RosettaCodeData/Task/Run-length-encoding/Run-BASIC/run-length-encoding.basic

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string$ = "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
beg = 1
i = 1
[loop]
s$ = mid$(string$,beg,1)
while mid$(string$,i,1) = s$
i = i + 1
wend
press$ = press$ ; i-beg;s$
beg = i
if i < len(string$) then goto [loop]
print "Compressed:";press$
beg = 1
i = 1
[expand]
while mid$(press$,i,1) <= "9"
i = i + 1
wend
for j = 1 to val(mid$(press$,beg, i - beg))
expand$ = expand$ + mid$(press$,i,1)
next j
i = i + 1
beg = i
if i < len(press$) then goto [expand]
print " Expanded:";expand$