(C++)cout格式化输出示例2009-09-10 09:04//<<a class="tags" href="/tags/IOS.html" title=ios>ios</a>tream>在使用setf等库函数时使用 //<iomanip>在使用流操纵算子时使用 //using namespace std; //以下所有的setf()都有对应的unsetf()用于取消设置 //所有的set<a class="tags" href="/tags/IOS.html" title=ios>ios</a>flags()可以用reset<a class="tags" href="/tags/IOS.html" title=ios>ios</a>flags()取消 //标志位fmtflags的命名空间可以使用<a class="tags" href="/tags/IOS.html" title=ios>ios</a>_base::或者<a class="tags" href="/tags/IOS.html" title=ios>ios</a>:: int laneri = 12345; double lanerd = 56789; //1、设置整数进制输出 //重载1：fmtflags <a class="tags" href="/tags/IOS.html" title=ios>ios</a>_base::setf(fmtflags _Mask); //重载2：fmtflags <a class="tags" href="/tags/IOS.html" title=ios>ios</a>_base::setf(fmtflags _Mask, fmtflags _Unset); //使用重载1的时候，一定要先取消当前基，之后才可以设置新的基 //使用重载2的时候，第二个参数设为当前的基，或者当不知道当前基时，设为<a class="tags" href="/tags/IOS.html" title=ios>ios</a>_base::basefield清除当前的所有可能的基 //可使用的标志：<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::dec, <a class="tags" href="/tags/IOS.html" title=ios>ios</a>::oct, <a class="tags" href="/tags/IOS.html" title=ios>ios</a>::<a class="tags" href="/tags/HEX.html" title=hex>hex</a>, <a class="tags" href="/tags/IOS.html" title=ios>ios</a>::basefield(= dec|oct|<a class="tags" href="/tags/HEX.html" title=hex>hex</a>) cout.unsetf(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::dec); //等价1 cout.setf(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::<a class="tags" href="/tags/HEX.html" title=hex>hex</a>); cout.setf(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::<a class="tags" href="/tags/HEX.html" title=hex>hex</a>, <a class="tags" href="/tags/IOS.html" title=ios>ios</a>_base::basefield); //等价2 cout<<laneri<<endl; cout<<set<a class="tags" href="/tags/IOS.html" title=ios>ios</a>flags(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::<a class="tags" href="/tags/HEX.html" title=hex>hex</a>)<<laneri<<endl; //等价3 cout<<std::<a class="tags" href="/tags/HEX.html" title=hex>hex</a><<laneri<<endl; //等价4 //使用输入输出操纵符也能有等价效果（命名空间使用std::，否则会有多余的字符），注意这种方法其实不止对本句生效 //2、 显示进制前导字符（0、0x） cout.setf(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::showbase); cout<<set<a class="tags" href="/tags/IOS.html" title=ios>ios</a>flags(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::showbase)<<laneri<<endl; cout<<std::showbase<<laneri<<endl; //3、使用科学记数法 //只对数据类型为小数的变量有效（或者字面值是小数） //对precision有影响（详见precision的说明） //对<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::fixed有影响（详见fixed的说明），但不会被fixed影响 cout.setf(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::scientific); cout<<lanerd<<endl; cout<<set<a class="tags" href="/tags/IOS.html" title=ios>ios</a>flags(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::scientific)<<lanerd<<endl; cout<<std::scientific<<lanerd<<endl; //4、设置小数的浮点/定点显示方式 //主要依靠precision体现（详见precision的说明） //当设置了<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::scientific标志时，<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::fixed会受到影响，std::fixed不会 cout.setf(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::fixed); cout<<lanerd<<endl; cout<<set<a class="tags" href="/tags/IOS.html" title=ios>ios</a>flags(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::fixed)<<lanerd<<endl; cout<<std::fixed<<lanerd<<endl; //5、设置小数数据类型的显示精度，受到scientific和fixed的影响 //当设置(fixed | scientific)时，precision(n)表示小数点后固定显示n位小数 //当不设置(fixed & scientific)时，precision(n)表示固定显示n位数字 // 其中，当是整数且位数m小于n，而又没有设置showpoint的时候，只显示m位整数。例如：precision(3)，12->12 // 其中，当是整数且位数p大于n，无论设置showpoint与否，都四舍五入后使用科学计数法。