WTLEVEL _ _ _ _ _ _ _ _ _ _ _ _ command

In conjunction with weight, wtlevel is used to implement asymptotic constraints. Its default value is 2.

syntax:

wtlevel<expression>

To change the weight level, <expression> must evaluate to a positive integer that is the greatest weight term to be retained in expressions involving kernels with weight assignments. wtlevel returns the new weight level. If you want the current weight level, but not change it, say wtlevel nil.

examples:

(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

wtlevelis used in conjunction with the command weight 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 wtlevel, the term is dropped from the expression, and not used in any further computation involving the expression.

Once a weight has been attached to a kernel, 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 clear command. wtlevel can be changed as desired.