C initial value of reference to non-const must be an lvalue

Question

I m trying to send value into function using reference pointer but it gave me a completely non-obvious error to me   include  stdafx h   include  lt iostream gt   using namespace std   void test float   amp x         x   1000     int main        float nKByte   100 0      test  amp nKByte       cout  lt  lt  nKByte  lt  lt    megabytes   lt  lt  endl      cin get        Error   initial value of reference to non-const must be an lvalue  I have no idea what I must do to repair above code  can someone give me some ideas on how to fix that code  thanks

User · Answer

When you call test with  amp nKByte  the address-of operator creates a temporary value  and you can t normally have references to temporary values because they are  well  temporary   Either do not use a reference for the argument  or better yet don t use a pointer

User · Answer

When you pass a pointer by a non-const reference  you are telling the compiler that you are going to modify that pointer s value  Your code does not do that  but the compiler thinks that it does  or plans to do it in the future   To fix this error  either declare x constant     This tells the compiler that you are not planning to modify the pointer    passed by reference void test float   const  amp x        x   1000      or make a variable to which you assign a pointer to nKByte before calling test   float nKByte   100 0     If  test    decides to modify  x   the modification will be reflected in nKBytePtr float  nKBytePtr    amp nKByte  test nKBytePtr

User · Answer

The  amp nKByte creates a temporary value  which cannot be bound to a reference to non-const   You could change void test float   amp x  to void test float   const  amp x  or you could just drop the pointer altogether and use void test float  amp x           test nKByte

[c++] C++ initial value of reference to non-const must be an lvalue

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