ACCEPTED SOLUTION
Accepted Solutions
If you want to ignore the first few values when you chose a value which occurs multiple times in your vector, then the attached file should help.
Concerning your answers: Sure the question about the value which occurs multiple times in the vector was the most important one and I am glad you realized yourself at last that this is a problematic situation.
But as with the others - stating that this or that problematic situation will not occur as you will never enter an input value which has no sign change before, does not help much. In my opinion when programming a function, it must always be exactly determined what should happen in every possible input case. So even though at the moment you do not intend to input an invalid value, it must be defined what the reaction of the program should be if one day you do. The reaction could be a customized error message, or a return value which signals that something unusual had happened (could be a NaN or an invalid index value).
Here is a routine which copes with the most obvious errors and I decided that the function should fail with an appropriate error message without returning any result.
You can find a version which uses if-statements instead of the if functions in the attached sheet.
Without any customized error messages it could be reduced to
and here is yet another, different approach (could be a 1-liner which also works in Prime Express if you don't mind typing "ORIGIN" instead of just "O" five times) - again without error handling (which I still regard as a bad design error):
BTW, you claimed that Luc's approach would not return the index but the value itself. Thats not true! Luc's function "f" returns the index as you demanded. He just showed after calling his function which value would be addressed. His version avoids programming and implements the necessary loops via recursive calls of an if-function. That way his approach also works in Prime Express. Its quite easy to modify his version to fit the new conditions. Additionally I got rid of the function "Sign" and changed the order of the arguments to bring it in line with my functions.
So its up to you now to decide for one of the versions.
If you want to ignore the first few values when you chose a value which occurs multiple times in your vector, then the attached file should help.
Concerning your answers: Sure the question about the value which occurs multiple times in the vector was the most important one and I am glad you realized yourself at last that this is a problematic situation.
But as with the others - stating that this or that problematic situation will not occur as you will never enter an input value which has no sign change before, does not help much. In my opinion when programming a function, it must always be exactly determined what should happen in every possible input case. So even though at the moment you do not intend to input an invalid value, it must be defined what the reaction of the program should be if one day you do. The reaction could be a customized error message, or a return value which signals that something unusual had happened (could be a NaN or an invalid index value).
Here is a routine which copes with the most obvious errors and I decided that the function should fail with an appropriate error message without returning any result.
You can find a version which uses if-statements instead of the if functions in the attached sheet.
Without any customized error messages it could be reduced to
and here is yet another, different approach (could be a 1-liner which also works in Prime Express if you don't mind typing "ORIGIN" instead of just "O" five times) - again without error handling (which I still regard as a bad design error):
BTW, you claimed that Luc's approach would not return the index but the value itself. Thats not true! Luc's function "f" returns the index as you demanded. He just showed after calling his function which value would be addressed. His version avoids programming and implements the necessary loops via recursive calls of an if-function. That way his approach also works in Prime Express. Its quite easy to modify his version to fit the new conditions. Additionally I got rid of the function "Sign" and changed the order of the arguments to bring it in line with my functions.
So its up to you now to decide for one of the versions.
