2.8.htm

RUBY的参考手册~~ RUBY的参考手册~~RUBY的参考手册

                  <TT><I>conditional</I></TT> is <TT>true</TT>.</P><PRE>begin <TT><I>code</I></TT> end while <TT><I>conditional</I></TT></PRE>
                  <P class=docText>If a <TT>while</TT> modifier follows a 
                  <TT>begin</TT> statement with no <TT>rescue</TT> or 
                  <TT>ensure</TT> clauses, <TT><I>code</I></TT> is executed once 
                  before <TT><I>conditional</I></TT> is evaluated. </P><A 
                  name=ch02-66-fm2xml></A><A name=IXT-2-127056></A><A 
                  name=IXT-2-127057></A><A name=IXT-2-127058></A>
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                    <TR>
                      <TD align=left><B><I>until Statement</I></B></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
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                      <TD align=left><PRE>until <TT><I>conditional</I></TT> [do]
<TT><I>code</I></TT>
end</PRE><PRE><TT><I>code</I></TT> until<TT><I>conditional</I></TT></PRE><PRE>begin 
<TT><I>code</I></TT>
end until <TT><I>conditional</I></TT></PRE></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
                  <P class=docText><A name=IXT-2-127057></A><A 
                  name=IXT-2-127058></A>Executes <TT><I>code</I></TT> while 
                  <TT><I>conditional</I></TT> is <TT>false</TT>. An 
                  <TT>until</TT> statement's <TT><I>conditional</I></TT> is 
                  separated from code by the reserved word <TT>do</TT>, a 
                  newline, or a semicolon. Like <TT>while</TT>, <TT>until</TT> 
                  can be used as statement modifier.</P>
                  <P class=docText>Executes<TT><I>code</I></TT> while 
                  <TT><I>conditional</I></TT> is <TT>false</TT>.</P>
                  <P class=docText>If an <TT>until</TT> modifier follows a 
                  <TT>begin</TT> statement with no <TT>rescue</TT> or 
                  <TT>ensure</TT> clauses, <TT><I>code</I></TT> is executed once 
                  before <TT><I>conditional</I></TT> is evaluated. </P><A 
                  name=ch02-67-fm2xml></A><A name=IXT-2-127059></A><A 
                  name=IXT-2-127060></A><A name=IXT-2-127061></A><A 
                  name=IXT-2-127062></A><A name=IXT-2-127063></A>
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                    <TBODY>
                    <TR>
                      <TD align=left><B><I>for Statement</I></B></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
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                      <TD align=left><PRE>for <TT><I>variable</I></TT>[, <TT><I>variable</I></TT>...] in <TT><I>expression</I></TT> [do]
<TT><I>code</I></TT>
end</PRE></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
                  <P class=docText><A name=IXT-2-127060></A><A 
                  name=IXT-2-127061></A><A name=IXT-2-127062></A><A 
                  name=IXT-2-127063></A>Executes <TT><I>code</I></TT> once for 
                  each element in <TT><I>expression</I></TT>. Almost exactly 
                  equivalent to: </P><PRE>expression.each do |variable[, variable...]| code end</PRE>
                  <P class=docText>except that a <TT>for</TT> loop doesn't 
                  create a new scope for local variables. A <TT>for</TT> loop's 
                  <TT><I>expression</I></TT> is separated from 
                  <TT><I>code</I></TT> by the reserved word <TT>do</TT>, a 
                  newline, or a semicolon. </P><A name=ch02-68-fm2xml></A><A 
                  name=IXT-2-127064></A><A name=IXT-2-127065></A><A 
                  name=IXT-2-127066></A><A name=IXT-2-127067></A>
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                    <TR>
                      <TD align=left><B><I>break Statement</I></B></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
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                      <TD align=left><PRE>break</PRE></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
                  <P class=docText><A name=IXT-2-127065></A><A 
                  name=IXT-2-127066></A><A name=IXT-2-127067></A>Terminates a 
                  <TT>while</TT>/<TT>until</TT> loop. Terminates a method with 
                  an associated block if called within the block (with the 
                  method returning <TT>nil</TT>). </P><A 
                  name=ch02-69-fm2xml></A><A name=IXT-2-127068></A><A 
                  name=IXT-2-127069></A><A name=IXT-2-127070></A><A 
                  name=IXTR3-6></A>
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                    <TR>
                      <TD align=left><B><I>next Statement</I></B></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
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                      <TD align=left><PRE>next</PRE></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
                  <P class=docText><A name=IXT-2-127069></A><A 
                  name=IXT-2-127070></A>Jumps to the point immediately before 
                  the evaluation of a loop's conditional. Terminates execution 
                  of a block if called within a block (with <TT>yield</TT> or 
                  call returning <TT>nil</TT>).<A name=IXTR3-6></A> </P><A 
                  name=ch02-70-fm2xml></A><A name=IXT-2-127071></A><A 
                  name=IXT-2-127072></A>
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                    <TBODY>
                    <TR>
                      <TD align=left><B><I>redo Statement</I></B></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
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                    <TR>
                      <TD align=left><PRE>redo</PRE></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
                  <P class=docText><A name=IXT-2-127072></A>Jumps to the point 
                  immediately after the evaluation of the loop's conditional. 
                  Restarts <TT>yield</TT> or <TT>call</TT> if called within a 
                  block. </P><A name=ch02-71-fm2xml></A><A 
name=IXT-2-127073></A>
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                      <TD align=left><B><I>retry Statement</I></B></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
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                      <TD align=left><PRE>retry</PRE></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
                  <P class=docText>Repeats a call to a method with an associated 
                  block when called from outside a <TT>rescue</TT> clause. </P>
                  <P class=docText>Jumps to the top of a 
                  <TT>begin</TT>/<TT>end</TT> block if called from within a 
                  <TT>rescue</TT> clause. </P><A name=ch02-72-fm2xml></A><A 
                  name=IXT-2-127074></A><A name=IXT-2-127075></A><A 
                  name=IXT-2-127076></A><A name=IXT-2-127077></A><A 
                  name=IXT-2-127078></A><A name=IXT-2-127079></A><A 
                  name=IXT-2-127080></A><A name=IXT-2-127081></A><A 
                  name=IXT-2-127082></A><A name=IXT-2-127083></A><A 
                  name=IXT-2-127084></A>
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                    <TR>
                      <TD align=left><B><I>begin Statement</I></B></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
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                      <TD align=left><PRE>begin 
<TT><I>code</I></TT>
[rescue [<TT><I>exception_class</I></TT>[, <TT><I>exception_class</I></TT>...]] [=&gt; <TT><I>variable</I></TT>] [then]
<TT><I>code</I></TT>]...
[else
<TT><I>code</I></TT>]
[ensure
<TT><I>code</I></TT>]
end</PRE></TD>
                      <TD align=right></TD></TR></TBODY></TABLE>
                  <P class=docText><A name=IXT-2-127075></A><A 
                  name=IXT-2-127076></A><A name=IXT-2-127077></A>The