note description: "[ Finite sequences of some elements of type G. A valid index is 1..count. Array notation can be used, as well as iteration (across). Empty sequences can be created, or creation can be from an array. Sequences have a first item (the head), a tail and last item. Infix notation for prepended_by where x is of generic type G: seq1 |< x Infix notation for appended_by where x is of generic type G: seq1 |> x For concatenation we use infix: seq1 |++| seq2 For queries, to assert that the state is not changed, the postcondition is Current ~ old Current.deep_twin Class also has an inefficient implementation: ]" author: "JSO" date: "$Date$" revision: "$Revision$" class interface SEQ [G -> attached ANY] create make_empty -- create empty list ensure is_empty: is_empty make_from_array (a: ARRAY [G]) -- Create list from array a. ensure # Current = a.count across a.lower |..| a.upper as i all Current [i.item - a.lower + 1] ~ a [i.item] end convert make_from_array ({ARRAY [G]}), make_from_array: {ARRAY [G]} feature -- Access generating_type: TYPE [detachable SEQ [G]] -- Type of current object -- (type of which it is a direct instance) -- (from ANY) ensure -- from ANY generating_type_not_void: Result /= Void generator: STRING_8 -- Name of current object's generating class -- (base class of the type of which it is a direct instance) -- (from ANY) ensure -- from ANY generator_not_void: Result /= Void generator_not_empty: not Result.is_empty feature -- Comparison frozen deep_equal (a: detachable ANY; b: like arg #1): BOOLEAN -- Are a and b either both void -- or attached to isomorphic object structures? -- (from ANY) ensure -- from ANY instance_free: class shallow_implies_deep: standard_equal (a, b) implies Result both_or_none_void: (a = Void) implies (Result = (b = Void)) same_type: (Result and (a /= Void)) implies (b /= Void and then a.same_type (b)) symmetric: Result implies deep_equal (b, a) frozen equal (a: detachable ANY; b: like arg #1): BOOLEAN -- Are a and b either both void or attached -- to objects considered equal? -- (from ANY) ensure -- from ANY instance_free: class definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.is_equal (b)) frozen is_deep_equal (other: SEQ [G]): BOOLEAN -- Are Current and other attached to isomorphic object structures? -- (from ANY) require -- from ANY other_not_void: other /= Void ensure -- from ANY shallow_implies_deep: standard_is_equal (other) implies Result same_type: Result implies same_type (other) symmetric: Result implies other.is_deep_equal (Current) frozen standard_equal (a: detachable ANY; b: like arg #1): BOOLEAN -- Are a and b either both void or attached to -- field-by-field identical objects of the same type? -- Always uses default object comparison criterion. -- (from ANY) ensure -- from ANY instance_free: class definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.standard_is_equal (b)) frozen standard_is_equal (other: SEQ [G]): BOOLEAN -- Is other attached to an object of the same type -- as current object, and field-by-field identical to it? -- (from ANY) require -- from ANY other_not_void: other /= Void ensure -- from ANY same_type: Result implies same_type (other) symmetric: Result implies other.standard_is_equal (Current) feature -- Status report conforms_to (other: ANY): BOOLEAN -- Does type of current object conform to type -- of other (as per Eiffel: The Language, chapter 13)? -- (from ANY) require -- from ANY other_not_void: other /= Void same_type (other: ANY): BOOLEAN -- Is type of current object identical to type of other? -- (from ANY) require -- from ANY other_not_void: other /= Void ensure -- from ANY definition: Result = (conforms_to (other) and other.conforms_to (Current)) feature -- Conversion as_array: ARRAY [G] -- Return current sequence as an array ensure current_set_unchanged: Current ~ old Current.deep_twin Result.lower = 1 Result.upper = count across 1 |..| count as pos all Current [pos.item] ~ Result [pos.item] end as_function: FUN [INTEGER_32, G] -- Return current sequence as a function -- with its domain being the set of positions ensure current_set_unchanged: Current ~ old Current.deep_twin all_positions_included: # Result.domain = # Current across Result.domain as pos all valid_position (pos.item) end across Result.domain as pos all Current [pos.item] ~ Result [pos.item] end feature -- Duplication copy (other: SEQ [G]) -- Update current object using fields of object attached -- to other, so as to yield equal objects. -- (from ANY) require -- from ANY other_not_void: other /= Void type_identity: same_type (other) ensure -- from ANY is_equal: Current ~ other frozen deep_copy (other: SEQ [G]) -- Effect equivalent to that of: -- copy (other . deep_twin) -- (from ANY) require -- from ANY other_not_void: other /= Void ensure -- from ANY deep_equal: deep_equal (Current, other) frozen deep_twin: SEQ [G] -- New object structure recursively duplicated from Current. -- (from ANY) ensure -- from ANY deep_twin_not_void: Result /= Void deep_equal: deep_equal (Current, Result) frozen standard_copy (other: SEQ [G]) -- Copy every field of other onto corresponding field -- of current object. -- (from ANY) require -- from ANY other_not_void: other /= Void type_identity: same_type (other) ensure -- from ANY is_standard_equal: standard_is_equal (other) frozen standard_twin: SEQ [G] -- New object field-by-field identical to other. -- Always uses default copying semantics. -- (from ANY) ensure -- from ANY standard_twin_not_void: Result /= Void equal: standard_equal (Result, Current) frozen twin: SEQ [G] -- New object equal to Current -- twin calls copy; to change copying/twinning semantics, redefine copy. -- (from ANY) ensure -- from ANY twin_not_void: Result /= Void is_equal: Result ~ Current feature -- Basic operations frozen default: detachable SEQ [G] -- Default value of object's type -- (from ANY) frozen default_pointer: POINTER -- Default value of type POINTER -- (Avoid the need to write p.default for -- some p of type POINTER.) -- (from ANY) ensure -- from ANY instance_free: class default_rescue -- Process exception for routines with no Rescue clause. -- (Default: do nothing.) -- (from ANY) frozen do_nothing -- Execute a null action. -- (from ANY) ensure -- from ANY instance_free: class feature -- 2-level copy twin2: like Current feature -- Auxiliary functions for contracts valid_position (pos: INTEGER_32): BOOLEAN -- Is 'pos' a valid position in current sequence ensure Result = (1 <= pos and pos <= # Current) feature -- Commands append (v: G) -- Add v to end. ensure Current ~ old Current.deep_twin.appended (v) concatenate (other: like Current) -- Append 'other' to the end of current sequence ensure Current ~ old Current.deep_twin.concatenated (other) insert (v: G; i: INTEGER_32) -- Insert 'v' as the i-th entry, if in index interval -- e.g., insert(1) on an empty sequence is forbidden. require valid_position (i) ensure Current ~ old Current.deep_twin.inserted (v, i) override (v: G; i: INTEGER_32) -- Replace i-th entry, if in index interval, by v. require valid_position (i) ensure Current ~ old Current.deep_twin.overriden (v, i) prepend (v: G) -- Add v to beginning. ensure Current ~ old Current.deep_twin.prepended (v) remove (i: INTEGER_32) -- Remove i-th entry, if in index interval require valid_position (i) ensure Current ~ old Current.deep_twin.removed (i) reverse -- Reverse the order of current sequence ensure Current ~ old Current.deep_twin.reversed subsequence (i, j: INTEGER_32) -- Cut down current seq so that segment i..j remains require valid_position (i) valid_position (j) ensure Current ~ old Current.deep_twin.subsequenced (i, j) feature -- Constructors make_empty -- create empty list ensure is_empty: is_empty make_from_array (a: ARRAY [G]) -- Create list from array a. ensure # Current = a.count across a.lower |..| a.upper as i all Current [i.item - a.lower + 1] ~ a [i.item] end feature -- Equality is_equal (other: like Current): BOOLEAN -- Is current sequence equal to other? require -- from ANY other_not_void: other /= Void ensure -- from ANY symmetric: Result implies other ~ Current consistent: standard_is_equal (other) implies Result ensure then Result = (as_function ~ other.as_function) feature -- Iteration new_cursor: ITERATION_CURSOR [G] -- A new cursor for iterating through current sequence ensure -- from ITERABLE result_attached: Result /= Void feature -- Output debug_output: STRING_8 -- Return string representation of current sequence for debugging ensure -- from DEBUG_OUTPUT result_not_void: Result /= Void Io: STD_FILES -- Handle to standard file setup -- (from ANY) ensure -- from ANY instance_free: class io_not_void: Result /= Void out: STRING_8 -- Return string representation of current sequence. ensure -- from ANY out_not_void: Result /= Void print (o: detachable ANY) -- Write terse external representation of o -- on standard output. -- (from ANY) ensure -- from ANY instance_free: class frozen tagged_out: STRING_8 -- New string containing terse printable representation -- of current object -- (from ANY) ensure -- from ANY tagged_out_not_void: Result /= Void feature -- Platform Operating_environment: OPERATING_ENVIRONMENT -- Objects available from the operating system -- (from ANY) ensure -- from ANY instance_free: class operating_environment_not_void: Result /= Void feature -- Quantification comprehension alias "|" (exp: PREDICATE [PAIR [INTEGER_32, G]]): like Current -- Form elements of current sequence that satisfy exp -- as a new sequence ensure current_set_unchanged: Current ~ old Current.deep_twin all_satisfying_items_exist: across Result as cur all Current.has (cur.item) end all_satisfying_exp: Result.hold_count (exp) = # Result consistent_satisfying_items: Current.hold_count (exp) = # Result hold_count (exp: PREDICATE [PAIR [INTEGER_32, G]]): INTEGER_32 -- How many items satisfying exp are in Current? ensure current_seq_unchanged: Current ~ old Current.deep_twin maximum_result: Result <= count feature -- Specification Queries appended alias "|->" (v: G): like Current -- Return a sequence representing current with 'v' added to end ensure current_seq_unchanged: Current ~ old Current.deep_twin count_incremented: # Result = # Current + 1 Result.front ~ Current Result.last ~ v concatenated alias "|++|" (other: like Current): like Current -- Return a sequence representing current with 'other' appended ensure current_seq_unchanged: Current ~ old Current.deep_twin count_incremented: # Result = # Current + # other across 1 |..