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+1. This is structured programming, applied to concurrent setting. The argument for structured programming was made and won in the '60s [0]. It is amazing that

by pacala 9y ago

+1. This is structured programming, applied to concurrent setting. The argument for structured programming was made and won in the '60s [0]. It is amazing that we keep making the same mistakes over and over again. > The unbridled use of the go to statement has an immediate consequence that it becomes terribly hard to find a meaningful set of coordinates in which to describe the process progress. Usually, people take into account as well the values of some well chosen variables, but this is out of the question because it is relative to the progress that the meaning of these values is to be understood! With the go to statement one can, of course, still describe the progress uniquely by a counter counting the number of actions performed since program start (viz. a kind of normalized clock). The difficulty is that such a coordinate, although unique, is utterly unhelpful. In such a coordinate system it becomes an extremely complicated affair to define all those points of progress where, say, n equals the number of persons in the room minus one! [0] http://www.u.arizona.edu/~rubinson/copyright_violations/Go_To_Considered_Harmful.html http://www.u.arizona.edu/~rubinson/copyright_violations/Go_T...

cwzwarich 9y ago
> The argument for structured programming was made and won in the '60s Most code out there is fine using break and continue in loops, and early returns are pretty popular. All of these are unstructured programming (by the 60s definition). I don't think it's all that clear that it has won.
- scott_s 9y ago
  The author anticipates this point, and rebuts it: "In the end, modern languages are a bit less strict about this than Dijkstra's original formulation. They'll let you break out of multiple nested structures at once using constructs like break, continue, or return. But fundamentally, they're all designed around Dijkstra's idea; even these constructs that push the boundaries do so only in strictly limited ways. In particular, functions – which are the fundamental tool for wrapping up control flow inside a black box – are considered inviolate. You can't break out of one function and into another, and a return can take you out of the current function, but no further. Whatever control flow shenanigans a function gets up to internally, other functions don't have to care. This even extends to goto itself. You'll find a few languages that still have something they call goto, like C, C#, Golang, ... but they've added heavy restrictions. At the very least, they won't let you jump out of one function body and into another. Unless you're working in assembly, the classic, unrestricted goto is gone. Dijkstra won." I tend to agree with the author. Linux kernel code, for example, uses goto for error handling, particularly when implementing system calls. But the author is correct: the gotos can't jump out of the function. Readers can still infer control flow from function call sequences. I quite enjoyed the post, I think it's worth giving the author's claims serious consideration.
- mannykannot 9y ago
  Putting aside pedantic purity arguments, structured programming has come to dominate high-level-language design and the way we think of programming. Programs like the FLOW-MATIC example from the article are simply not being written any more in any HLL. Few (if any) concepts have achieved greater ubiquity.

by pacala 9y ago

cwzwarich 9y ago

> The argument for structured programming was made and won in the '60s Most code out there is fine using break and continue in loops, and early returns are pretty popular. All of these are unstructured programming (by the 60s definition). I don't think it's all that clear that it has won.

scott_s 9y ago
The author anticipates this point, and rebuts it: "In the end, modern languages are a bit less strict about this than Dijkstra's original formulation. They'll let you break out of multiple nested structures at once using constructs like break, continue, or return. But fundamentally, they're all designed around Dijkstra's idea; even these constructs that push the boundaries do so only in strictly limited ways. In particular, functions – which are the fundamental tool for wrapping up control flow inside a black box – are considered inviolate. You can't break out of one function and into another, and a return can take you out of the current function, but no further. Whatever control flow shenanigans a function gets up to internally, other functions don't have to care. This even extends to goto itself. You'll find a few languages that still have something they call goto, like C, C#, Golang, ... but they've added heavy restrictions. At the very least, they won't let you jump out of one function body and into another. Unless you're working in assembly, the classic, unrestricted goto is gone. Dijkstra won." I tend to agree with the author. Linux kernel code, for example, uses goto for error handling, particularly when implementing system calls. But the author is correct: the gotos can't jump out of the function. Readers can still infer control flow from function call sequences. I quite enjoyed the post, I think it's worth giving the author's claims serious consideration.
mannykannot 9y ago
Putting aside pedantic purity arguments, structured programming has come to dominate high-level-language design and the way we think of programming. Programs like the FLOW-MATIC example from the article are simply not being written any more in any HLL. Few (if any) concepts have achieved greater ubiquity.