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 SEQ [G -> attached ANY] inherit ITERABLE [G] redefine is_equal, out end DEBUG_OUTPUT undefine is_equal, out end create make_empty, make_from_array convert make_from_array ({ARRAY [G]}), as_array: {ARRAY [G]} feature -- 2-level copy twin2: like Current do Result := Current.twin Result.set_imp (Current.imp.twin) end feature -- Constructors make_empty -- create empty list do create imp.make (10) imp.compare_objects ensure is_empty: is_empty end make_from_array (a: ARRAY [G]) -- Create list from array a. do create imp.make_from_array (a) imp.compare_objects ensure # Current = a.count across a.lower |..| a.upper as i all Current [i.item - a.lower + 1] ~ a [i.item] end end feature -- Iteration new_cursor: ITERATION_CURSOR [G] -- A new cursor for iterating through current sequence do Result := imp.new_cursor end feature -- Status Queries count alias "#": INTEGER_32 -- Return the number of elements in current sequence do Result := imp.count ensure Result = as_array.count Result = # as_function end lower: INTEGER_32 -- Starting position of current sequence do Result := 1 ensure Result = 1 end upper: INTEGER_32 -- Ending position of current sequence do Result := count ensure Result = # Current end is_empty: BOOLEAN -- Is the current sequence empty? do Result := count = 0 ensure Result = (# Current = 0) Result = as_array.is_empty Result = as_function.is_empty end has (v: G): BOOLEAN -- Does 'v' exist in current sequence? do Result := imp.has (v) ensure Result = across 1 |..| count as i some Current [i.item] ~ v end end first: G -- Return the 1st element in current sequence require not is_empty do Result := imp [imp.Lower] ensure Result ~ as_array [1] Result ~ as_function [1] end front: like Current -- Return current sequence except the last element require not is_empty do if count > 1 then Result := subsequenced (1, count - 1) else create Result.make_empty end ensure case_of_empty_init: # Current = 1 implies Result.is_empty case_of_nonempty_init: # Current > 1 implies Result ~ subsequenced (1, count - 1) end last: G -- Return the last element in current sequence require not is_empty do Result := imp [imp.upper] ensure Result ~ as_array [count] Result ~ as_function [count] end tail: like Current -- Return current sequence except the first element require not is_empty do if count > 1 then Result := subsequenced (2, count) else create Result.make_empty end ensure case_of_empty_tail: # Current = 1 implies Result.is_empty case_of_nonempty_tail: # Current > 1 implies Result ~ subsequenced (2, count) end item alias "[]" (i: INTEGER_32): G assign override -- Element at i-th position require valid_position (i) do Result := imp.i_th (i) ensure Result ~ as_function [i] Result ~ as_array [i] end 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. local proj: SEQ [G] ran: SET [G] element: G do ran := Current.as_function.range create proj.make_empty across other as o loop element := o.item if ran.has (element) then proj.append (element) end end Result := is_augmented_subseq_of (augmented_with_collapsed_rep, proj.augmented_with_collapsed_rep) 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. do Result := is_augmented_subseq_of (augmented_without_collapsed_rep, other.augmented_without_collapsed_rep) 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) end feature -- Commands append (v: G) -- Add v to end. do imp.extend (v) ensure Current ~ old Current.deep_twin.appended (v) end prepend (v: G) -- Add v to beginning. do imp.put_front (v) ensure Current ~ old Current.deep_twin.prepended (v) end subsequence (i, j: INTEGER_32) -- Cut down current seq so that segment i..j remains require valid_position (i) valid_position (j) local pos: INTEGER_32 do if i <= j then from pos := 1 imp.start until imp.after loop if pos < i or pos > j then imp.remove else imp.forth end pos := pos + 1 end else make_empty end ensure Current ~ old Current.deep_twin.subsequenced (i, j) end concatenate (other: like Current) -- Append 'other' to the end of current sequence do across other as cur loop append (cur.item) end ensure Current ~ old Current.deep_twin.concatenated (other) end override (v: G; i: INTEGER_32) -- Replace i-th entry, if in index interval, by v. require valid_position (i) do imp.put_i_th (v, i) ensure Current ~ old Current.deep_twin.overriden (v, i) end 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) local j: INTEGER_32 done: BOOLEAN do from imp.start j := 1 until done loop if j = i then imp.put_left (v) done := True end imp.forth j := j + 1 end ensure Current ~ old Current.deep_twin.inserted (v, i) end remove (i: INTEGER_32) -- Remove i-th entry, if in index interval require valid_position (i) do imp.start if imp.count > 1 then imp.move (i - 1) end imp.remove ensure Current ~ old Current.deep_twin.removed (i) end reverse -- Reverse the order of current sequence local new_imp: like imp do create new_imp.make_filled (count) new_imp.compare_objects across 1 |..