Comparison operators

Comparison operators compare values with each other and return true or false to indicate whether relationship between them holds.

@> [1 = 1, 1 != 1, 1 < 1, 1 > 1, 1 <= 1, 1 >= 1]@> [1 = 2, 1 != 2, 1 < 2, 1 > 2, 1 <= 2, 1 >= 2]@> [3 = 2, 3 != 2, 3 < 2, 3 > 2, 3 <= 2, 3 >= 2]

Note that false is the empty set, so it displays as {}. Also, while true is actually {()} it displays as true because it is almost never used to mean something else.

Set comparisons

A related and more extensive set of operators is available for set comparisons. These operators determine subset and superset relationships rather than strict less/greater ordering.

@> {} (<) {1, 2}@> {1, 2} !(<) {}@> {1, 2} !(<=) {}@> {1, 2} !(<) {1, 2}@> {1, 2} (<=) {1, 2}@> {1, 2} !(<>=) {1, 3}

The general form is an optional ! denoting "not" followed by any combination of <, > and =, denoting "is subset of", "is superset of" and "equals", respectively.

In addition to comparing sets, you can test set membership:

@> 2 <: {1, 2, 3}@> 4 !<: {1, 2, 3}@> {2, 3} <: {1, 2, 3, 4}@> {2, 3} <: {1, {2, 3}, 4}

Note that these operators may not work the way you expect with sugared syntax such as strings and arrays. Remember that the values are being compared very literally, down the the index (@) of the element. For example:

@>   "o" (<) "hello"       # false@> 4\"o" (<) "hello"       # true@> [1] (<) [1, 2, 3]       # true@> [2] (<) [1, 2, 3]       # false@> [1, , 3] (<) [1, 2, 3]  # true