This is documentation for Mathematica 8, which was
based on an earlier version of the Wolfram Language.

# ComplexityFunction

 ComplexityFunctionis an option for Simplify and other functions which gives a function to rank the complexity of different forms of an expression.
• With the default setting ComplexityFunction, forms are ranked primarily according to their LeafCount, with corrections to treat integers with more digits as more complex.
• Simplify applies f to each intermediate expression generated by Simplify, treating the one which yields the smallest numerical value as simplest.
The default ComplexityFunction counts the subexpressions and digits of integers:
LeafCount counts only the number of subexpressions:
By default this expression is not simplified:
This complexity function makes ChebyshevT more expensive than other functions:
The default ComplexityFunction counts the subexpressions and digits of integers:
 Out[1]=
LeafCount counts only the number of subexpressions:
 Out[2]=

By default this expression is not simplified:
 Out[1]=
This complexity function makes ChebyshevT more expensive than other functions:
 Out[3]=
 Scope   (1)
With the default ComplexityFunction, Abs[x] is simpler than the FullForm of -x:
This complexity function counts characters in the InputForm of the expression:
Now -x is simpler than Abs[x]:
The automatic complexity function:
New in 3