103 lines
2.6 KiB
Markdown
103 lines
2.6 KiB
Markdown
# Boolean
|
|
|
|
true or false.
|
|
|
|
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.
|
|
|
|
The following blocks represent the true and false Boolean values, which can be plugged in anywhere a Boolean value is expected:
|
|
|
|
```blocks
|
|
true;
|
|
false;
|
|
```
|
|
|
|
The next three blocks represent the three Boolean (logic) operators:
|
|
|
|
```blocks
|
|
true && false;
|
|
true || false;
|
|
!true;
|
|
```
|
|
|
|
The next six blocks represent comparison operators that yield a Boolean value. Most comparisons you will do involve [numbers](/reference/types/number):
|
|
|
|
```blocks
|
|
42 == 0;
|
|
42 != 0;
|
|
42 < 0;
|
|
42 > 0;
|
|
42 <= 0;
|
|
42 >= 0;
|
|
```
|
|
|
|
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:
|
|
|
|
### Functions that return a Boolean
|
|
|
|
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`:
|
|
|
|
### Boolean operators
|
|
|
|
Boolean operators take Boolean inputs and evaluate to a Boolean output:
|
|
|
|
### Conjunction: `A and B`
|
|
|
|
`A and B` evaluates to `true` if-and-only-if both A and B are true:
|
|
|
|
```blocks
|
|
false && false == false;
|
|
false && true == false;
|
|
true && false == false;
|
|
true && true == true;
|
|
```
|
|
|
|
### Disjunction: `A or B`
|
|
|
|
`A or B` evaluates to `true` if-and-only-if either A is true or B is true:
|
|
|
|
```blocks
|
|
false || false == false;
|
|
false || true == true;
|
|
true || false == true;
|
|
true || true == true;
|
|
```
|
|
|
|
### Negation: `not A`
|
|
|
|
`not A` evaluates to the opposite (negation) of A:
|
|
|
|
```blocks
|
|
!false == true;
|
|
!true == false;
|
|
```
|
|
|
|
### Example
|
|
|
|
This example turns on LED `3 , 3`, if LEDs `1 , 1` and `2 , 2` are both on:
|
|
|
|
```blocks
|
|
if (led.point(1,1) && led.point(2,2)) {
|
|
led.plot(3,3)
|
|
}
|
|
```
|
|
|
|
### Comparisons of numbers and strings
|
|
|
|
When you compare two Numbers, you get a Boolean value, such as the comparison `x < 5` in the code below:
|
|
|
|
```blocks
|
|
let x = Math.random(5)
|
|
if(x < 5) {
|
|
basic.showString("low");
|
|
} else {
|
|
basic.showString("high");
|
|
}
|
|
```
|
|
|
|
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.
|
|
|
|
### See also
|
|
|
|
[if](/blocks/logic/if), [while](/blocks/loops/while), [number](/reference/types/number)
|
|
|