CCBtx Posted March 24, 2018 Share Posted March 24, 2018 I am trying to design a recursive field that will give me an IRR of an investment. To calculate IRR, I have to understand recursion. As a guide, I downloaded this very good example.... but do not understand it, Let( $i = $i + 1 ; Middle( "abcdefghkjilmnopqrstuvwxyz" ; $i ; 1 ) & If ( $i < EndLoop ; ¶ & Test ; Let( $i = "" ; "" ) ) ) Can someone explain to me was "Test" does? I feel silly... but can find no documentation on it. And what does the "Let( $i = "" ; "" )" do? Thanks, #1 Solved... Test is the field name... hence the recursion Link to comment Share on other sites More sharing options...
Fitch Posted March 26, 2018 Share Posted March 26, 2018 FileMaker field calculations cannot be recursive, but they can use a custom function (CF), which can be. In your example it's not exactly clear, but I believe Test would be the name of the CF, and EndLoop would be a parameter of the CF. As such, there's an error, because where it says "Test" after the paragraph mark it's missing its parameter. It should be: Let( $i = $i + 1 ; Middle( "abcdefghkjilmnopqrstuvwxyz" ; $i ; 1 ) & If ( $i < EndLoop ; ¶ & Test(EndLoop) ; Let( $i = "" ; "" ) ) ) If you call the CF like this: Test(3) ... the output will be: a b c As it runs, it increments the counter $i; grabs the $i letter from the string, and then if $i is less than EndLoop -- 3 in this case -- it does it again, by calling itself, which is called recursion. Once $i reaches 4, it goes to the end of the If() function -- Let( $i = "" ; "" ) -- what this does is reset the counter $i and return a null result -- because a Let function has to return something, even if it's only null -- and since it does NOT call itself, the calculation is done. It's always important that a recursive function has some kind of logic like that to tell it when to stop. Hope that helps. PS: you don't have to use a recursive custom function, you could try scripting it. Link to comment Share on other sites More sharing options...
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