>>300 こんな感じです。環境はlinuxです。(version 4.2.1) $ cat test.cpp int main(void) { int res = 0; int a = 0; res >?= a; return 0; } $ g++ test.cpp test.cpp: In function 'int main()': test.cpp:5: error: expected primary-expression before '?' token test.cpp:5: error: expected primary-expression before '=' token test.cpp:5: error: expected `:' before ';' token test.cpp:5: error: expected primary-expression before ';' token