Several built-in, infix operators allow testing for equality and inequality. For numbers, <, >, <=, >=, ==, and != are used. For strings, eq, neq, and like are used.
The following are all valid predicate expressions:
c == 5
page:var("city") eq "Blackfoot"
"Lindon" neq location:city()
weather:curr_temp() < 90
location:city() + ", WA" eq city
5 * (weather:curr_temp() - 32) / 9 < 0 |
As can be seen from the preceding examples, a number of built-in libraries provide predicates that can be used inside predicate expressions. The documentation for those libraries gives details about their operation.
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 |
Like takes a regular expression as its second argument and returns true if it matches the string given as its first argument. Arguments to these operators can be any valid expression.
spicy = cheese like re/(nacho|pepperjack)/; |
Note that when the |
There is an infix operator for testing membership, ><. The >< operator tests the number or string in the right operand for membership in the map or array given by the left operand. For maps, membership extends to keys only.
a = [5, 6, 7];
m = {"a" : 1, "b" : 2};
a >< 6 // returns true
a >< 3 // returns false
m >< "a" // returns true
m >< "foo" // returns false |
Compound predicate expressions are created using the operators &&, ||, and not to express conjunction, disjunction, and negation, respectively. Conjunction has precedence over disjunction. Parentheses are used to group expressions for precedence.
not a a && b a || b (a || b ) && not c |