晋太元中，武陵人捕鱼为业。缘溪行，忘路之远近。忽逢桃花林，夹岸数百步，中无杂树，芳草鲜美，落英缤纷。渔人甚异之，复前行，欲穷其林。 　　林尽水源，便得一山，山有小口，仿佛若有光。便舍船，从口入。初极狭，才通人。复行数十步，豁然开朗。土地平旷，屋舍俨然，有良田、美池、桑竹之属。阡陌交通，鸡犬相闻。其中往来种作，男女衣着，悉如外人。黄发垂髫，并怡然自乐。 　　见渔人，乃大惊，问所从来。具答之。便要还家，设酒杀鸡作食。村中闻有此人，咸来问讯。自云先世避秦时乱，率妻子邑人来此绝境，不复出焉，遂与外人间隔。问今是何世，乃不知有汉，无论魏晋。此人一一为具言所闻，皆叹惋。余人各复延至其家，皆出酒食。停数日，辞去。此中人语云：“不足为外人道也。”(间隔 一作：隔绝) 　　既出，得其船，便扶向路，处处志之。及郡下，诣太守，说如此。太守即遣人随其往，寻向所志，遂迷，不复得路。 　　南阳刘子骥，高尚士也，闻之，欣然规往。未果，寻病终。后遂无问津者。 .
Prv8 Shell
Server : Apache
System : Linux srv.rainic.com 4.18.0-553.47.1.el8_10.x86_64 #1 SMP Wed Apr 2 05:45:37 EDT 2025 x86_64
User : rainic ( 1014)
PHP Version : 7.4.33
Disable Function : exec,passthru,shell_exec,system
Directory :  /usr/share/doc/bc/

Upload File :
current_dir [ Writeable ] document_root [ Writeable ]

 

Current File : //usr/share/doc/bc/FAQ
Because of frequent questions ....... here is the BC FAQ


1) Why does BC have its own arbitrary precision number routines 
   (found in lib/number.c) rather than using GMP?

GMP has "integers" (no digits after a decimal), "rational numbers"
(stored as 2 integers) and "floats".  None of these will correctly
represent a POSIX BC number.  Floats are the closest, but will not
behave correctly for many computations.  For example, BC numbers have
a "scale" that represent the number of digits to represent after the
decimal point.  The multiplying two of these numbers requires one to
calculate an exact number of digits after the decimal point regardless
of the number of digits in the integer part.  GMP floats have a
"fixed, but arbitrary" mantissa and so multiplying two floats will end
up dropping digits BC must calculate.

2) The code "ibase=16; obase=10; FF" outputs FF, not 255.  Isn't this
   a bug?

No.  ibase changed the input base at that point.  The 10 is then in
base 16 and thus is the value 16.  Therefore, both ibase and obase
are 16 (decimal).  And FF (base 16) on input is printed as FF (base 16)
on output.  So how can one get 255?  First, single digit numbers are
not converted using ibase.  So A is always 10 (decimal).  The following
code will always work.  "ibase=F+1; obase=A; FF" and that always prints
255.

3) Why is the scale variable ignored on multiply?

That is the way POSIX specifics multiply.  Reread the documentation for
the multiply operation and see that multiply uses the scales of the
numbers multiplied to determine the scale of the result.

4) bc's mod command is not working when I run with "bc -l".

bc's mod (%) command works like integer remainder when scale is 0.
The -l flag sets scale to 20 and that chanes how a % b is computed.
Read the man page for exact details.

haha - 2025