indexing description: "Pseudo-random number sequence, linear congruential method" names: random class interface RANDOM create make -- Initialize structure using a default seed. ensure seed_set: seed = default_seed set_seed (s: INTEGER) -- Initialize sequence using s as the seed. require non_negative: s >= 0 ensure seed_set: seed = s feature -- Initialization make -- Initialize structure using a default seed. ensure seed_set: seed = default_seed set_seed (s: INTEGER) -- Initialize sequence using s as the seed. require non_negative: s >= 0 ensure seed_set: seed = s feature -- Access default_seed: INTEGER -- Default value 123,457; -- may be redefined for a new generator. double_i_th (i: INTEGER): DOUBLE -- The i-th random number as a double between 0 and 1 double_item: DOUBLE -- The current random number as a double between 0 and 1 has (n: INTEGER): BOOLEAN -- Will n be part of the random number sequence? ensure -- from CONTAINER not_found_in_empty: Result implies not empty ensure then only_: Result = (n < modulus and n >= 0) i_th (i: INTEGER): INTEGER -- The i-th random number require -- from COUNTABLE positive_argument: i > 0 ensure then in_range: (Result < modulus) and (Result >= 0) increment: INTEGER -- Default value 0; -- may be redefined for a new generator. index: INTEGER -- Index of current position -- (from COUNTABLE_SEQUENCE) index_of (v: like item; i: INTEGER): INTEGER -- Index of i-th occurrence of v. -- 0 if none. -- (Reference or object equality, -- based on object_comparison.) -- (from LINEAR) require -- from LINEAR positive_occurrences: i > 0 ensure -- from LINEAR non_negative_result: Result >= 0 item: INTEGER -- Item at current position -- (from COUNTABLE_SEQUENCE) require -- from ACTIVE readable: readable require -- from TRAVERSABLE not_off: not off modulus: INTEGER -- Default value 2^31 -1 = 2,147,483,647; -- may be redefined for a new generator. multiplier: INTEGER -- Default value 7^5 = 16,807; -- may be redefined for a new generator. next_random (n: INTEGER): INTEGER -- Next random number after n -- in pseudo-random order require in_range: (n < modulus) and (n >= 0) ensure in_range: (Result < modulus) and (Result >= 0) occurrences (v: INTEGER): INTEGER -- Number of times v appears. -- (Reference or object equality, -- based on object_comparison.) -- (from LINEAR) ensure -- from BAG non_negative_occurrences: Result >= 0 real_i_th (i: INTEGER): REAL -- The i-th random number as a real between 0 and 1 real_item: REAL -- The current random number as a real between 0 and 1 search (v: like item) -- Move to first position (at or after current -- position) where item and v are equal. -- (Reference or object equality, -- based on object_comparison.) -- If no such position ensure that exhausted will be true. -- (from LINEAR) ensure -- from LINEAR object_found: (not exhausted and object_comparison) implies equal (v, item); item_found: (not exhausted and not object_comparison) implies v = item seed: INTEGER -- Seed for sequence. feature -- Status report After: BOOLEAN is false -- Is current position past last item? (Answer: no.) -- (from COUNTABLE_SEQUENCE) changeable_comparison_criterion: BOOLEAN -- May object_comparison be changed? -- (Answer: yes by default.) -- (from CONTAINER) Empty: BOOLEAN is false -- Is structure empty? (Answer: no.) -- (from INFINITE) exhausted: BOOLEAN -- Has structure been completely explored? -- (from LINEAR) ensure -- from LINEAR exhausted_when_off: off implies Result Extendible: BOOLEAN is false -- May items be added? (Answer: no.) -- (from COUNTABLE_SEQUENCE) Full: BOOLEAN is true -- The structure is complete -- (from INFINITE) object_comparison: BOOLEAN -- Must search operations use equal rather than = -- for comparing references? (Default: no, use =.) -- (from CONTAINER) off: BOOLEAN -- Is there no current item? -- (from LINEAR) Prunable: BOOLEAN is false -- May items be removed? (Answer: no.) -- (from COUNTABLE_SEQUENCE) Readable: BOOLEAN is true -- Is there a current item that may be read? -- (Answer: yes.) -- (from COUNTABLE_SEQUENCE) Writable: BOOLEAN is false -- Is there a current item that may be written? -- (Answer: no.) -- (from COUNTABLE_SEQUENCE) feature -- Status setting compare_objects -- Ensure that future search operations will use equal -- rather than = for comparing references. -- (from CONTAINER) require -- from CONTAINER changeable_comparison_criterion ensure -- from CONTAINER object_comparison compare_references -- Ensure that future search operations will use = -- rather than equal for comparing references. -- (from CONTAINER) require -- from CONTAINER changeable_comparison_criterion ensure -- from CONTAINER reference_comparison: not object_comparison feature -- Cursor movement forth -- Move to next position. -- (from COUNTABLE_SEQUENCE) require -- from LINEAR not_after: not after start -- Move to first position. -- (from COUNTABLE_SEQUENCE) invariant -- from GENERAL reflexive_equality: standard_is_equal (Current); reflexive_conformance: conforms_to (Current); non_negative_seed: seed >= 0; non_negative_increment: increment >= 0; positive_multiplier: multiplier > 0; modulus_constraint: modulus > 1; -- from INFINITE never_empty: not empty; always_full: full; -- from ACTIVE writable_constraint: writable implies readable; empty_constraint: empty implies (not readable) and (not writable); -- from LINEAR after_constraint: after implies off; -- from TRAVERSABLE empty_constraint: empty implies off; end -- class RANDOM