Single entry single exit blocks

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1. Single entry single exit blocks

SESE (Single Entry Single Exit) code blocks are important for program correctness and understanding and reasoning about the behavior of program code.

Almost any group of contiguous statements can be (mentally) considered a block.

KISS = Keep It Simple Stupid.

2. Violating block structure

SESE blocks with one way in and one way out have many advantages in reasoning about programs.
Some (useful) commands violate SESE blocks structure.

break (in loops)
continue (in loops, not in Lua)
return (in functions, not in Lua at top level)
goto (if allowed or supported, does Java have goto?)

These should be localized so that on outer block can be conceptualized. There should be only one way in and one way out of a block.

3. Structured programming

In his book Structured programming (1975), Nicklaus Wirth, inverter of the Pascal programming language, popularized the idea of "structured programming" where programs consisted of a hierarchy of single-entry single exit blocks without using the goto statement.

More: Niklaus Wirth

4. Goto controversy

As part of the "structured programming" movement in programming, Dijkstra started the controversy/war in 1968 that raged for more than 20 years and has not ended to this day. His letter to the editor was entitled
"Go to statement considered harmful".

More: Edsger Dijkstra

KISS = Keep It Simple Stupid

SESE (Single Entry Single Exit)

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