A challenge: adding months to a date?

[David Bovill]

Getting there :)

But still fails the unit tests - resulting in:

1
Failed adding 1 to 2002,1,31,1,0,0,5. Resulted in 1
2
Failed adding 2 to 2002,1,31,1,0,0,5. Resulted in 2
4
5
6
7
8
9
10
10
Failed adding 10 to 2002,1,31,1,0,0,5. Resulted in 10

Which looks like is kind of one out of the loop - NB I like your evaluation
of leap years - is that all there is to it? Taking a look at the code now to
see where it is going wrong...


on mouseUp
    -- unit test

    put "2002,1,31,1,0,0,5" into abbeyStartDate
    put 1 into lastMonth
    repeat with statementNumber = 1 to 10
        put item 2 of date_AddMonth(statementNumber, abbeyStartDate) into
someMonth
        put someMonth
        if statementNumber mod 12 is not (someMonth - 1) then
            put merge("Failed adding [[statementNumber]] to
[[abbeyStartDate]]. Resulted in [[someMonth]]")
        end if
    end repeat
end mouseUp

function date_AddMonth monthNum, startDate
    convert startDate to dateItems    # does not work if startDate is a
system date
    put item 3 of startDate into theDay
    put 1 into item 3 of startDate
    add monthNum to item 2 of startDate
    convert startDate from dateItems to dateItems
    put item 2 of startDate into theMonth
    put item 1 of startDate into theYear
    put getMaxDays(theMonth, theYear) into maxDay
    if theDay > maxDay then
        put maxDay into theDay
    end if
    put theDay into item 3 of startDate
    --convert startDate from dateItems to <favorite date format>
    return startDate
end date_AddMonth

function getMaxDays theMonth, theYear
    put "1,January,3,March,5,May,7,July,8,August,10,October,12,December"
into Months31
    put "4,April,6,June,9,September,11,November" into Months30
    if theMonth is among the items of Months31 then
        put 31 into HowManyDays
    else if theMonth is among the items of Months30 then
        put 30 into HowManyDays
    else --February
        if (theYear mod 400 = 0) or (theYear mod 100 <> 0) and (theYear mod
4 = 0) then
            put 29 into HowManyDays -- leap year
        else
            put 28 into HowManyDays
        end if
    end if
    return HowManyDays
end getMaxDays