C语言 如何在不四舍五入的情况下将浮点值打印到小数点后两位
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how to print float value upto 2 decimal place without rounding off
提问by pankanaj
For example I want to print a value in c up to 2 decimal places, without rounding it off.
例如，我想将 c 中的值打印到小数点后 2 位，而不将其四舍五入。
like:
喜欢：
a = 91.827345;
printf("%.2f", a);
will print 91.83, but I want output to be 91.82only. How to do it?
将打印91.83，但我只想输出91.82。怎么做？
回答by Opsenas
i'd suggest shorter and faster approach:
我建议更短和更快的方法：
printf("%.2f", ((signed long)(fVal * 100) * 0.01f));
this way you won't overflow int, plus multiplication by 100 shouldn't influence the significand/mantissa itself, because the only thing that really is changing is exponent.
这样你就不会溢出 int，再加上乘以 100 不应该影响有效数/尾数本身，因为唯一真正改变的是指数。
回答by R.. GitHub STOP HELPING ICE
The only easy way to do this is to use snprintfto print to a buffer that's long enough to hold the entire, exact value, then truncate it as a string. Something like:
执行此操作的唯一简单方法是使用snprintf打印到足够长的缓冲区来保存整个精确值，然后将其截断为字符串。就像是：
char buf[2*(DBL_MANT_DIG + DBL_MAX_EXP)];
snprintf(buf, sizeof buf, "%.*f", (int)sizeof buf, x);
char *p = strchr(buf, '.'); // beware locale-specific radix char, though!
p[2+1] = 0;
puts(buf);
