RosettaCodeData/Task/Run-length-encoding/Zkl/run-length-encoding-1.zkl

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const MAX_LEN=250, MIN_LEN=3;
fcn compress(text){ // !empty byte/text stream -->Data (byte stream)
sink:=Data(); cnt:=Ref(0);
write:='wrap(c,n){ // helper function
while(n>MAX_LEN){
sink.write(1); sink.write(MAX_LEN); sink.write(c);
n-=MAX_LEN;
}
if(n>MIN_LEN){ sink.write(1); sink.write(n); sink.write(c); }
else { do(n) { sink.write(c); } }
};
text.reduce('wrap(a,b){
if(a==b) cnt.inc();
else{ write(a,cnt.value); cnt.set(1); }
b
},text[0]) : write(_,cnt.value);
sink;
}