An IFn function takes an argument expression (Arg) and checks in which of predefined value intervals [–∞ – Е1; Е1 – Е2; Е2 – Е3, ... ; Еn – Еn+1; Еn+1 – ∞] it falls. It then returns the result value [R1, R2, ..., Rn+2] from a predefined set of results that corresponds to the respective value interval. That is, R2 is returned if Е1 < Arg ≤ Е2.
The IFn function pattern may have two situations:
In this case, IFn functions have:
The pattern of an IFn function is as follows:
IFn (Arg, E1, E2, E3 ..., En+1, R1, R2, R3, ..., Rn+2) (Here result values are entered for all predefined value intervals.)
In visual terms, this is shown in the following picture:
| IF1 function: IF1(Arg, E1, E2, R1, R2, R3) | |
| IF3 function: IF3(Arg, E1, E2, E3, E4, R1, R2, R3, R4, R5) | |
Consider the following example:
A=IF1(Arg, 3, 7, 10, 15, 20)
In the above case:
| FOR | A IS |
|---|---|
| Arg = 3 | 10 |
| 3 < Arg ≤ 7 | 15 |
| 7 < Arg | 20 |
In this case IFn functions have:
NOTE: For the first and last value intervals, the program returns zero.
The pattern of an IFn function is as follows:
IFn (Arg, E1, E2, E3 ..., En+1, R1, R2, R3, ..., Rn) (Here, no result values are entered for the first and the last value intervals.)
IFn functions are appropriate when parameters depend on other parameter — for example, we can create a dependence between the length of a box and the width of the glue flap. Consider the following example:
We have a regular rectangular box with a parameter A for the length of the body and a parameter GL for the glue flap width:
| WHEN | GL Should Take |
|---|---|
| A ≤ 100 | 10 |
| 100 < A < 200 | 15 |
| A > 200 | 20 |
GL will take the values from the function IF1(A, 100, 200, 10, 15, 20), which we enter in its expression.
