| Andes Workshop http://forum.andestech.com/ |
|
| 沒定義type的浮點數用double來處理 http://forum.andestech.com/viewtopic.php?f=25&t=642 |
Page 1 of 1 |
| Author: | cindy [ Fri Nov 23, 2012 5:17 pm ] |
| Post subject: | 沒定義type的浮點數用double來處理 |
下面有一個例子 1) 在 mainflow.c line #30, 有一段 float 的運算 abc=((uint32)(abb-aaa)*ba); 2) 在algo.c line #52 也有一段 float 的運算 bb=cc*0.2; 他們發現加入 1) 的 float 運算會增加一些 code size. 然後又加入 2) 的浮點運算又增加了 code size. ------------------------------ 解答 According to C99 6.4.4.2 point 4: "An unsuffixed floating constant has type double. If suffixed...." (C99 is C programming languague standard which is adopted by most C compiler) So the statement "bb=cc*0.2; " will use double-precision operation. If you would like to have floating constant with 'float' type, you should do explicitly casting or suffix it with the letter 'f'. bb = cc * (float)0.2; bb = cc * 0.2f; |
|
| Page 1 of 1 | All times are UTC + 8 hours [ DST ] |
| Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/ |
|