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105 lines
2.7 KiB
Markdown
105 lines
2.7 KiB
Markdown
# Boolean
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true or false.
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A Boolean has one of two possible values: `true`; `false`. Boolean (logical) operators (*and*, *or*, *not*) take Boolean inputs and yields a Boolean value. Comparison operators on other types ([numbers](/reference/types/number), [strings](/reference/types/string) yields a Boolean value.
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The following blocks represent the true and false Boolean values, which can be plugged in anywhere a Boolean value is expected:
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```blocks
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true;
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false;
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```
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The next three blocks represent the three Boolean (logic) operators:
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```blocks
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true && false;
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true || false;
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!true;
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```
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The next six blocks represent comparison operators that yield a Boolean value. Most comparisons you will do involve [numbers](/reference/types/number):
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```blocks
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42 == 0;
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42 != 0;
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42 < 0;
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42 > 0;
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42 <= 0;
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42 >= 0;
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```
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Boolean values and operators are often used with an [if](/blocks/logic/if) or [while](/blocks/loops/while) statement to determine which code will execute next. For example:
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### Functions that return a Boolean
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Some functions return a Boolean value, which you can store in a Boolean variable. For example, the following code gets the on/off state of `point (1, 2)` and stores this in the Boolean variable named `on`. Then the code clears the screen if `on` is `true`:
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### Boolean operators
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Boolean operators take Boolean inputs and evaluate to a Boolean output:
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### Conjunction: `A and B`
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`A and B` evaluates to `true` if-and-only-if both A and B are true:
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```blocks
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false && false == false;
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false && true == false;
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true && false == false;
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true && true == true;
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```
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### Disjunction: `A or B`
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`A or B` evaluates to `true` if-and-only-if either A is true or B is true:
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```blocks
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false || false == false;
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false || true == true;
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true || false == true;
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true || true == true;
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```
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### Negation: `not A`
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`not A` evaluates to the opposite (negation) of A:
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```blocks
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!false == true;
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!true == false;
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```
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### Example
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This example turns on LED `3 , 3`, if LEDs `1 , 1` and `2 , 2` are both on:
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```blocks
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if (led.point(1,1) && led.point(2,2)) {
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led.plot(3,3)
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}
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```
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### Comparisons of numbers and strings
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When you compare two Numbers, you get a Boolean value, such as the comparison `x < 5` in the code below:
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```blocks
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input.onButtonPressed(Button.A, () => {
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let x = Math.random(5)
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if(x < 5) {
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basic.showString("low");
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} else {
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basic.showString("high");
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}
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})
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```
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See the documentation on [Numbers](/reference/types/number) for more information on comparing two Numbers. You can also [compare strings](/reference/types/string-functions) using the `equals` function.
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### See also
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[if](/blocks/logic/if), [while](/blocks/loops/while), [number](/reference/types/number)
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