| count as i loop new_imp [count - i.item + 1] := Current [i.item] end set_imp (new_imp) ensure Current ~ old Current.deep_twin.reversed end feature -- Specification Queries appended alias "|->" (v: G): like Current -- Return a sequence representing current with 'v' added to end do Result := Current.deep_twin Result.append (v) ensure current_seq_unchanged: Current ~ old Current.deep_twin count_incremented: # Result = # Current + 1 Result.front ~ Current Result.last ~ v end prepended alias "|<-" (v: G): like Current -- Return a sequence representing current with 'v' added to beginning do Result := Current.deep_twin Result.prepend (v) ensure current_seq_unchanged: Current ~ old Current.deep_twin count_incremented: # Result = # Current + 1 Result.first ~ v Result.tail ~ Current end subsequenced (i, j: INTEGER_32): like Current -- Segment of sequence i..j require valid_position (i) valid_position (j) do Result := Current.deep_twin Result.subsequence (i, 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 end concatenated alias "|++|" (other: like Current): like Current -- Return a sequence representing current with 'other' appended do Result := Current.deep_twin Result.concatenate (other) 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 end overriden (v: G; i: INTEGER_32): like Current require valid_position (i) do Result := Current.deep_twin Result.override (v, 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 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) do Result := Current.deep_twin Result.insert (v, 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) end 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) do Result := Current.deep_twin Result.remove (i) ensure current_seq_unchanged: Current ~ old Current.deep_twin count_decremented: # Result = # Current - 1 Result ~ subsequenced (1, i - 1) |++| subsequenced (i + 1, count) end reversed: like Current -- Return an reversed version of current sequence do Result := Current.deep_twin Result.reverse 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 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 local i: INTEGER_32 do create Result.make_empty from i := a_start until i > a_end loop Result.append (item (i)) i := i + a_step end end feature -- Quantification hold_count (exp: PREDICATE [PAIR [INTEGER_32, G]]): INTEGER_32 -- How many items satisfying exp are in Current? local i: INTEGER_32 p: PAIR [INTEGER_32, G] do i := 1 across Current as c loop create p.make (i, c.item) if exp.item ([p]) then Result := Result + 1 end i := i + 1 end ensure current_seq_unchanged: Current ~ old Current.deep_twin maximum_result: Result <= count end comprehension alias "|" (exp: PREDICATE [PAIR [INTEGER_32, G]]): like Current -- Form elements of current sequence that satisfy exp -- as a new sequence local i: INTEGER_32 p: PAIR [INTEGER_32, G] do create Result.make_empty i := 1 across Current as c loop create p.make (i, c.item) if exp.item ([p]) then Result.append (c.item) end i := i + 1 end 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 end feature -- Equality is_equal (other: like Current): BOOLEAN -- Is current sequence equal to other? do Result := imp ~ other.imp ensure then Result = (as_function ~ other.as_function) end feature -- Output out: STRING_8 -- Return string representation of current sequence. local i: INTEGER_32 do create Result.make_empty Result.append ("< ") from i := 1 until i > count loop check attached {G} imp.i_th (i) as e then Result.append (e.out) end if i < count then Result.append (", ") end i := i + 1 end Result.append (" >") end debug_output: STRING_8 -- Return string representation of current sequence for debugging do Result := out end feature -- Conversion as_array: ARRAY [G] -- Return current sequence as an array do create Result.make_empty across Current as cur loop Result.force (cur.item, Result.upper + 1) end Result.compare_objects 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 end as_function: FUN [INTEGER_32, G] -- Return current sequence as a function -- with its domain being the set of positions local i: INTEGER_32 pair: PAIR [INTEGER_32, G] do create Result.make_empty i := 1 across Current as cur loop create pair.make (i, cur.item) Result.extend (pair) i := i + 1 end 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 end feature -- Auxiliary functions for contracts valid_position (pos: INTEGER_32): BOOLEAN -- Is 'pos' a valid position in current sequence do Result := 1 <= pos and then pos <= count ensure Result = (1 <= pos and pos <= # Current) end feature {SEQ} -- Auxiliary functions for checking subsequences is_augmented_subseq_of (s1, s2: SEQ [TUPLE [g: G; i: INTEGER_32]]): BOOLEAN -- Given that both 's1' and 's2' are augmented sequences, -- is 's1' a contiguous subsequence of 's2'? -- e.g., <<[a, 1], [b, 2]>> is a contiguous subsequence of -- <<[a, 3], [b, 3]>> local i: INTEGER_32 do if s1.is_empty then Result := True else from Result := False i := 1 until Result or else s2.count - i + 1 < s1.count loop if s1 [1].g ~ s2 [i].g then Result := across i |..| (i + s1.count - 1) as j all s1 [j.item - i.item + 1].g ~ s2 [j.item].g and then s1 [j.item - i.item + 1].i <= s2 [j.item].i end end i := i + 1 end end end augmented_with_collapsed_rep: SEQ [TUPLE [g: G; i: INTEGER_32]] -- e.g., <<a, b, b, c, d>> augmented to -- <<[a, 1], [b, 2], [c, 1], [d, 1]>> local i: INTEGER_32 element: G do create Result.make_empty from i := 1 imp.start until imp.after loop element := imp.item if i > 1 then if imp [i - 1] ~ element then Result [Result.count] := [Result.last.g, Result.last.i + 1] else Result.append ([element, 1]) end else Result.append ([element, 1]) end i := i + 1 imp.forth end end augmented_without_collapsed_rep: SEQ [TUPLE [G, INTEGER_32]] -- e.g., <<a, b, b, c, d>> augmented to -- <<[a, 1], [b, 1], [b, 1], [c, 1], [d, 1]>> do create Result.make_empty across Current as cur loop Result.append ([cur.item, 1]) end end feature {SEQ} -- Implementation imp: ARRAYED_LIST [G] set_imp (new_imp: like imp) do imp := new_imp ensure imp = new_imp end 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) end -- class SEQ
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