anchor.diff:  spectralnorm
   health
   raytracer
  -binarytrees,
  +binarytrees
   implicitode,
   dispatch,
   
  
positive.code: process,
  message,
  takfp,
  nsieve
  nsievebits
  fannkuch
  pidigits
  
negative.code: wc,count-words
  heapsort,heapsort
  methcall,methods
  random,random
  regexmatch,regex
  spellcheck,spellcheck
  