Thanks heaps - it certainly is a mental block with me.
And thanks for the great, informative reply - I'm already looking forward
to the "next installment"
Many thanks
Seamus
At 12:45 pm 13/07/01 , you wrote:
>Seamus
>
>Some people take to the concepts of loops naturally... for others it
>is a mental block.
>
>Not to worry!
>
>The classic programming problem which illustrates the need for loops
>is the "Native American" Problem:
>
> The Dutch purchased Manhattan Island from the "Native Americans"
>for $18.00 in
> er, ah... lets say 1624. If the money were invested at 4%, compounded
> annually, what would it be worth today.
>
>To solve you could write out:
>
> Year: 1624 Value: $18.00
> Year: 1625 Value: $18.00 * 1.04
> Year: 1626 Value: $18.00 * 1.04 * 1.04
> .
> .
> .
>
>so we would do the 375 steps to get to 2001
>
>Now if we look closely, we notice a certain consistency in the
>operations performed in each step:
>
> the year is incremented by 1
>
> the amount is incremented by 4& ( Amount * 1.04 )
>
>Regardless of which step (year) the calculations are always the
>same... the 2 operations are repeated over and over.
>
>To write this out abstractly we could say:
>
> Start with an amount of $18,00
>
> Start at a year of 1624
>
> Repeat
>
> Add 1 to the year
>
> Multiply the amount by 1.04
>
> until the year is equal to 2001
>
>What controls the number of times we repeat, is the year (incremented)
>
>
>Now, we take this and rewrite this in CF"
>
> <cfset amount=18.00>
>
> <cfloop index=theYear from=1624 to=2001 step=1>
>
> <cfset amount = amount * 1.04>
>
> <cfloop>
>
>Now if you compare the two, you see that the <cfloop> tag combines
>the operations of:
>
> setting the starting and ending values for year
>
> setting the increment for year
>
> testing for the end value of year.
>
>So all we have to do is compute the amount and indicate the end of the loop.
>
>Now, if you change the problem slightly:
>
> The Dutch purchased Manhattan Island from the "Native Americans"
>for $18.00 in
> er, ah... lets say 1624. If the money were invested at 4%, compounded
> annually, when would the value exceed $200,000?
>
>.... we'll cover that in the next installment,
>
>HTH
>
>Dick
>
>
>At 11:17 AM +1000 7/13/01, Seamus Campbell wrote:
> >Many thanks again.
> >
> >Slightly OT - I have learnt CF without any background in programming - I
> >have a huge problem getting loops and lists to work - I can understand the
> >general principles but just can't seem to be able to learn to implement
> >specific code.
> >
> >For instance I can see what you are doing in the code below and I can adapt
> >code that other people have done (often by trial and error rather than
> logic)
> >BUT i have huge problems coding loops and lists on my own.
> >
> >Is this normal - or am I just slow???
> >
> >Any ways to learn how to "roll my own" ???
> >
> >Many thanks
> >Seamus
> >
>
>
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