\nIn a previous life, I wrote database software.\nA customer complained that one of their reports was taking an\nunacceptably long amount of time to generate, and I was asked\nto take a look at it even though it wasn’t my account.\n<\/p>\n
\nThe report was a vacation-days report, listing the number of\nvacation days taken and available for each employee. Vacation\ndays accrued at a fixed rate but were granted only in\nquarter-day increments. For example, if you earned 15 vacation\ndays per year and the year was 32% complete, then you had\naccrued 32% × 15 = 4.8 vacation days, of which 4.75 were\navailable to use.\n<\/p>\n
\nThe existing code to round the number of accrued days down to\nthe nearest quarter-day went something like this:\n<\/p>\n
\n* assume that at this point, ACCRUED is the number\n* of accrued days.\nPRIVATE S,F\n* STR(ACCRUED,6,2) converts ACCRUED to a 6-character\n* string: 3 integer digits, a decimal point, and two\n* fractional digits. Excess fractional digits are rounded.\nSTORE STR(ACCRUED,6,2) TO S\nSTORE RIGHT(S,2) TO F && extract digits after decimal\nIF F < "25"\n F = "00" && 00 to 24 becomes 00\nELSE\n IF F < "50"\n F = "25" && 25 to 49 becomes 25\n ELSE\n IF F < "75"\n F = "50" && 50 to 74 becomes 50\n ELSE\n F = "75" && 75 to 99 becomes 75\n ENDIF\n ENDIF\nENDIF\nROUNDED = VAL(LEFT(S,4) + F) && reconstruct value and convert\n<\/pre>\n\nIn other words, the code converted the number to a string,\nextracted the digits after the decimal point, did string comparisons\nto figure out which quartile the fraction resided in, then\ncreated a new string with the replacement fraction and converted\nthat string back to a number.\nAnd all this in an interpreted language.\n<\/p>\n
\nThis code fragment was repeated each time rounding-down was\nneeded because the language supported only 32 subroutines,\nand this procedure wasn’t important enough to be worth kicking\nout one of the other existing subroutines.\n<\/p>\n
\nI replaced this seventeen-line monstrosity with the one-line\nequivalent each time it occurred, and the report ran much faster.\n<\/p>\n