foo.cc: In function 'int main()':
foo.cc:22:19: warning: statement has no effect [-Wunused-value]
   22 |       b[i - 1][j] == 'R';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:24:19: warning: statement has no effect [-Wunused-value]
   24 |       b[i + 1][j] == 'R';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:26:19: warning: statement has no effect [-Wunused-value]
   26 |       b[i][j - 1] == 'R';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:28:19: warning: statement has no effect [-Wunused-value]
   28 |       b[i][j + 1] == 'R';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:32:19: warning: statement has no effect [-Wunused-value]
   32 |       b[i - 1][j] == 'S';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:34:19: warning: statement has no effect [-Wunused-value]
   34 |       b[i + 1][j] == 'S';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:36:19: warning: statement has no effect [-Wunused-value]
   36 |       b[i][j - 1] == 'S';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:38:19: warning: statement has no effect [-Wunused-value]
   38 |       b[i][j + 1] == 'S';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:42:19: warning: statement has no effect [-Wunused-value]
   42 |       b[i - 1][j] == 'P';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:44:19: warning: statement has no effect [-Wunused-value]
   44 |       b[i + 1][j] == 'P';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:46:19: warning: statement has no effect [-Wunused-value]
   46 |       b[i][j - 1] == 'P';
      |       ~~~~~~~~~~~~^~~~~~
foo.cc:48:19: warning: statement has no effect [-Wunused-value]
   48 |       b[i][j + 1] == 'P';
      |       ~~~~~~~~~~~~^~~~~~

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