4.1.5 Comparing Values

Any two values can be compared for equality using `==' and `!='. The first of these returns 1 if the two values are equal and 0 otherwise; the second does the reverse:

3 == 4 => 0 3 != 4 => 1 3 == 3.0 => 0 "foo" == "Foo" => 1 #34 != #34 => 0 {1, #34, "foo"} == {1, #34, "FoO"} => 1 E_DIV == E_TYPE => 0 3 != "foo" => 1

Note that integers and floating-point numbers are never equal to one another, even in the `obvious' cases. Also note that comparison of strings (and list values containing strings) is case-insensitive; that is, it does not distinguish between the upper- and lower-case version of letters. To test two values for case-sensitive equality, use the `equal' function described later.

Warning: It is easy (and very annoying) to confuse the equality-testing operator (`==') with the assignment operator (`='), leading to nasty, hard-to-find bugs. Don't do this.

Numbers, object numbers, strings, and error values can also be compared for ordering purposes using the following operators:

< <= >= >

meaning "less than," "less than or equal," "greater than or equal," and "greater than," respectively. As with the equality operators, these return 1 when their operands are in the appropriate relation and 0 otherwise:

3 < 4 => 1 3 < 4.0 error--> E_TYPE #34 >= #32 => 1 "foo" <= "Boo" => 0 E_DIV > E_TYPE => 1

Note that, as with the equality operators, strings are compared case-insensitively. To perform a case-sensitive string comparison, use the `strcmp' function described later. Also note that the error values are ordered as given in the table in the section on values. If the operands to these four comparison operators are of different types (even integers and floating-point numbers are considered different types), or if they are lists, then E_TYPE is raised.