Thanks to the help the other day with the strange concatentation result.
I was referring to a BF interpreter I was working on, in pure SQLite SQL.
Well, here it is, working.
Hopefully no-one finds this useful,
Gary
WITH RECURSIVE
program AS
(SELECT
'++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.'
AS p,
'' AS input, 3 AS width
),
jumpdepth AS
(SELECT 0 AS idx, 0 AS jumpdepth, '' AS jumplist, NULL as jumpback, NULL
AS direction, p || '0' AS p, width FROM program
UNION ALL
SELECT idx+1, CASE SUBSTR(p, idx+1, 1)
WHEN '[' THEN jumpdepth+1
WHEN ']' THEN jumpdepth-1
ELSE jumpdepth END,
CASE SUBSTR(p, idx+1, 1)
WHEN '[' THEN SUBSTR('0000000' || (idx+1), -width) || jumplist
WHEN ']' THEN SUBSTR(jumplist,width+1)
ELSE jumplist END,
CASE SUBSTR(p, idx+1, 1)
WHEN ']' THEN CAST(SUBSTR(jumplist,1,width) AS INTEGER)
ELSE NULL END,
CASE SUBSTR(p, idx+1, 1)
WHEN '[' THEN 'L'
WHEN ']' THEN 'R'
ELSE NULL END,
p, width
FROM jumpdepth
WHERE LENGTH(p)>=idx),
jumptable(a,b,dir) AS
(SELECT idx,jumpback,'L' FROM jumpdepth WHERE jumpback IS NOT NULL
UNION ALL
SELECT jumpback,idx+1,'R' FROM jumpdepth WHERE jumpback IS NOT NULL),
bf(ep, p, width, defaulttapeentry, ip, dp, instruction, output, input, tape)
AS
(SELECT 0, p, width, SUBSTR('0000000', -width), 1, 1, '', '', input,
SUBSTR('000000', -width)
FROM program
UNION ALL
SELECT ep+1, p, width, defaulttapeentry, CASE WHEN jumptable.b IS NOT
NULL AND
((dir='R' AND CAST(SUBSTR(tape, width*(dp-1)+1, width) AS
INTEGER)=0)
OR
(dir='L' AND CAST(SUBSTR(tape, width*(dp-1)+1, width) AS
INTEGER)!=0)) THEN jumptable.b
ELSE ip+1 END,
CASE SUBSTR(p, ip, 1)
WHEN '>' THEN dp+1
WHEN '<' THEN MAX(dp-1,1)
ELSE dp END,
SUBSTR(p, ip, 1),
CASE WHEN SUBSTR(p, ip, 1)='.' THEN (output || CHAR(SUBSTR(tape,
(dp-1)*width+1, width))) ELSE output END,
CASE WHEN SUBSTR(p, ip, 1)=',' THEN SUBSTR(input, 2) ELSE input END,
CASE SUBSTR(p, ip, 1)
WHEN '<' THEN CASE WHEN dp=1 THEN defaulttapeentry || tape ELSE
tape END
WHEN '>' THEN CASE WHEN dp*width=LENGTH(tape) THEN tape ||
defaulttapeentry ELSE tape END
WHEN '+' THEN SUBSTR(tape,1,width*(dp-1)) || SUBSTR('0000000'
|| (CAST(SUBSTR(tape,width*(dp-1)+1,width) AS INTEGER)+1), -width) ||
SUBSTR(tape,width*dp+1)
WHEN '-' THEN SUBSTR(tape,1,width*(dp-1)) || SUBSTR('0000000'
|| (CAST(SUBSTR(tape,width*(dp-1)+1,width) AS INTEGER)-1), -width) ||
SUBSTR(tape,width*dp+1)
WHEN ',' THEN SUBSTR(tape,1,width*(dp-1)) || SUBSTR('0000000'
|| (UNICODE(SUBSTR(input,1,1))), -width) || SUBSTR(tape,width*(dp+1))
ELSE tape END
FROM bf LEFT JOIN jumptable ON jumptable.a=ip WHERE LENGTH(p) >= ip)
SELECT output FROM bf ORDER BY ep DESC LIMIT 1;
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