Definition: integer i = compare(object x1, object x2)
Description: Return 0 if objects x1 and x2 are identical, 1 if x1 is greater than x2, -1 if x1 is less than x2. Atoms are considered to be less than sequences. Sequences are compared "alphabetically" starting with the first element until a difference is found.

Note that RDS Eu/OpenEuphoria typically need equal() or compare() on each and every non-trivial conditional test, whereas phix does not and can use =, <=, etc. Apart from the obvious legacy code and compatibility with RDS Eu/OpenEuphoria, compare is also very useful in sort routines and the like.
Example 1:
x = compare({1,2,{3,{4}},5}, {2-1,1+1,{3,{4}},6-1})
-- identical, x is 0
Example 2:
if compare("ABC", "ABCD") < 0 then   -- -1
    -- will be true: ABC is "less" because it is shorter
end if
Example 3:
x = compare({12345, 99999, -1, 700, 2},
            {12345, 99999, -1, 699, 3, 0})
-- x will be 1 because 700 > 699
Example 4:
x = compare('a', "a")
-- x will be -1 because 'a' is an atom
-- while "a" is a sequence
Implementation: Implemented as %opScmp in builtins\VM\pJcc.e (an autoinclude) - be warned however it is low-level complicated stuff that you do not need to know.
See Also: equal, min, max, relational operators, sequence operations