规则，可以使用codice_1:<ref name="ISOs6.5/7"> ISO/IEC 9899:1999 s6.5/7</ref>bool is_negative(float x) {GCC编译器支持这样的语言扩展。其他的类型双关，见数组步长。
Pascal.A variant record permits treating a data type as multiple kinds of data depending on which variant is be