Why is `const int& k = i; ++i; ` possible?












6















I am supposed to determine whether this function is syntactically correct:



int f3(int i, int j) { const int& k=i; ++i; return k; }



I have tested it out and it compiles with my main function.



I do not understand why this is so.



Surely by calling the function f3 I create copies of the variables iand j in a new memory space and setting const int& k=i I am setting the memory space of the newly created k to the exact the same space of the memory space of the copied i, therefore any change, i.e. the increment ++iwill result in ++k which is not possible given that it was set const



Any help is greatly appreciated






c++ syntax reference const







share|improve this question



























    6















    I am supposed to determine whether this function is syntactically correct:



    int f3(int i, int j) { const int& k=i; ++i; return k; }



    I have tested it out and it compiles with my main function.



    I do not understand why this is so.



    Surely by calling the function f3 I create copies of the variables iand j in a new memory space and setting const int& k=i I am setting the memory space of the newly created k to the exact the same space of the memory space of the copied i, therefore any change, i.e. the increment ++iwill result in ++k which is not possible given that it was set const



    Any help is greatly appreciated






    c++ syntax reference const







    share|improve this question

























      6












      6








      6








      I am supposed to determine whether this function is syntactically correct:



      int f3(int i, int j) { const int& k=i; ++i; return k; }



      I have tested it out and it compiles with my main function.



      I do not understand why this is so.



      Surely by calling the function f3 I create copies of the variables iand j in a new memory space and setting const int& k=i I am setting the memory space of the newly created k to the exact the same space of the memory space of the copied i, therefore any change, i.e. the increment ++iwill result in ++k which is not possible given that it was set const



      Any help is greatly appreciated






      c++ syntax reference const







      share|improve this question














      I am supposed to determine whether this function is syntactically correct:



      int f3(int i, int j) { const int& k=i; ++i; return k; }



      I have tested it out and it compiles with my main function.



      I do not understand why this is so.



      Surely by calling the function f3 I create copies of the variables iand j in a new memory space and setting const int& k=i I am setting the memory space of the newly created k to the exact the same space of the memory space of the copied i, therefore any change, i.e. the increment ++iwill result in ++k which is not possible given that it was set const



      Any help is greatly appreciated






      c++ syntax reference const




      c++ syntax reference const






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 7 hours ago









      user9078057user9078057

      1118




      1118
























          1 Answer
          1






          active

          oldest

          votes


















          14















          the increment ++iwill result in ++k which is not possible given that it was set const




          That's a misunderstanding.



          You may not change the value of the object through k but it can still be changed through other means. In other words, ++k is not allowed but ++i is still allowed, which will indirectly modify the value of k.



          Here's a far-fetched analogy.



          You may look through the window of a store and see what's inside but you won't be able to change what's inside the store. However, an employee, who is inside the store, can change the contents of the store. You will see that change from
          outside. You have const access or view access to the store while the employee has non-const access or change access to the store.






          share|improve this answer





















          • 5





            Not so far-fetched. That's a good analogy.

            – user4581301
            6 hours ago











          • Note that this is so because i itself is not const. So we have a const reference a non-const object. Const objects are different.

            – David Schwartz
            6 hours ago











          Your Answer






          StackExchange.ifUsing("editor", function () {
          StackExchange.using("externalEditor", function () {
          StackExchange.using("snippets", function () {
          StackExchange.snippets.init();
          });
          });
          }, "code-snippets");

          StackExchange.ready(function() {
          var channelOptions = {
          tags: "".split(" "),
          id: "1"
          };
          initTagRenderer("".split(" "), "".split(" "), channelOptions);

          StackExchange.using("externalEditor", function() {
          // Have to fire editor after snippets, if snippets enabled
          if (StackExchange.settings.snippets.snippetsEnabled) {
          StackExchange.using("snippets", function() {
          createEditor();
          });
          }
          else {
          createEditor();
          }
          });

          function createEditor() {
          StackExchange.prepareEditor({
          heartbeatType: 'answer',
          autoActivateHeartbeat: false,
          convertImagesToLinks: true,
          noModals: true,
          showLowRepImageUploadWarning: true,
          reputationToPostImages: 10,
          bindNavPrevention: true,
          postfix: "",
          imageUploader: {
          brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
          contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
          allowUrls: true
          },
          onDemand: true,
          discardSelector: ".discard-answer"
          ,immediatelyShowMarkdownHelp:true
          });


          }
          });














          draft saved

          draft discarded


















          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55367062%2fwhy-is-const-int-k-i-i-possible%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown

























          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          14















          the increment ++iwill result in ++k which is not possible given that it was set const




          That's a misunderstanding.



          You may not change the value of the object through k but it can still be changed through other means. In other words, ++k is not allowed but ++i is still allowed, which will indirectly modify the value of k.



          Here's a far-fetched analogy.



          You may look through the window of a store and see what's inside but you won't be able to change what's inside the store. However, an employee, who is inside the store, can change the contents of the store. You will see that change from
          outside. You have const access or view access to the store while the employee has non-const access or change access to the store.






          share|improve this answer





















          • 5





            Not so far-fetched. That's a good analogy.

            – user4581301
            6 hours ago











          • Note that this is so because i itself is not const. So we have a const reference a non-const object. Const objects are different.

            – David Schwartz
            6 hours ago
















          14















          the increment ++iwill result in ++k which is not possible given that it was set const




          That's a misunderstanding.



