Functions Palette/Programming/Structures/Stacked Sequence Structure

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Stacked Sequence Structure

A Stacked Sequence Structure, or SSS, is a set of subdiagrams represented by numerical indices that executes in order of the indices. Since LabVIEW 2014 it has been removed from the Structures palette and is considered deprecated. However, due to software in older versions of LabVIEW using the structure, it has not been removed from the development environment nor from the run-time engine. Therefore, the code will still show the stacked sequence structure where used.

In most cases better code organization (including SubVIs, proper design patterns, and/or frameworks) will negate the need for a stacked sequence structure. In some cases where sequential code execution is still necessary, it can be handled using the squencer pattern variation of the state machine design pattern. The exact reasoning why the sequencer pattern can be argued to be better is due to its extensibility and readability over the stacked sequence structure.

The stacked sequence structure has some severe disadvantages with the three most prominent:[1]

  1. Passing data from "case" to "case" requires sequence locals. These are no-gos for code design.
  2. You can see only a fraction of code at one view. While this is true for other structures (case, event), the SSS does not provide the flexibility and power of the other structures.
  3. Speaking of flexibility: The SSS has a strict order of execution. If you want to swap "cases", you often have VERY much to do in the code to make it work. Adding new "cases" is also very often close to nightmare.

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