| (# Current + # other) as pos all pos.item <= # Current implies Result [pos.item] ~ Current [pos.item] and pos.item > # Current implies Result [pos.item] ~ other [pos.item - # Current] end inserted (v: G; i: INTEGER_32): like Current -- Return a new sequence representing current with -- v inserted as the i-th entry, if in index interval require valid_position (i) ensure current_seq_unchanged: Current ~ old Current.deep_twin count_incremented: # Result = # Current + 1 Result ~ subsequenced (1, i - 1).appended (v) |++| subsequenced (i, count) overriden (v: G; i: INTEGER_32): like Current require valid_position (i) ensure current_seq_unchanged: Current ~ old Current.deep_twin count_incremented: # Current = # Result across 1 |..| count as pos all pos.item = i implies Result [pos.item] ~ v and pos.item /= i implies Result [pos.item] ~ Current [pos.item] end prepended alias "|<-" (v: G): like Current -- Return a sequence representing current with 'v' added to beginning ensure current_seq_unchanged: Current ~ old Current.deep_twin count_incremented: # Result = # Current + 1 Result.first ~ v Result.tail ~ Current removed (i: INTEGER_32): like Current -- Return a new sequence representing current with -- i-th entry, if in index interval, removed require valid_position (i) ensure current_seq_unchanged: Current ~ old Current.deep_twin count_decremented: # Result = # Current - 1 Result ~ subsequenced (1, i - 1) |++| subsequenced (i + 1, count) reversed: like Current -- Return an reversed version of current sequence ensure current_seq_unchanged: Current ~ old Current.deep_twin same_count: # Current = # Result reverse_property_1: Current ~ Result.reversed reverse_property_2: across 1 |..| count as i all Current [i.item] ~ Result [count - i.item + 1] end slice (a_start, a_end, a_step: INTEGER_32): like Current require lower <= a_start and a_start <= a_end and a_end <= upper a_step >= 0 subsequenced (i, j: INTEGER_32): like Current -- Segment of sequence i..j require valid_position (i) valid_position (j) ensure current_seq_unchanged: Current ~ old Current.deep_twin j >= i implies # Result = j - i + 1 j < i implies # Result = 0 across i |..| j as pos all Current [pos.item] ~ Result [pos.item - i + 1] end feature -- Status Queries count alias "#": INTEGER_32 -- Return the number of elements in current sequence ensure Result = as_array.count Result = # as_function first: G -- Return the 1st element in current sequence require not is_empty ensure Result ~ as_array [1] Result ~ as_function [1] front: like Current -- Return current sequence except the last element require not is_empty ensure case_of_empty_init: # Current = 1 implies Result.is_empty case_of_nonempty_init: # Current > 1 implies Result ~ subsequenced (1, count - 1) has (v: G): BOOLEAN -- Does 'v' exist in current sequence? ensure Result = across 1 |..| count as i some Current [i.item] ~ v end is_contiguous_subseq_of (other: like Current): BOOLEAN -- Is current a contiguous subsequence of 'other'? -- e.g. contiguous subsequences of <2, 3, 8, 5, 2> are: -- <>, <2, 3> <3, 8, 5> etc. ensure case_current_empty: is_empty implies Result case_other_empty: other.is_empty implies Result = is_empty case_both_non_empty: not (is_empty or other.is_empty) implies Result = (across 1 |..| # other as start_pos some across 1 |..| # other as end_pos some end_pos.item >= start_pos.item and Current ~ other.subsequenced (start_pos.item, end_pos.item) end end) is_empty: BOOLEAN -- Is the current sequence empty? ensure Result = (# Current = 0) Result = as_array.is_empty Result = as_function.is_empty is_subsequence_of alias "|<:" (other: like Current): BOOLEAN -- Is current a contiguous subsequence of 'other'? -- subsequences are not necessarily contiguous -- e.g. subsequences of <2, 3, 8, 5, 2> are: -- <>, <3, 5> <3, 5, 2> etc. item alias "[]" (i: INTEGER_32): G assign override -- Element at i-th position require valid_position (i) ensure Result ~ as_function [i] Result ~ as_array [i] last: G -- Return the last element in current sequence require not is_empty ensure Result ~ as_array [count] Result ~ as_function [count] lower: INTEGER_32 -- Starting position of current sequence ensure Result = 1 tail: like Current -- Return current sequence except the first element require not is_empty ensure case_of_empty_tail: # Current = 1 implies Result.is_empty case_of_nonempty_tail: # Current > 1 implies Result ~ subsequenced (2, count) upper: INTEGER_32 -- Ending position of current sequence ensure Result = # Current invariant value_semantics: imp.object_comparison lower = 1 imp.Lower = lower is_empty = (upper < lower) properties: not is_empty implies Current ~ tail.prepended (first) and Current ~ front.appended (last) -- from ANY reflexive_equality: standard_is_equal (Current) reflexive_conformance: conforms_to (Current) end -- class SEQ
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