foo.cc: In function 'int main()':
foo.cc:36:22: error: 'setprecison' was not declared in this scope
   36 |         cout<<fixed<<setprecison(6)<<val()<<endl;
      |                      ^~~~~~~~~~~
foo.cc: In function 'double Cal(double, char, double)':
foo.cc:12:1: warning: control reaches end of non-void function [-Wreturn-type]
   12 | }
      | ^

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