RosettaCodeData/Task/Digital-root/S-BASIC/digital-root.basic

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rem - return the digital sum of n represented as a string
function digitalsum(nstr = string) = integer
var i, slen, sum = integer
var ch = char
slen = len(nstr)
sum = 0
for i = 1 to slen
ch = mid(nstr, i, 1)
rem - don't process leading or embedded spaces, etc.
if ch >= '0' and ch <= '9' then
sum = sum + (ch - '0')
next i
end = sum
var nstr = string
var droot, pers = integer
0again
rem - input1 does not advance to next line; control-C will exit
input1 "What number"; nstr
droot = digitalsum(nstr)
pers = 1
while droot > 9 do
begin
droot = digitalsum(str$(droot))
pers = pers + 1
end
print " digital root ="; droot; " persistence ="; pers
goto 0again
end