File r37/lisp/csl/html/r37_0229.html artifact fac9df8969 part of check-in e1a8550313

<A NAME=WTLEVEL>

<TITLE>WTLEVEL</TITLE></A>
<b><a href=r37_idx.html>INDEX</a></b><p><p>



<B>WTLEVEL</B> _ _ _  _ _ _  _ _ _  _ _ _ <B>command</B><P>
<P>
 
In conjunction with 
<A HREF=r37_0226.html>weight</A>, <em>wtlevel</em> is used to implement 
asymptotic constraints. Its default value is 2. 
 <P> <H3> 
syntax: </H3>
<P>
<P>
<em>wtlevel</em>&lt;expression&gt; 
<P>
<P>
<P>
To change the weight level, &lt;expression&gt; must evaluate to a positive 
integer that is the greatest weight term to be retained in expressions 
involving kernels with weight assignments. <em>wtlevel</em> returns the 
new weight level. If you want the current weight level, but not 
change it, say <em>wtlevel nil</em>. 
<P>
<P>
 <P> <H3> 
examples: </H3>
<P><PRE><TT>
(x+y)**4;          
 

   4      3        2  2        3    4
  X  + 4*X *Y + 6*X *Y  + 4*X*Y  + Y  


weight x=2,y=3; 

wtlevel 8; 

(x+y)**4; 

   4
  X  


wtlevel 10; 

(x+y)**4; 

   2     2            2
  X *(6*Y  + 4*X*Y + X ) 


int(x**2,x); 

  ***** X invalid as KERNEL

</TT></PRE><P><em>wtlevel</em>is used in conjunction with the command 
<A HREF=r37_0226.html>weight</A> to 
enable asymptotic constraints. Weight of a term is computed by multiplying 
the weights of each variable in it by the power to which it has been 
raised, and adding the resulting weights for each variable. If the weight 
of the term is greater than <em>wtlevel</em>, the term is dropped from the 
expression, and not used in any further computation involving the 
expression. 
<P>
<P>
Once a weight has been attached to a 
<A HREF=r37_0002.html>kernel</A>, it is no longer 
recognized by the system as a kernel, though still a variable. It cannot 
be used in REDUCE commands and operators that need kernels. The weight 
attachment can be undone with a 
<A HREF=r37_0189.html>clear</A> command. <em>wtlevel</em> can 
be changed as desired. 
<P>
<P>
<P>