C + + Programming (4th edition) Reading notes _ basic knowledge

Assigning values to variables

The commonly used variable assignment is to use "=" to assign values.

1 int 2;

However, if you assign a floating-point number to I, it will result in a loss of precision, preferably in C + + using the initialization list of the way "{}" to assign a value to the variable, so as to ensure that some types of information loss may cause the conversion of the type

1 #include <iostream>2usingnamespace  std; 3 4 int Main () {5     int I {2.3}; 6     return 0 ; 7 }

For example, the compiler will make an error.

<source>: in function ' int main () ': 5: <source>:5:12:error:narrowing conversion of ' 2.2999999999999998e+0 ' F Rom ' double ' to ' int. ' inside {} [-wnarrowing]int I {2.3};^compiler exited with result code 1 AutoLearn how to use auto with a for loop

1#include <iostream>2 using namespacestd;3 4 intMain () {5     intV[] = {0,1,2,3,4};6 7      for(Auto x:v) {8cout << x <<"\ t";9     }Tencout <<Endl; One      A      for(Auto i =0; I <sizeof(v)/sizeof(int); ++i) { -cout << V[i] <<"\ t";  -     } thecout <<Endl; -      -      for(Auto x: {0,1,2,3,4}) { -cout << x <<"\ t"; +     } -cout <<Endl; +      A      for(Auto x:v) { atX + =1; -     } -      for(Auto x:v) { -cout << x <<"\ t"; -     } -cout <<Endl; in      -     /*for cases without references, it can be understood that each element of V is put into X from beginning to end and printed*/ to      for(Auto &x:v) { +X + =1; -     } the      for(Auto x:v) { *cout << x <<"\ t"; $     }Panax Notoginsengcout <<Endl; -      the     return 0; +}

C + + Programming (4th edition) Reading notes _ basic knowledge