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operator 1

What does the following program print?

package main

var x, y = true, false

func o(b bool) bool {
	print(b)
	return !b
}

func main() {
	_ = x || o(x)
	_ = y && o(y)
}

Choices:

true
false
truefalse
(It prints nothing)

Answer: (It prints nothing)

Run it on Go play.

Key points:

When evaluating a || b, the expression a is evaluated firstly and the expression b will be only evaluated if a is evaluated as false.
When evaluating a && b, the expression a is evaluated firstly and the expression b will be only evaluated if a is evaluated as true.

(more articles ↡)

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Articles in this book:

slice: 1, 2, 3
map: 1
channel: 1
loop: 1, 2, 3, 4
switch: 1
defer: 1, 2
panic/recover: 1, 2
reflect: 1, 2
const: 1, 2, 3, 4, 5
operator: 1, 2, 3
function call: 1
scope: 1, 2
nil: 1
embedding: 1

(more are coming ...)