Source code in the zkl programming language

fcn entropy(text){
   text.pump(Void,fcn(c,freq){ c=c.toAsc(); freq[c]=freq[c]+1; freq }
       .fp1((0).pump(256,List,(0.0).create.fp(0)).copy()))
   .filter()		      // remove all zero entries
   .apply('/(text.len()))     // (num of char)/len
   .apply(fcn(p){-p*p.log()}) // |p*ln(p)|
   .sum(0.0)/(2.0).log();     // sum * ln(e)/ln(2) to convert to log2
}

entropy(File("entropy.zkl").read().text).println();