note description: "Keeper for non-void entity scopes that uses stacks to track voidness status." legal: "See notice at end of class." status: "See notice at end of class." date: "$Date$" revision: "$Revision$" deferred class AST_STACKED_SCOPE_KEEPER [G] inherit AST_SCOPE_KEEPER feature {NONE} -- Creation make (n: like count) -- Create storage to keep at least `n' variables. require non_negative_n: n >= 0 n_small_enough: n <= max_count do scope := new_scope (n) create {ARRAYED_STACK [like scope]} outer_scopes.make (1) create {ARRAYED_STACK [like scope]} inner_scopes.make (1) count := n ensure count_set: count = n end feature -- Status report: nesting nesting_level: INTEGER -- Current nesting level of a compound do Result := outer_scopes.count end feature {AST_CONTEXT} -- Status report is_sibling_dominating: BOOLEAN -- <Precursor> do if has_siblings then -- Compare siblings. Result := is_dominating end end feature {NONE} -- Status report is_dominating: BOOLEAN -- Does variable information of a sibling dominate the previous one? require is_nested: nesting_level > 0 has_siblings: has_siblings deferred end feature {AST_CONTEXT} -- Modification: nesting enter_realm -- Enter a new complex instruction -- with inner compound parts. do -- Record current scope information. outer_scopes.extend (scope) -- Start new scope from the state of an outer one. scope := duplicate (scope) -- Reserve stack for sibling information. inner_scopes.extend (({like scope}).default) ensure then not_has_siblings: not has_siblings not_is_sibling_dominating: not is_sibling_dominating end update_realm -- Update realm scope information -- from the current state. do outer_scopes.replace (duplicate (scope)) end save_sibling -- Save scope information of a sibling in a complex instrution and restart recording using the outer scope. -- For example, Then_part of Elseif condition. do if has_siblings then -- Merge sibling scope information. merge_siblings else -- Record new sibling scope information. inner_scopes.replace (duplicate (scope)) end -- Start new scope from the state of an outer one. scope := duplicate (outer_scopes.item) ensure then has_siblings: has_siblings end update_sibling -- Update scope information of a sibling in a complex instrution and reuse it for the current scope. -- For example, Loop body. do if has_siblings then -- Merge sibling scope information. merge_siblings else -- Record new sibling scope information. inner_scopes.replace (duplicate (scope)) end -- Start new scope from the state of an updated inner one. scope := duplicate (inner_scopes.item) ensure then has_siblings: has_siblings end feature {AST_CONTEXT, AST_VISITOR} -- Modification: nesting leave_realm -- Leave a complex instruction and -- promote scope information to the outer compound. do if has_siblings and then attached inner_scopes.item as i then -- Promote nested scope information to the outer level. scope := i end -- Remove inner scope information. inner_scopes.remove -- Remove outer scope information and use the latest one. outer_scopes.remove end leave_optional_realm -- Leave a complex instruction and -- discard its scope information. -- For example, Debug instruction. do -- Remove inner scope information. inner_scopes.remove -- Restore original scope information. scope := outer_scopes.item -- Remove outer scope information. outer_scopes.remove end feature {NONE} -- Modification: nesting merge_siblings -- Merge sibling scope information from `scope' -- into `inner_scopes.item'. require has_siblings: has_siblings deferred end feature {NONE} -- Status report has_siblings: BOOLEAN -- Are there any siblings in the current instruction? do Result := inner_scopes.item /= ({like scope}).default end feature {NONE} -- Storage scope: G -- Current void-safe status of a local -- with True indicating non-void value and -- False indicating possibly void value outer_scopes: STACK [like scope] -- Outer scopes inner_scopes: STACK [detachable like scope] -- Inner scopes feature {NONE} -- Initialization new_scope (n: like count): like scope -- New scope that can track attachment status of `n' variables. deferred ensure result_attached: Result /= Void result_not_default: Result /= ({like scope}).default end feature {NONE} -- Duplication duplicate (s: like scope): like scope -- A duplicate of a scope `s' require s_attached: s /= Void do Result := s.twin ensure result_attached: Result /= Void result_set: Result ~ s end invariant scope_attached: scope /= Void outer_scopes_attached: outer_scopes /= Void inner_scopes_attached: inner_scopes /= Void same_level: outer_scopes.count = inner_scopes.count note copyright: "Copyright (c) 1984-2017, Eiffel Software" license: "GPL version 2 (see http://www.eiffel.com/licensing/gpl.txt)" licensing_options: "http://www.eiffel.com/licensing" copying: "[ This file is part of Eiffel Software's Eiffel Development Environment. Eiffel Software's Eiffel Development Environment is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2 of the License (available at the URL listed under "license" above). Eiffel Software's Eiffel Development Environment is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Eiffel Software's Eiffel Development Environment; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA ]" source: "[ Eiffel Software 5949 Hollister Ave., Goleta, CA 93117 USA Telephone 805-685-1006, Fax 805-685-6869 Website http://www.eiffel.com Customer support http://support.eiffel.com ]" end