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Why do C and C++ allow the expression (int) + 4*5;



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20















(int) + 4*5;


Why is this possible? (tried with g++ and gcc.)






c++ c casting language-lawyer







share|improve this question









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Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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  • Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^

    – bruno
    9 hours ago








  • 3





    same as (int)-4*5

    – P__J__
    8 hours ago











  • Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/

    – jamesqf
    7 hours ago






  • 1





    @jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.

    – Ernest Bredar
    6 hours ago






  • 3





    There is a useful tool called cppinsights that helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)

    – Nikita Kniazev
    2 hours ago


















20















(int) + 4*5;


Why is this possible? (tried with g++ and gcc.)






c++ c casting language-lawyer







share|improve this question









New contributor




Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





















  • Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^

    – bruno
    9 hours ago








  • 3





    same as (int)-4*5

    – P__J__
    8 hours ago











  • Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/

    – jamesqf
    7 hours ago






  • 1





    @jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.

    – Ernest Bredar
    6 hours ago






  • 3





    There is a useful tool called cppinsights that helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)

    – Nikita Kniazev
    2 hours ago














20












20








20








(int) + 4*5;


Why is this possible? (tried with g++ and gcc.)






c++ c casting language-lawyer







share|improve this question









New contributor




Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct. 












(int) + 4*5;


Why is this possible? (tried with g++ and gcc.)






c++ c casting language-lawyer




c++ c casting language-lawyer






share|improve this question









New contributor




Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|improve this question









New contributor




Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|improve this question




share|improve this question








edited 7 mins ago









Dai

74.6k15120209




74.6k15120209






New contributor




Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









asked 9 hours ago









Ernest BredarErnest Bredar

1155




1155




New contributor




Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





New contributor





Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.













  • Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^

    – bruno
    9 hours ago








  • 3





    same as (int)-4*5

    – P__J__
    8 hours ago











  • Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/

    – jamesqf
    7 hours ago






  • 1





    @jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.

    – Ernest Bredar
    6 hours ago






  • 3





    There is a useful tool called cppinsights that helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)

    – Nikita Kniazev
    2 hours ago



















  • Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^

    – bruno
    9 hours ago








  • 3





    same as (int)-4*5

    – P__J__
    8 hours ago











  • Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/

    – jamesqf
    7 hours ago






  • 1





    @jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.

    – Ernest Bredar
    6 hours ago






  • 3





    There is a useful tool called cppinsights that helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)

    – Nikita Kniazev
    2 hours ago

















Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^

– bruno
9 hours ago







Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^

– bruno
9 hours ago






3




3





same as (int)-4*5

– P__J__
8 hours ago





same as (int)-4*5

– P__J__
8 hours ago













Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/

– jamesqf
7 hours ago





Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/

– jamesqf
7 hours ago




1




1





@jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.

– Ernest Bredar
6 hours ago





@jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.

– Ernest Bredar
6 hours ago




3




3





There is a useful tool called cppinsights that helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)

– Nikita Kniazev
2 hours ago





There is a useful tool called cppinsights that helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)

– Nikita Kniazev
2 hours ago












2 Answers
2






active

oldest

votes


















34














The + here is unary + operator, not the binary addition operator. There's no addition happening here.



Also, the syntax (int) is used for typecasting.



You can re-read that statement as



(int) (+ 4) * 5;


which is parsed as



((int) (+ 4)) * (5);


which says,




  • Make the operand +4

  • typecasted to an int

  • multiply with operand 5


This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.



In your case, the unary + and the cast to int - both are redundant.






share|improve this answer

































    22














    This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.






    share|improve this answer
























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      2 Answers
      2






      active

      oldest

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      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      34














      The + here is unary + operator, not the binary addition operator. There's no addition happening here.



      Also, the syntax (int) is used for typecasting.



      You can re-read that statement as



      (int) (+ 4) * 5;


      which is parsed as



      ((int) (+ 4)) * (5);


      which says,




      • Make the operand +4

      • typecasted to an int

      • multiply with operand 5


      This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.



      In your case, the unary + and the cast to int - both are redundant.






      share|improve this answer






























        34














        The + here is unary + operator, not the binary addition operator. There's no addition happening here.



        Also, the syntax (int) is used for typecasting.



        You can re-read that statement as



        (int) (+ 4) * 5;


        which is parsed as



        ((int) (+ 4)) * (5);


        which says,




        • Make the operand +4

        • typecasted to an int

        • multiply with operand 5


        This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.



        In your case, the unary + and the cast to int - both are redundant.






        share|improve this answer




























          34












          34








          34







          The + here is unary + operator, not the binary addition operator. There's no addition happening here.



          Also, the syntax (int) is used for typecasting.



          You can re-read that statement as



          (int) (+ 4) * 5;


          which is parsed as



          ((int) (+ 4)) * (5);


          which says,




          • Make the operand +4

          • typecasted to an int

          • multiply with operand 5


          This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.



          In your case, the unary + and the cast to int - both are redundant.






          share|improve this answer















          The + here is unary + operator, not the binary addition operator. There's no addition happening here.



          Also, the syntax (int) is used for typecasting.



          You can re-read that statement as



          (int) (+ 4) * 5;


          which is parsed as



          ((int) (+ 4)) * (5);


          which says,




          • Make the operand +4

          • typecasted to an int

          • multiply with operand 5


          This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.



          In your case, the unary + and the cast to int - both are redundant.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 5 hours ago









          Dancrumb

          18.2k448103




          18.2k448103










          answered 9 hours ago









          Sourav GhoshSourav Ghosh

          112k15136194




          112k15136194

























              22














              This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.






              share|improve this answer




























                22














                This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.






                share|improve this answer


























                  22












                  22








                  22







                  This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.






                  share|improve this answer













                  This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered 9 hours ago









                  Igor TandetnikIgor Tandetnik

                  33.4k33559




                  33.4k33559






















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