Class INTEGER

5.8 Class INTEGER

indexing

description: "Integer values"

expanded class interface

INTEGER

feature -- Access

hash_code: INTEGER is
        -- Hash code value
        -- (From HASHABLE.)
    ensure
        good_hash_value: Result >= 0

one: like Current
        -- Neutral element for "*" and "/"
        -- (From NUMERIC.)
    ensure
        Result_exists: Result /= Void;
        value: Result = 1

sign: INTEGER
        -- Sign value (0, -1 or 1)
    ensure
        three_way: Result = three_way_comparison (zero)

zero: like Current
        -- Neutral element for "+" and "-"
        -- (From NUMERIC.)
    ensure
        Result_exists: Result /= Void;
        value: Result = 0

feature -- Comparison

infix "<" (other: like Current): BOOLEAN
        -- Is other greater than current integer?
        -- (From COMPARABLE.)
    require
        other_exists: other /= Void
    ensure
        asymmetric: Result implies not (other < Current)

infix "<=" (other: like Current): BOOLEAN
        -- Is current object less than or equal to other?
        -- (From COMPARABLE.)
    require
        other_exists: other /= Void
    ensure
        definition: Result = (Current < other) or is_equal (other);

infix ">=" (other: like Current): BOOLEAN
        -- Is current object greater than or equal to other?
        -- (From COMPARABLE.)
    require
        other_exists: other /= Void
    ensure
        definition: Result = (other <= Current)

infix ">" (other: like Current): BOOLEAN
        -- Is current object greater than other?
        -- (From COMPARABLE.)
    require
        other_exists: other /= Void
    ensure
        definition: Result = (other < Current)

max (other: like Current): like Current
        -- The greater of current object and other
        -- (From COMPARABLE.)
    require
        other_exists: other /= Void
    ensure
        current_if_not_smaller: (Current >= other) implies (Result = Current)
        other_if_smaller: (Current < other) implies (Result = other)

min (other: like Current): like Current
        -- The smaller of current object and other
        -- (From COMPARABLE.)
    require
        other_exists: other /= Void
    ensure
        current_if_not_greater: (Current <= other) implies (Result = Current)
        other_if_greater: (Current > other) implies (Result = other)

three_way_comparison (other: like Current): INTEGER
        -- If current object equal to other, 0; if smaller,
        -- -1; if greater, 1.
        -- (From COMPARABLE.)
    require
        other_exists: other /= Void
    ensure
        equal_zero: (Result = 0) = is_equal (other);
        smaller: (Result = 1) = Current < other;
        greater_positive: (Result = -1) = Current > other

feature -- Status report

divisible (other: like Current): BOOLEAN
        -- May current object be divided by other?
        -- (From NUMERIC.)
    require
        other_exists: other /= Void
    ensure
        value: Result = (other /= 0)

exponentiable (other: NUMERIC): BOOLEAN
        -- May current object be elevated to the power other?
        -- (From NUMERIC.)
    require
        other_exists: other /= Void
    ensure
        safe_values: (other.conforms_to (Current) or 
            (other.conforms_to (0.0) and (Current >= 0)))
                implies Result

feature -- Basic operations

abs: like Current
        -- Absolute value
    ensure
        non_negative: Result >= 0;
        same_absolute_value: (Result = Current) or (Result = - Current)

infix "*" (other: like Current): like Current
        -- Product by other
        -- (From NUMERIC.)
    require
        other_exists: other /= Void

infix "+" (other: like Current): like Current
        -- Sum with other
        -- (From NUMERIC.)
    require
        other_exists: other /= Void
    ensure
        result_exists: Result /= Void;
        commutative: equal (Result, other + Current)

infix "-" (other: like Current): like Current
        -- Result of subtracting other
        -- (From NUMERIC.)
    require
        other_exists: other /= Void
    ensure
        result_exists: Result /= Void

infix "/" (other: like Current): DOUBLE
        -- Division by other
    require
        other_exists: other /= Void;
        good_divisor: divisible (other)
    ensure
        result_exists: Result /= Void

infix "//" (other: like Current): like Current
        -- Integer division of Current by other
        -- (From "/" in NUMERIC.)
    require
        other_exists: other /= Void;
        good_divisor: divisible (other)
    ensure
        result_exists: divisible (other)

infix "\\" (other: like Current): like Current
        -- Remainder of the integer division of Current by other
    require
        other_exists: other /= Void;
        good_divisor: divisible (other)
    ensure
        result_exists: Result /= Void

infix "^" (other: NUMERIC): DOUBLE
        -- Integer power of Current by other
        -- (From NUMERIC.)
    require
        other_exists: other /= Void;
        good_exponent: exponentiable (other)
    ensure
        result_exists: Result /= Void

prefix "+": like Current
        -- Unary plus
        -- (From NUMERIC.)
    ensure
        result_exists: Result /= Void

prefix "-": like Current
        -- Unary minus
        -- (From NUMERIC.)
    ensure
        result_exists: Result /= Void

feature -- Output

out: STRING
        -- Printable representation of current object
        -- (From GENERAL.)

invariant

irreflexive_comparison: not (Current < Current);
neutral_addition: equal (Current + zero, Current);
self_subtraction: equal (Current - Current, zero);
neutral_multiplication: equal (Current * one, Current);
self_division: divisible (Current) implies equal (Current / Current, one)
sign_times_abs: equal (sign * abs, Current)

end