例如：precision(3)，1234->1.23e+003 cout.precision(3); cout<<lanerd<<endl; cout<<setprecision(3)<<3.1415926<<endl; //6、强制浮点数类型变量的小数点显示 //如果是整数，大于precision宽度时使用科学计数法，小于precision则小数点后面补0，等于precision时显示小数点但无小数 //例：不设fixed，precision(6)： 1234567->1.23457E+006; 12345->12345.0; 123456->123456. //　　设fixed，precision(6)： 1234567->1234567.000000; 12345->12345.000000; 123456->123456.000000 cout.setf(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::showpoint); cout<<set<a class="tags" href="/tags/IOS.html" title=ios>ios</a>flags(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::showpoint)<<lanerd<<endl; cout<<std::showpoint<<lanerd<<endl; //7、设置屏幕上的最小显示宽度 //实际字符数大于等于这个数字，显示全部；小于这个数字，用fill()设置的字符来填充其他占位符 //注意：宽度设置只对下一个"<<"输出有效 //例如：cout<<setw(10)<<right<<"laner"<<"linke";只有"laner"是占10个字符，linke不是 cout.width(12); cout<<setw(12)<<3.14<<endl; //8、显示对齐方式，默认为左对齐 cout.setf(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::right); cout<<set<a class="tags" href="/tags/IOS.html" title=ios>ios</a>flags(<a class="tags" href="/tags/IOS.html" title=ios>ios</a>::right)<<laneri<<endl; cout<<std::right<<6.28<<endl; //9、设置不足显示宽度时的填充字符，默认为' ' cout.fill('*'); cout<<setfill('$')<<laneri<<endl; ===================================================================== //附：<a class="tags" href="/tags/IOS.html" title=ios>ios</a>_base::fmtflags /* *dec, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> or extract <a class="tags" href="/tags/INTEGER.html" title=integer>integer</a> values in decimal format. *<a class="tags" href="/tags/HEX.html" title=hex>hex</a>, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> or extract <a class="tags" href="/tags/INTEGER.html" title=integer>integer</a> values in <a class="tags" href="/tags/HEX.html" title=hex>hex</a>adecimal format. *oct, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> or extract <a class="tags" href="/tags/INTEGER.html" title=integer>integer</a> values in octal format. *showbase, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> a prefix that reveals the base of a generated <a class="tags" href="/tags/INTEGER.html" title=integer>integer</a> field. *internal, to pad to a field width as needed by <a class="tags" href="/tags/INSERT.html" title=insert>insert</a>ing fill characters at a point internal to a generated numeric field. (For information on setting the field width, see setw). *left, to pad to a field width as needed by <a class="tags" href="/tags/INSERT.html" title=insert>insert</a>ing fill characters at the end of a generated field (left justification). *right, to pad to a field width as needed by <a class="tags" href="/tags/INSERT.html" title=insert>insert</a>ing fill characters at the beginning of a generated field (right justification). *boolalpha, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> or extract objects of type bool as names (such as true and false) rather than as numeric values. *fixed, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> floating-point values in fixed-point format (with no exponent field). *scientific, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> floating-point values in scientific format (with an exponent field). *showpoint, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> a decimal point unconditionally in a generated floating-point field. *showpos, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> a plus sign in a nonnegative generated numeric field. *skipws, to skip leading white space before certain extractions. *unitbuf, to flush <a class="tags" href="/tags/OUTPUT.html" title=output>output</a> after <a class="tags" href="/tags/EACH.html" title=each>each</a> <a class="tags" href="/tags/INSERT.html" title=insert>insert</a>ion. *uppercase, to <a class="tags" href="/tags/INSERT.html" title=insert>insert</a> uppercase equivalents of lowercase letters in certain <a class="tags" href="/tags/INSERT.html" title=insert>insert</a>ions. -------------------------------- *adjustfield, a bitmask defined as internal | left | right *basefield, defined as dec | <a class="tags" href="/tags/HEX.html" title=hex>hex</a> | oct *floatfield, defined as fixed | scientific */