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Bug fix from Javier Goizueta.

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ROUND_MODE & round changed(source & docs).


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@4187 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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shigek 2003-07-28 02:56:43 +00:00
parent b388591ab7
commit 4cbf09d1fe
4 changed files with 86 additions and 71 deletions
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ext/bigdecimal/bigdecimal_en.html
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@ -156,18 +156,22 @@ Suppose the return value of the mode method is f,then
<B>[ROUND error control]</B><P>
Rounding operation can be controlled as:
<BLOCKQUOTE>
f = BigDecimal::mode(BigDecimal::COMP_MODE,flag)
f = BigDecimal::mode(BigDecimal::ROUND_MODE,flag)
</BLOCKQUOTE>
where flag must be one of:
<TABLE>
<TR><TD>COMP_MODE_TRUNCATE</TD><TD>truncate</TD></TR>
<TR><TD>COMP_MODE_ROUND</TD><TD>round,default</TD></TR>
<TR><TD>COMP_MODE_CEIL</TD><TD>ceil</TD></TR>
<TR><TD>COMP_MODE_FLOOR</TD><TD>floor</TD></TR>
<TR><TD>COMP_MODE_EVEN</TD><TD>Banker's rounding</TD></TR>
<TR><TD>ROUND_UP</TD><TD>round away from zero.</TD></TR>
<TR><TD>ROUND_DOWN</TD><TD>round towards zero(truncate).</TD></TR>
<TR><TD>ROUND_HALF_UP</TD><TD>round up if the digit &gt;= 5 otherwise truncated(default).</TD></TR>
<TR><TD>ROUND_HALF_DOWN</TD><TD>round up if the digit &gt;= 6 otherwise truncated.</TD></TR>
<TR><TD>ROUND_HALF_EVEN</TD><TD>round towards the even neighbor(Banker's rounding).
<TR><TD>ROUND_CEILING</TD><TD>round towards positive infinity(ceil).</TD></TR>
<TR><TD>ROUND_FLOOR</TD><TD>round towards negative infinity(floor).</TD></TR>
</TABLE>
nil is returned if any argument is illegal.<BR>
The digit location for rounding operation can not be specified by mode method,
New rounding mode is returned,nil is returned if any argument is not an integer.
Bad specification is ignored.<BR>
The digit location for rounding operation can not be specified by this mode method,
use truncate/round/ceil/floor/add/sub/mult/div mthods for each instance instead.
</BLOCKQUOTE>
@ -286,8 +290,8 @@ of the target digit can be given.<BR>
If n> 0,then the (n+1)th digit counted from the decimal point in fraction part is processed(resulting number of fraction part digits is less than or equal to n).<BR>
If n<0,then the n-th digit counted from the decimal point in integer part is processed(at least n 0's are placed from the decimal point to left).
<CODE><PRE>
c = BigDecimal::new("1.23456").floor(4) # ==> 1.2345
c = BigDecimal::new("15.23456").floor(-1) # ==> 10.0
c = BigDecimal("1.23456").floor(4) # ==> 1.2345
c = BigDecimal("15.23456").floor(-1) # ==> 10.0
</PRE></CODE>
</BLOCKQUOTE>
@ -304,37 +308,33 @@ of the target digit can be given.<BR>
If n>0,then the (n+1)th digit counted from the decimal point in fraction part is processed(resulting number of fraction part digits is less than or equal to n).<BR>
If n<0,then the n-th digit counted from the decimal point in integer part is processed(at least n 0's are placed from the decimal point to left).
<CODE><PRE>
c = BigDecimal::new("1.23456").ceil(4) # ==> 1.2346
c = BigDecimal::new("15.23456").ceil(-1) # ==> 20.0
c = BigDecimal("1.23456").ceil(4) # ==> 1.2346
c = BigDecimal("15.23456").ceil(-1) # ==> 20.0
</PRE></CODE>
</BLOCKQUOTE>
<LI><B>round[(n[,b])]</B></LI><BLOCKQUOTE>
c = a.round<BR>
round a to the nearest 1<>D<BR>
round a to the nearest 1(default)<EFBFBD>D<BR>
<CODE><PRE>
c = BigDecimal("1.23456").round # ==> 1
c = BigDecimal("-1.23456").round # ==> -1
</PRE></CODE>
The rounding operation changes according to BigDecimal::mode(BigDecimal::ROUND_MODE,flag) if specified.
As shown in the following example,an optional integer argument (n) specifying the position
of the target digit can be given.<BR>
If n>0,then the (n+1)th digit counted from the decimal point in fraction part is processed(resulting number of fraction part digits is less than or equal to n).<BR>
If n>0,then the (n+1)th digit counted from the decimal point in fraction part is processed(resulting number of fraction part digits is less than or equal to n).<BR>
If n<0,then the n-th digit counted from the decimal point in integer part is processed(at least n 0's are placed from the decimal point to left).
<CODE><PRE>
c = BigDecimal::new("1.23456").round(4) # ==> 1.2346
c = BigDecimal::new("15.23456").round(-1) # ==> 20.0
</PRE></CODE>
If the second optional argument b is given with the non-zero value(default is zero) then
so called Banker's rounding is performed.<BR>
Suppose the digit p is to be rounded,then:<BR>
If p<5 then p is truncated<BR>
If p>5 then p is rounded up<BR>
If p is 5 then round up operation is taken only when the left hand side digit of p is odd.
Rounding operation can be specified by setting the second optional argument b with the valid ROUND_MODE.<BR>
<CODE><PRE>
c = BigDecimal::new("1.23456").round(3,1) # ==> 1.234
c = BigDecimal::new("1.23356").round(3,1) # ==> 1.234
c = BigDecimal::new("1.23456").round(3,BigDecimal::ROUND_HALF_EVEN) # ==> 1.234
c = BigDecimal::new("1.23356").round(3,BigDecimal::ROUND_HALF_EVEN) # ==> 1.234
</PRE></CODE>
</BLOCKQUOTE>
@ -728,11 +728,11 @@ As +,-,and * are always exact(no round operation is performed unless BigDecimal.
which means more momories are required to keep computation results.
But,the division such as c=1.0/3.0 will always be rounded.<BR>
<H3>2. assign,add,sub,mult,div</H3>
<H3>2. add,sub,mult,div</H3>
The length of the significant digits obtained from +,-,*,/
is always defined by that of right and left side of the operator.
To specify the length of the significant digits by your self,
use methos assign,add,sub,mult,div.
use methos add,sub,mult,div.
<CODE><PRE>
BigDecimal("2").div(3,12) # 2.0/3.0 => 0.6666666666 67E0
</PRE></CODE>