "TRUE"
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Let's run and see what the end result, it really was true
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Let's do another example here, let's see if "C" is greater than or equal to "B ^ A" (B raised to A)
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That is, it will make a test seeing if "C" is greater or equal than the result of "B ^ A" (B raised to A)
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"B" is 3, the high 'A'.
"3" squared, 9.
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"C" is equal to 5.
"C" is not greater than or equal to 9.
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So. We will run and it will return me "False."
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Because "B" high "A"
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Of Nine (9)
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"C" is not greater than or equal to "B" high "A"
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But if I put here
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If "C" is " 00:11:04,000
and in the latter case, if neither of the two are happy, for sure I will not be happy!
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You get the idea?
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With the operator "and" I want one thing and another.
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No use come with only one for me, because I want both.
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We will follow this same line of reasoning to the "OR" operator.
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And there is even easier for you to understand, is not it?
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Come on. We will follow the same line of reasoning.
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"Paula" and "Keziah," and now I want Paula to be happy OR Keziah be happy.
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If the two are happy, of course I'm happy.
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If only Paula is happy and Keziah not, I end up being satisfied,
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because I want Paula OR Keziah be happy.
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Any one or the other.
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Similarly, if Paula is not happy and is Keziah,
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yet still happy.
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The only case that is different in the case of the OR,
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It is when Paula is not happy and Keziah also is not happy,
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In this case, as I want Paula OR Keziah be happy, and neither is,
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I do not get happy.
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Now given to understand the difference between the operators AND and OR right?
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In the case of And I'm only happy when Paula and Keziah stay happy.
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Otherwise I'm not satisfied.
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In the case of the OR, I'm happy in either case, except in the case where the two are unhappy.
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The NOT operator is simply a logical reversal
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If Paula is HAPPY
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The NOT HAPPY SAD is
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Thinking in the same way
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If it is SAD, the SAD is NOT happy
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So, for you generate the truth table
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What are these tables we're doing
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E and OR, is easy
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All happyfaces
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You will turn into true
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All the sad faces, you will turn into false
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So it's easy, is not it?
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So whenever you have difficulty understanding the truth table
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E and OR
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Just draw smiley faces
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And then replace
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All HAPPY by V
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And all the SAD by F
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And so
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You can have the two tables TRUTHS
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The logical operators: AND and OR
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Let's do some logical tests
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Using that our same example
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We were creating in Visualg
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So we do here
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This "Type"
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I have to give two logical tests
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So if I put here
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"(True and false)"
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He will return me
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The value FALSE
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Why a REAL thing and one thing FALSE
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Give in FALSE
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But I can also use
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logical results generated by relational operators and test
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We will test for example, if A is equal to B (A = B)
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or C is greater than a (C> A)
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Let's see the result.
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In this case A is equal to B? 2 equals 3?
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No! So this one will return me false.
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C is greater than A? 5 is greater than 2?
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This one would return me true
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True or false, comes in that case.
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Paola is not happy, but quesia is happy
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as I have a "OR" my logical result will be:
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a happy or true face!
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So here we have the logical result of all ((A = B) or (C> A)) is true!
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If by chance we put a parenthesis here, and we put a non front: (not ((A = B) or (C> A)))
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it will reverse the logical result
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So; if this here: (A = B) or (C> A) is true, not this here: (A = B) or (C> A)
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will return me the False value!
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So what he did was the following: A is equal to B? , no! C is higher qua A ?, yes!
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False or true is: true and not true is: false.
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And again, you will be able to do your logical and relational tests,
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using: numbers, variables or expressions.
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Remembering that to use logical operators, you can only test logical values.
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And remember, too, that all expressions using relational operators generate logical results.
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What I recommend is that you make several logical tests
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like the one I just used.
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then do tests and try to find out what is the logical result at the end.
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if you prefer to pause the video at that point back to your visual g and do some testing,
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and do not forget to put all your relational comparisons between parenthesis
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because they are going to generate the logical results at the end
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and speaking in parenthesis we have to be concerned enough with the order of precedence
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we saw in the previous lesson that there is an order of precedence between the arithmetic operators
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now that we have seen the two other operators, relational and logical
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we will see a general table of how the order of precedence in expressions containing
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arithmetic, logical and relational operations
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therefore, we understand how to work the general order of precedence
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an expression that has arithmetic, relational and logical operators at the same time
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First, the arithmetic will be made
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giving in order of precedence, we have seen previously
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the parentheses, then exponentiation, soon after, multiplication and division, and finally, the additions and subtractions
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after all arithmetic expressions are resolved
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They will be held all relational operations
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within the relational operators, which are "higher," "lower," "greater than or equal", "less than or equal", "equal" and different
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Everyone has the same order of precedence, and will always run from left to right
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Finally, after being solved the arithmetic expressions and relational
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execute all logical operations
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starting with 'E', soon after the 'OR' and finally the 'NO'
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save this table in your mind, this is the execution order of all the operators that can be used within an algorithm
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Now it's easy right ?!
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Now we have gathered all the information about operators, you can now go for something bigger
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which is a more complex exercise using relational and logical arithmetic operators
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along with the input commands and output that we have seen previously
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let's think then in an exercise that uses all that we've seen so far, including the variables
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let's make an example that later will be more complete
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but for now since the work for us
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I'm going to do is this, surely you know triangles
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what I will do here is to read three sides of a triangle, which I'll call L1, L2 and L3
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These values will be real ( 'L1, L2, L3: Real'). And I'll make a logical test to see if this triangle can be equilateral or scalene.
