Class REAL

5.9 Class REAL

indexing

description: "Real values, simple precision"

expanded class interface

REAL

feature -- Access

hash_code: INTEGER
        -- 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 = 1.0

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 = 0.0

feature -- Comparison

infix "<" (other: like Current): BOOLEAN
        -- Is other greater than current real?
        -- (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
        not_exact_zero: Result implies (other /= 0.0)

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 (0) or 
            (other.conforms_to (Current) and (Current >= 0.0)))
                implies Result

feature -- Conversion

ceiling: INTEGER
        -- Smallest integral value no smaller than current object
    ensure
        result_no_smaller: Result >= Current;
        close_enough: Result - Current < one

floor: INTEGER
        -- Greatest integral value no greater than current object
    ensure
        result_no_greater: Result <= Current;
        close_enough: Current - Result < one

rounded: INTEGER
        -- Rounded integral value
    ensure
        definition: Result = sign * ((abs + 0.5).floor)

truncated_to_integer: INTEGER
        -- Integer part (same sign, largest absolute
        -- value no greater than current object's)

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
    ensure
        result_exists: Result /= 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): like Current
        -- Division by other
        -- (From NUMERIC.)
    require
        other_exists: other /= Void;
        good_divisor: divisible (other)
    ensure
        result_exists: Result /= Void

infix "^" (other: NUMERIC): DOUBLE
        -- Current real to power 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 real value
        -- (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