Solution to TSQL Challenge 48 - Parse and evaluate Arithmetic Expressions using TSQL By durk

;WITH     C (id, expr, v, q, s, x, r, t, w, l, i, n)
AS       (SELECT id,
				 expr,
				 x0 + (dx * n),
				 CAST ('' AS VARCHAR (8000)),
				 CAST ('' AS VARCHAR (8000)),
				 CAST ('' AS VARCHAR (8000)),
				 CAST ('' AS VARCHAR (8000)),
				 '(',
				 REPLACE(expr, ' ', '') + ')',
				 0,
				0, 
				 CAST (0 AS FLOAT (53))
		  FROM   Tsqlc_Tally AS t WITH (NOLOCK)
				 INNER JOIN
				 TC48 AS c WITH (NOLOCK)
				 ON t.N < c.points
		  UNION ALL
		  SELECT id,
				 expr,
				 v,
				 q + CASE t WHEN '^' THEN LEFT(s, PATINDEX('%[(*/+--]%', s) - 1) WHEN '*' THEN LEFT(s, PATINDEX('%[(+--]%', s) - 1) WHEN '/' THEN LEFT(s, PATINDEX('%[(+--]%', s) - 1) WHEN '+' THEN LEFT(s, CHARINDEX(CHAR(40), s) - 1) WHEN '-' THEN LEFT(s, CHARINDEX(CHAR(40), s) - 1) WHEN ')' THEN LEFT(s, CHARINDEX(CHAR(40), s) - 1) WHEN '(' THEN '' WHEN '' THEN '' WHEN 'X' THEN CAST (V AS VARCHAR (8000)) + CHAR(32) ELSE t + ' ' END,
				 CASE ASCII(t) WHEN 94 THEN '^ ' + SUBSTRING(s, PATINDEX('%[(*/+--]%', s), l) WHEN 42 THEN '* ' + SUBSTRING(s, PATINDEX('%[(+--]%', s), l) WHEN 47 THEN '/ ' + SUBSTRING(s, PATINDEX('%[(+--]%', s), l) WHEN 43 THEN '+ ' + SUBSTRING(s, CHARINDEX(CHAR(40), s), l) WHEN 45 THEN '- ' + SUBSTRING(s, CHARINDEX(CHAR(40), s), l) WHEN 40 THEN '( ' + s WHEN 41 THEN SUBSTRING(s, CHARINDEX(CHAR(40), s) + 2, l) ELSE s END,
				 SUBSTRING(q, i + 1, NULLIF (CHARINDEX(CHAR(32), q, i + 1), 0) - i - 1),
				 CASE WHEN x IS NULL THEN r WHEN CHARINDEX(x, '*/+-^') = 0 THEN CONVERT(VARCHAR(8000), n, 2) + CHAR(32) + r ELSE RIGHT(r, 1 + LEN(r) - CHARINDEX(CHAR(32), r)) END,
				 LEFT(w, 1),
				 LTRIM(SUBSTRING(w, 2, LEN(w))),
				 LEN(s),
				 ISNULL(NULLIF (CHARINDEX(CHAR(32), q, i + 1), 0), DATALENGTH(q)),
				 n = CASE ISNULL(x, '') WHEN '' THEN n WHEN '^' THEN POWER(CAST (LEFT(r, CHARINDEX(CHAR(32), r)) AS FLOAT (53)), n) WHEN '*' THEN CAST (LEFT(r, CHARINDEX(CHAR(32), r)) AS FLOAT (53)) * n WHEN '/' THEN CAST (LEFT(r, CHARINDEX(CHAR(32), r)) AS FLOAT (53)) / n WHEN '+' THEN CAST (LEFT(r, CHARINDEX(CHAR(32), r)) AS FLOAT (53)) + n WHEN '-' THEN CAST (LEFT(r, CHARINDEX(CHAR(32), r)) AS FLOAT (53)) - n ELSE cast(x as float(53)) END
		  FROM   C
		  WHERE  NOT (t = ''
					  AND x IS NULL))
SELECT   expr,
		 v AS x,
		 n AS value
FROM     C
WHERE    t = ''
		 AND x IS NULL
ORDER BY expr, v
OPTION (MAXRECURSION 0);

Performance stats of the above solution

Sr# StartTime                 Reads      Writes         CPU Duration 
--- ------------------- ----------- ----------- ----------- -------- 
  1 Mar 26 2011  2:21PM      974098          75        4203    4.308
  2 Mar 26 2011  2:23PM      974077          75        4110    4.292
  3 Mar 26 2011  2:24PM      974077          75        4140    4.292
  4 Mar 26 2011  2:25PM      974087          76        4078    4.281
  5 Mar 26 2011  2:26PM      974087          76        4094    4.293