A value of type bool, or boolean, has only two possible values,
true and false.
The conditions in if and for statements are booleans, and comparison
operators like == and < produce a boolean result. The unary operator ! is
logical negation, so !true is false, or, one might say,
(!true==false)==true, although as a matter of style, we always
simplify redundant boolean expressions like x==true to x.
Boolean values can be combined with the && (AND) and || (OR)
operators, which have short-circuit behavior: if the answer is
already determined by the value of the left operand, the right operand
is not evaluated, making it safe to write expressions like this:
s != "" && s[0] == 'x'
where s[0] would panic if applied to an empty string.
Since && has higher precedence than ||
(mnemonic: && is boolean
multiplication, || is boolean addition), no parentheses are required for
conditions of this form:
if 'a' <= c && c <= 'z' ||
'A' <= c && c <= 'Z' ||
'0' <= c && c <= '9' {
// ...ASCII letter or digit...
}
There is no implicit conversion from a boolean value to a numeric value like 0 or
1, or vice versa. It’s necessary to use an explicit if, as in
i := 0
if b {
i = 1
}
It might be worth writing a conversion function if this operation were needed often:
// btoi returns 1 if b is true and 0 if false.
func btoi(b bool) int {
if b {
return 1
}
return 0
}
The inverse operation is so simple that it doesn’t warrant a function, but for symmetry here it is:
// itob reports whether i is non-zero.
func itob(i int) bool { return i != 0 }