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WHAT will lead me into a logical test ( 'logical')
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if you remember the triangles study equilateral triangle is one that has three equal sides
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the scalene triangle is one that has three different sides
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for now I will not worry if the three values that were actually typed form a triangle
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because there is a mathematical rule for this. But with us 'ok' at first, we will not see this mathematical rule yet.
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We will see later on in a more complex exercise.
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in fact, we read three values and see if they are totally equal to each other,
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or completely different.
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we do the testing here and understand how the relational and logical operators work
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so here, vamomos start asking the user to enter the three sides
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Write ( "enter the first side")
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Read (L1)
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I will do the same for the other two sides
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the procedure is exactly the same
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only the read will play the value in another variable
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Finally, I will do so with the third. Read (L3)
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now I've done three of reading
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what I will do is to check if the triangle is equilateral
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EQ will receive the logical outcome of the tests of the three sides ( 'EQ 00:20:38,280
it is checking whether the triangle will be equilateral
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or scalene
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we will do some tests
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running
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First side 3
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second side
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two
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third side
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4
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three two four
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are three different values each other
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soon
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would form
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a scalene triangle
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let's check
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the equilateral triangle can not be
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but it can be scalene
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let's go back.
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rerun
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and we put 4, 4:04
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which form an equilateral triangle
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The triangle is equilateral? true.
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The triangle is scalene? false.
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Let's do another test
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it will be four (4) four (4) and three (3)
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Here, we have two equal sides and a different
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What would lead me an isosceles triangle.
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We are not testing in this case
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But it will be neither equilateral nor scalene ..
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The logical result:
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The triangle is equilateral? False
The triangle is scalene? False
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And just remember what I said
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There is a mathematical rule
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To verify that the three sides can form a triangle
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And this logical test is simple
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Each side must be less than the sum of the other two sides
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So if I have side L1, L2 and L3
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L1 must be less than the sum of the other two
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L2 must be smaller than the sum of the other two
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And L3 must also be less than the sum of the other two.
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And note that I used the logical operator "and" in my sentence
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So let's create another logical variable to see if it can be a triangle.
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Then I'll create a new logical value called "TRI".
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That will determine whether it can be a triangle
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My variable "TRI" will receive the logical result
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L1, is less than the sum of L2 to L3
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Note here that this expression
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the arithmetic operators have higher precedence, according to the table that we saw,
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then he will do first L2 + L3,
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and test whether the sum between the two is greater than L1
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I also have to take the tests
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between L2 is greater than L1 + L3
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And also you have to know if L3 is smaller than L1 + L2.
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A triangle can only exist if all these operations result in a true logical value.
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We will show here
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Escreval "can form a Tiângulo?"
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we'll see whether or not
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with the amount of IRT
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Let's do some more tests
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if I put 2, 2:02,
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It can form a triangle, it forms an equilateral triangle and does not form a scalene.
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Another test:
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That 2, 3 and 4 we saw earlier,
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it can form a triangle, not an equilateral triangle, but may form a scalene triangle
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Let's do one more test:
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That our 2, 2 and 3.
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it can form a triangle, but it can not be equilateral or scalene
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this because it is an isosceles triangle.
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Finally, let's do a test with 2, 2:05.
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2, 2 and 5 can not make a triangle,
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because 2 is less than + 5 2 7 which is
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2 here is less than 5 + 2 that is 7,
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5 but it is not lower than 2 which is 4 + 2.
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Then the third side would be too large to form a triangle.
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So, in the case here, the logical result would be, he can not form a triangle,
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It can not be equilateral and scalene less.
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And then you can ask me, "But Guanabara, we have two equal sides and 1 different,
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it would be isosceles right? "
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No! Because of 5, 2 and 2a can not form a triangle,
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and we see that for this result I just mark
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You get the idea? We will return to this our reasoning about triangles,
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later, when we go see relational operators
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But for now, our time is up, and we'll have to leave for our next class,
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that only comes out next week. In the next lecture I will show a new tool, in addition to VisuAlg,
00:24:49
it is much easier for you to learn algorithms.
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But it is not so professional.
00:24:54
If you downloaded the package here in www.cursoemvideo.com,
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surely you already have the Scratch application. I do not know if you have already installed.
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Install as the next class we will use it,
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and you will see that you will have great fun with this tool,
00:25:08
And will, break, learn a lot of Logic Programming.
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Again I wanted to ask first: Practice!
00:25:15
Second, work with the course of the project in Video.
00:25:18
By clicking here, you sign the channel and will receive all the information whenever you have a new class,
00:25:23
Side button "Sign" has a gear,
00:25:26
click it, and say you want to receive an email whenever you leave a new class, so you will not miss anything.
00:25:31
By clicking here, you will watch all algorithm course lectures so far,
00:25:36
so if you come now, it is welcome, but you have some previous classes,
00:25:40
to be able to understand the construction of algorithms, and I recommend you click here and watch them all.
00:25:45
Do not forget to always share classes give Joinha in the videos,
00:25:49
Share to your Facebook, get there on Facebook and tell your friends pros: "Look!
00:25:53
Watch this lesson here. learn to program! "
00:25:55
We are here in the first steps to building algorithms,
00:25:58
and surely you will learn how to program.
00:26:01
I'll show various tools, I will show several techniques,
00:26:04
I will always teach you a rhythm a little more well cadenced,
00:26:09
for you to understand algorithms, for you to build algorithms.
00:26:13
Up to me to teach you, and I'm doing my part.
00:26:16
It depends on you learn, for that you need to practice.
00:26:19
Never forget. Study hard, a big hug and see you soon!
00:26:25
Hi! Someone came clattering hell.
00:26:29
I said fighting with you! Alas, alas, alas!
00:26:32
I really wanted the phone that damn who is calling at 8 am inside the company!