          You may not change the value of the object through k but it can still be changed through other means. In other words, ++k is not allowed but ++i is still allowed, which will indirectly modify the value of k.



          Here's a far-fetched analogy.



          You may look through the window of a store and see what's inside but you won't be able to change what's inside the store. However, an employee, who is inside the store, can change the contents of the store. You will see that change from
          outside. You have const access or view access to the store while the employee has non-const access or change access to the store.






          share|improve this answer





















          • 5





            Not so far-fetched. That's a good analogy.

            – user4581301
            6 hours ago











          • Note that this is so because i itself is not const. So we have a const reference a non-const object. Const objects are different.

            – David Schwartz
            6 hours ago














          14












          14








          14








          the increment ++iwill result in ++k which is not possible given that it was set const




          That's a misunderstanding.



          You may not change the value of the object through k but it can still be changed through other means. In other words, ++k is not allowed but ++i is still allowed, which will indirectly modify the value of k.



          Here's a far-fetched analogy.



          You may look through the window of a store and see what's inside but you won't be able to change what's inside the store. However, an employee, who is inside the store, can change the contents of the store. You will see that change from
          outside. You have const access or view access to the store while the employee has non-const access or change access to the store.






          share|improve this answer
















          the increment ++iwill result in ++k which is not possible given that it was set const




          That's a misunderstanding.



          You may not change the value of the object through k but it can still be changed through other means. In other words, ++k is not allowed but ++i is still allowed, which will indirectly modify the value of k.



          Here's a far-fetched analogy.



          You may look through the window of a store and see what's inside but you won't be able to change what's inside the store. However, an employee, who is inside the store, can change the contents of the store. You will see that change from
          outside. You have const access or view access to the store while the employee has non-const access or change access to the store.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 7 hours ago

























          answered 7 hours ago









          R SahuR Sahu

          169k1294193




          169k1294193








          • 5





            Not so far-fetched. That's a good analogy.

            – user4581301
            6 hours ago











          • Note that this is so because i itself is not const. So we have a const reference a non-const object. Const objects are different.

            – David Schwartz
            6 hours ago














          • 5





            Not so far-fetched. That's a good analogy.

            – user4581301
            6 hours ago











          • Note that this is so because i itself is not const. So we have a const reference a non-const object. Const objects are different.

            – David Schwartz
            6 hours ago








          5




          5





          Not so far-fetched. That's a good analogy.

          – user4581301
          6 hours ago





          Not so far-fetched. That's a good analogy.

          – user4581301
          6 hours ago













          Note that this is so because i itself is not const. So we have a const reference a non-const object. Const objects are different.

          – David Schwartz
          6 hours ago





          Note that this is so because i itself is not const. So we have a const reference a non-const object. Const objects are different.

          – David Schwartz
          6 hours ago




















          draft saved

          draft discarded




















































          Thanks for contributing an answer to Stack Overflow!


          • Please be sure to answer the question. Provide details and share your research!

          But avoid …



          • Asking for help, clarification, or responding to other answers.

          • Making statements based on opinion; back them up with references or personal experience.


          To learn more, see our tips on writing great answers.




          draft saved


          draft discarded














          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55367062%2fwhy-is-const-int-k-i-i-possible%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown





















































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown

































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown







          -

          Popular posts from this blog

          SQL Server 17 - Attemping to backup to remote NAS but Access is denied

          Image
          .everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty{ margin-bottom:0; } 0 I was attemping to use Ola Hallengrens scripts to backup to a remote NAS, but it was failing and not giving any direct errors, so I tried doing it manually using Server Management Studio and got the following error: TITLE: Microsoft SQL Server Management Studio Failed to retrieve data for this request. (Microsoft.SqlServer.Management.Sdk.Sfc) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft%20SQL%20Server&LinkId=20476 ADDITIONAL INFORMATION: An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo) The operating system returned the error '0x80070005(Access is denied.)&#
          Read more

          Always On Availability groups resolving state after failover - Remote harden of transaction...

          Image
          0 My explanation will be opinion based as it is based on my findings. If more information is needed, I am always happy to add it. The setup We have 4 SQL Server 2016 Instances, and all 4 underlying servers are in a WSFC (In my eyes a strange setup since Always On AG's are 2 by 2. But that is a different question.) 4 nodes + Fileshare witness Version: 13.0.5026.0 (all nodes) The instances that are having the failover issues are instances 1 & 2. They have 3 AG's between them. AG1 is primary on instance 1 and is having the issue. AG2 and AG3 are primary on instance 2. Instances 3 and 4 have their own separate AG's (2). AG1's settings The week before Last week, after checking for long running queries (none) and the synchronization state (green accross the board) we initiated a
          Read more

          Restoring from pg_dump with foreign key constraints

          Image
          5 2 In restoring a database from a pg_dump , a number of errors are being generated and the whole table is subsequently being ignored. An example: ERROR: insert or update on table "channelproducts" violates foreign key constraint "fk_rails_dfaae373a5" DETAIL: Key (channel_id)=(1) is not present in table "channels". Interestingly enough, I've noted that all these instances are popping up because of the sequence of loading. channels is after channelproducts both alphabetically and in the file and thus I can understand why postgres complains about having to create a child without a parent. caveat: the foreign key is being generated automatically by rails 4.2: I could remove the problem at the source but that still does not really solve the problem... version: PostgreSQL
          Read more