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





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(int) + 4*5;


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






c++ c casting language-lawyer







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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








  • 4





    same as (int)-4*5

    – P__J__
    8 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
    7 hours ago






  • 6





    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
    3 hours ago






  • 1





    This statement is equivalent to +(int)+ 4*5; and -(int)- 4*5; and -+-+-(int)-+-+- 4*5; and less poetically ;

    – chqrlie
    6 mins ago


















19















(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








  • 4





    same as (int)-4*5

    – P__J__
    8 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
    7 hours ago






  • 6





    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
    3 hours ago






  • 1





    This statement is equivalent to +(int)+ 4*5; and -(int)- 4*5; and -+-+-(int)-+-+- 4*5; and less poetically ;

    – chqrlie
    6 mins ago














19












19








19








(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 45 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.
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asked 9 hours ago









Ernest BredarErnest Bredar

1135




1135




New contributor




Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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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








  • 4





    same as (int)-4*5

    – P__J__
    8 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
    7 hours ago






  • 6





    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
    3 hours ago






  • 1





    This statement is equivalent to +(int)+ 4*5; and -(int)- 4*5; and -+-+-(int)-+-+- 4*5; and less poetically ;

    – chqrlie
    6 mins 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








  • 4





    same as (int)-4*5

    – P__J__
    8 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
    7 hours ago






  • 6





    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
    3 hours ago






  • 1





    This statement is equivalent to +(int)+ 4*5; and -(int)- 4*5; and -+-+-(int)-+-+- 4*5; and less poetically ;

    – chqrlie
    6 mins 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






4




4





same as (int)-4*5

– P__J__
8 hours ago





same as (int)-4*5

– P__J__
8 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
7 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
7 hours ago




6




6





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
3 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
3 hours ago




1




1





This statement is equivalent to +(int)+ 4*5; and -(int)- 4*5; and -+-+-(int)-+-+- 4*5; and less poetically ;

– chqrlie
6 mins ago





This statement is equivalent to +(int)+ 4*5; and -(int)- 4*5; and -+-+-(int)-+-+- 4*5; and less poetically ;

– chqrlie
6 mins ago












2 Answers
2






active

oldest

votes


















35














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


























  • "Casting", not "typecasting". Typecasting is something that happens to actors.

    – Keith Thompson
    36 mins ago











  • (+ 4) is not make the operand +4, it means apply the unary + to operand 4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For example char c = 0; sizeof +c == sizeof c is probably false and sizeof +"a" is probably not 2.

    – chqrlie
    11 mins ago



















23














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

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    35














    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


























    • "Casting", not "typecasting". Typecasting is something that happens to actors.

      – Keith Thompson
      36 mins ago











    • (+ 4) is not make the operand +4, it means apply the unary + to operand 4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For example char c = 0; sizeof +c == sizeof c is probably false and sizeof +"a" is probably not 2.

      – chqrlie
      11 mins ago
















    35














    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


























    • "Casting", not "typecasting". Typecasting is something that happens to actors.

      – Keith Thompson
      36 mins ago











    • (+ 4) is not make the operand +4, it means apply the unary + to operand 4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For example char c = 0; sizeof +c == sizeof c is probably false and sizeof +"a" is probably not 2.

      – chqrlie
      11 mins ago














    35












    35








    35







    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 6 hours ago









    Dancrumb

    18.2k448103




    18.2k448103










    answered 9 hours ago









    Sourav GhoshSourav Ghosh

    112k15136194




    112k15136194













    • "Casting", not "typecasting". Typecasting is something that happens to actors.

      – Keith Thompson
      36 mins ago











    • (+ 4) is not make the operand +4, it means apply the unary + to operand 4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For example char c = 0; sizeof +c == sizeof c is probably false and sizeof +"a" is probably not 2.

      – chqrlie
      11 mins ago



















    • "Casting", not "typecasting". Typecasting is something that happens to actors.

      – Keith Thompson
      36 mins ago











    • (+ 4) is not make the operand +4, it means apply the unary + to operand 4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For example char c = 0; sizeof +c == sizeof c is probably false and sizeof +"a" is probably not 2.

      – chqrlie
      11 mins ago

















    "Casting", not "typecasting". Typecasting is something that happens to actors.

    – Keith Thompson
    36 mins ago





    "Casting", not "typecasting". Typecasting is something that happens to actors.

    – Keith Thompson
    36 mins ago













    (+ 4) is not make the operand +4, it means apply the unary + to operand 4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For example char c = 0; sizeof +c == sizeof c is probably false and sizeof +"a" is probably not 2.

    – chqrlie
    11 mins ago





    (+ 4) is not make the operand +4, it means apply the unary + to operand 4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For example char c = 0; sizeof +c == sizeof c is probably false and sizeof +"a" is probably not 2.

    – chqrlie
    11 mins ago













    23














    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




























      23














      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


























        23












        23








        23







        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




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