c++ - Why does the function always refer to one specific parameter? -


in following code:

int sum(int a=40, int b=20) {    int result;     result = + b;     return (result); }  int main () {      int = 100;     int b = 200;     int result;       result = sum(a, b);     cout << "total value :" << result << endl;       result = sum(a);     cout << "total value :" << result << endl;      return 0; }

this produces:

 total value : 300  total value : 120

why the:

sum(a)

add (int a) in 2nd block (int b) in 1st block?

im confused why (b) value in 1st block used in (sum(a)), (a) value in 1st block ignored.

int sum(int a=40, int b=20) {     ... }

declares parameters a 40 , b to 20, if not specified. compiler service, sum(a) becomes sum(a, 20) (b not specified). similar this, sum() becomes sum(40, 20). a , b in method sum default parameters.


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