gm@keysec.kse.com (Greg McGary) (12/20/89)
Quattro (Borland's answer to Lotus-123) has the fatal flaw of not having adequate built-in formulas for calculating mortgage amortizations with balloon payments. What I want are built-in `five-banger' formulas that work like the HP-12C calculator. Like so: @n(i, pv, pmt, fv) @i(n, pv, pmt, fv) @pv(n, i, pmt, fv) @pmt(n, i, pv, fv) @fv(n, i, pv, pmt) If I knew enough about the innards of Quattro, I would patch the binary to add these in. My manual says that Quattro hosts cridders called `add-ins' that sound like patches done in some `official' way. Does anyone out in net-land have any experience with `add-ins', or happen to know how I might go about adding HP-12C style mortgage-amortization features to Quattro (or Lotus-123 for that matter)? BTW, I've already worked out the hairy math for doing all but one function with expressions. This is not the preferred solution though, since it can be a lot of typing. In case anyone is interested, here they are: n = @LN((pmt - fv * i) / (pmt + pv * i)) / @LN(1 + i) pv = (pmt - fv * i) / ((1 + i)^n * i) - (pmt / i) pmt = (i * (pv * (1 + i)^n + fv)) / (1 - (1 + i)^n) fv = (pmt - (pmt + pv * i) * (1 + i)^n) / i i = <give this one a try, I can't figure it out...> Thanks in advance for all leads. Please respond via mail if possible. -- -- Greg McGary -- 10310 Main Street, #109, Fairfax, VA 22030; (703) 352-0407 -- gm@kse.com, gm@cs.duke.edu, ..!uunet!keysec!gm