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<H2>Control Structures</H2>
<B>Tao</B>'s score language provide a set of constructs for scheduling events
in a performance. These are referred to as <EM>control structures</EM><A NAME="1">
and</A> include the following:
<P><PRE>
At <t>: <body> ...
At <t1> for <t2>: <body> ...
From <t1> to <t2>: <body> ...
Before <t>: <body> ...
After <t>: <body> ...
ControlRate <k>: <body> ...
Every <t>: <body> ...
</PRE>
<P>In each case <CODE><body></CODE> is the code which is to be executed at
the scheduled time. In the case of <CODE>At</CODE><A NAME="2"> the</A> code is executed once
at the given time <CODE><t></CODE>. For <CODE>At..for</CODE><A NAME="3"> and</A> <CODE>From..to</CODE><A NAME="4"> the</A>
<CODE><body></CODE> is executed on every tick in the interval defined by
<CODE><t1></CODE> and <CODE><t2></CODE>.
<P><CODE>Before</CODE><A NAME="5"> and</A> <CODE>After</CODE><A NAME="6"> also</A> define time intervals during which the
<CODE><body></CODE> is executed on every tick but the behaviour is slightly more
context dependent as we will see later in this section. For
<CODE>ControlRate</CODE><A NAME="7"> the</A> code is executed on every <CODE><k></CODE>'th tick and
finally, for <CODE>Every</CODE><A NAME="8"> the</A> code is executed repeatedly once every
<CODE><t></CODE> seconds (other units can be specified).
<P>In each of the control structures introduced above there is a <EM>head</EM><A NAME="9">
part</A> which determines when the <EM>body</EM><A NAME="10"> will</A> be executed. For most of
the control structures the head consists of some sort of test to see what
the value of the system variable <CODE>Time</CODE> is compared to the
given values. This variable keeps track of the amount of sound synthesised
so far - i.e. <EM>performance-time</EM><A NAME="11"> -</A> not real-time.
If the particular condition specified is met then the body of the control
structure is executed.
<P>What follows is a more detailed look at the syntax and behaviour of
the various control structures.
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<tr><td colspan="3" class="addr"><!-- bottom panel --><ADDRESS><FONT SIZE=-1>©1999,2000 Mark Pearson
<A HREF="mailto:m.pearson@ukonline.co.uk">m.pearson@ukonline.co.uk</A> April 30, 2000</ADDRESS><BR></td></tr><!-- end bottom panel --></table></BODY></HTML>
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