How to sort with a lambda

Question

sort mMyClassVector begin    mMyClassVector end            const MyClass  amp  a  const MyClass  amp  b         return a mProperty  gt  b mProperty         I d like to use a lambda function to sort custom classes in place of binding an instance method  However  the code above yields the error      error C2564   const char      a function-style conversion to a built-in type can only take one argument   It works fine with boost  bind  amp MyApp  myMethod  this   1   2

User · Answer

Got it   sort mMyClassVector begin    mMyClassVector end            const MyClass  amp  a  const MyClass  amp  b  - gt  bool        return a mProperty  gt  b mProperty         I assumed it d figure out that the   operator returned a bool  per documentation    But apparently it is not so

User · Answer

To much code  you can use it like this   include lt array gt   include lt functional gt   int main         std  array lt int  10 gt  vec     1 2 3 4 5 6 7 8 9         std  sort std  begin vec                  std  end vec                     int a  int b   return a  gt  b           for  auto item   vec        std  cout  lt  lt  item  lt  lt   quot   quot        return 0     Replace  quot vec quot  with your class and that s it

User · Answer

Can the problem be with the  a mProperty   b mProperty  line   I ve gotten the following code to work    include  lt algorithm gt   include  lt vector gt   include  lt iterator gt   include  lt iostream gt   include  lt sstream gt   struct Foo       Foo      i 0           int  i       friend std  ostream amp  operator lt  lt  std  ostream amp  os  const Foo amp  f                os  lt  lt  f  i          return os             typedef std  vector lt Foo gt  VectorT   std  string toString const VectorT amp  v        std  stringstream ss      std  copy v begin    v end    std  ostream iterator lt Foo gt  ss              return ss str        int main          VectorT v 10       std  for each v begin    v end                   Foo amp  f                                f  i   rand     100                       std  cout  lt  lt   before sort     lt  lt  toString v   lt  lt    n        sort v begin    v end                   const Foo amp  a  const Foo amp  b                                return a  i  gt  b  i                       std  cout  lt  lt   after sort      lt  lt  toString v   lt  lt    n       return 1       The output is   before sort  83  86  77  15  93  35  86  92  49  21  after sort   93  92  86  86  83  77  49  35  21  15

[c++] How to sort with a lambda?

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