Page Comparison

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Two special comparison operators are useful with the sort() operator: <=> and cmp. These operators return -1 if the first operand is less than the second, 0, if they're equal, and 1 if the first operand is greater than the second. The <=> operator is used with numbers and cmp is used with strings.

x = 5; 
y = 6;
x <=> y // returns -1
x <=> x // returns 0
y <=> x // returns 1
p = "aab";
q = "abb";
a cmp b // returns -1
a cmp a // returns 0
b cmp a // returns 1

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not a
a && b
a || b
(a || b ) && not c

The operators && and || use short-circuit evaluation semantics. 

val = arg || default

In the example code shown above, the name val is bound to the value of arg provided it is considered to be "true" and otherwise binds it to the value of default. This is similar to, but more general than, the universal operator defaultsTo except that the latter only applies when the value it is operating on is specifically null.