92b60a251d
* annotating APIs to support onstart * missed file * updated templates * adding new lines in main.ts * fixing docs * removing onstart * updated docs * updated various docs * more docs * adding upgrade policies for blocks * updated pxt reference * placing on start under "basic"
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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, strings 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:
true;
false;
The next three blocks represent the three Boolean (logic) operators:
true && false;
true || false;
!true;
The next six blocks represent comparison operators that yield a Boolean value. Most comparisons you will do involve numbers:
42 == 0;
42 != 0;
42 < 0;
42 > 0;
42 <= 0;
42 >= 0;
Boolean values and operators are often used with an if or 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:
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:
false || false == false;
false || true == true;
true || false == true;
true || true == true;
Negation: not A
not A evaluates to the opposite (negation) of A:
!false == true;
!true == false;
Example
This example turns on LED 3 , 3, if LEDs 1 , 1 and 2 , 2 are both on:
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:
input.onButtonPressed(Button.A, () => {
let x = Math.random(5)
if(x < 5) {
basic.showString("low");
} else {
basic.showString("high");
}
})
See the documentation on Numbers for more information on comparing two Numbers. You can also compare strings using the equals function.