This is documentation for Mathematica 8, which was
based on an earlier version of the Wolfram Language.
 BUILT-IN MATHEMATICA SYMBOL

# TraceScan

 TraceScanapplies f to all expressions used in the evaluation of expr. TraceScanincludes only those expressions which match form. TraceScanincludes all evaluations which use transformation rules associated with the symbol s. TraceScanapplies f before evaluation and fp after evaluation to expressions used in the evaluation of expr.
• All expressions are wrapped in HoldForm to prevent evaluation before f or fp are applied to them.
• The function fp is given as an argument for both the form before evaluation and the form after evaluation.
• TraceScan returns the result of evaluating expr.
Print all expressions used for evaluation:
Count additions and multiplications of machine numbers needed for a numerical computation:
A recursive definition for finding Fibonacci numbers:
Count calls to required:
Redefine so that it saves results:
Count calls to required:
The second time through it takes only one call since the value was saved:
Print all expressions used for evaluation:
 Out[1]=

Count additions and multiplications of machine numbers needed for a numerical computation:
 Out[1]=

A recursive definition for finding Fibonacci numbers:
Count calls to required:
 Out[2]=
Redefine so that it saves results:
Count calls to required:
 Out[4]=
The second time through it takes only one call since the value was saved:
 Out[5]=
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