NumberForm
 Usage
• NumberForm[expr, n]以n为精确度输出expr中的近似实数.
Notes
• NumberForm[expr,  n, f ]输出具有 n个数位的近似实数，其中小数点后占 f 位. • NumberForm 既适用于整数，也适用于近似实数. • 可以使用下列可选项:
| "\!\(\*StyleBox[\"\\\"DigitBlock\\\"\", \"MR\"]\) " | "\!\(\*StyleBox[\"\\\"Infinity\\\"\", \"MR\"]\) " | 空格之间的数位 | | "\!\(\*StyleBox[\"\\\"ExponentFunction\\\"\", \"MR\"]\) " | "\!\(\*StyleBox[\"\\\"Automatic\\\"\", \"MR\"]\) " | ""要应用到指数上的函数 | | "\!\(\*StyleBox[\"\\\"NumberFormat\\\"\", \"MR\"]\) " | "\!\(\*StyleBox[\"\\\"Automatic\\\"\", \"MR\"]\) " | 用来组合尾数，基底，指数的函数 | | "\!\(\*StyleBox[\"\\\"NumberPadding\\\"\", \"MR\"]\) " | "\!\(\*StyleBox[\"\\\"{\\\\\\\"\\\\\\\",\\\"\", \"MR\"]\) \!\(\*StyleBox[\"\\\"\\\\\\\"\\\\\\\"}\\\"\", \"MR\"]\) " | 用作左右填充字符的字符串 | | "\!\(\*StyleBox[\"\\\"NumberPoint\\\"\", \"MR\"]\) " | "\!\(\*StyleBox[\"\\\"\\\\\\\".\\\\\\\"\\\"\", \"MR\"]\) " | 小数点字符串 | | "\!\(\*StyleBox[\"\\\"NumberSeparator\\\"\", \"MR\"]\) " | "\!\(\*StyleBox[\"\\\"\\\\\\\",\\\\\\\"\\\"\", \"MR\"]\) " | "在数据块之间的空格处插入的字符串" | | "\!\(\*StyleBox[\"\\\"NumberSigns\\\"\", \"MR\"]\) " | "\!\(\*StyleBox[\"\\\"{\\\\\\\"-\\\\\\\",\\\"\", \"MR\"]\) \!\(\*StyleBox[\"\\\"\\\\\\\"+\\\\\\\"}\\\"\", \"MR\"]\) " | 用来标识负数和正书的字符串 | | "\!\(\*StyleBox[\"\\\"SignPadding\\\"\", \"MR\"]\) " | "\!\(\*StyleBox[\"\\\"False\\\"\", \"MR\"]\) " | 是否在标记后插入填充字符 |
• 除ExponentFunction外，所有可选项都同时适用于整数和近似实数. • 可以把NumberForm和BaseForm混合使用. • NumberForm相当于一个"包装"，它只影响输出，不影响计算.
 Further Examples
This breaks digits into blocks of length 3.
In[1]:=
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Out[1]//NumberForm=
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You can specify any string to use as a separator between blocks of digits.
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Out[2]//NumberForm=
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This gives an explicit plus sign for positive numbers, and uses | in place of a decimal point.
In[3]:=
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Out[3]//NumberForm=
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