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TeX was Knuth's first “real” programming in a few years. His comments on structured programming are a bit eyebrow raising. He had high praise for it and said th

by dhosek 5y ago

TeX was Knuth's first “real” programming in a few years. His comments on structured programming are a bit eyebrow raising. He had high praise for it and said that it allowed him to write the whole program without having to test small parts of the program (the book with the exact quote is upstairs and I'm too lazy to go get it). That said, I'm pretty sure that TeX is more than a 1000 lines of code.

nine_k 5y ago
Often functional tests provide more bang for the buck than unit tests. Concentrating on functional tests allows to move faster. This is because most modern languages allow you to write in structural style which is impossible to get wrong without noticing. If you have a loop, you know it repeats for its condition, and does not otherwise. If you have a `then` clause, you know it will only run when the `if` condition is true. If you have a function, you know it's only computed when called. Compare it to pre-structural languages like Fortran IV or Basic, where you can freely jump into the middle of the loop, inside of what constitutes an undelimited `then` clause, or even into the middle of a function, without "calling" it properly. This allows for potentially very clever code that saves every last byte and cycle. It also allows for totally mind-boggling, insidious bugs in code we'd now consider plain and foolproof to write.
- theodorethomas 5y ago
  > If you have a `then` clause, you know it will only run when the `if` condition is true. Can someone please tell the clang compiler folks?
- int_19h 5y ago
  You can goto inside a conditional statement in pretty much any language I can think of that has goto. Loops are sometimes more restricted, but even then, neither C nor Pascal prohibit it (Algol-60 did, curiously), and many languages derived from them that retained goto do the same. Off the top of my head, the only mainstream language I can think of that specifically prohibits goto into inner blocks is C#.
dhosek 5y ago
Here's the actual quote, which is illuminating: “TeX was the first faily large program I had written since 1970; so it was my first nontrivial ‘structured program,’ in the sense that I wrote it while consciously applying the methodology I had learned in the early 70s from Dijkstra, Hoare, Dahl, and others. I foudn that structural programming greatly increased my confidence in the correctness of the code, while the code still existed only on paper. Therefore I could wait until the whole program was written, before trying to debug any of it. This saved lots of time, because I din't have to prepare ‘dummy’ versions of nonexistent modules while testing modules that were already written; I could test everything in its final environment.” That said, there are still 337 instances of goto in tex.web by my quick and dirty count (grep goto tex.web | grep -v '@' | wc -l), which is perhaps an undercount since there are modules that might be included multiple times thanks to how the WEB system builds its Pascal output and I don't have a Pascal reformatter to make analyzing tex.p manageable.¹ 1. The choice to "compress" the Pascal output of tangle is one of the most inexplicable choices made in the development of the TeX ecosystem.

by dhosek 5y ago

nine_k 5y ago

Often functional tests provide more bang for the buck than unit tests. Concentrating on functional tests allows to move faster. This is because most modern languages allow you to write in structural style which is impossible to get wrong without noticing. If you have a loop, you know it repeats for its condition, and does not otherwise. If you have a `then` clause, you know it will only run when the `if` condition is true. If you have a function, you know it's only computed when called. Compare it to pre-structural languages like Fortran IV or Basic, where you can freely jump into the middle of the loop, inside of what constitutes an undelimited `then` clause, or even into the middle of a function, without "calling" it properly. This allows for potentially very clever code that saves every last byte and cycle. It also allows for totally mind-boggling, insidious bugs in code we'd now consider plain and foolproof to write.

theodorethomas 5y ago
> If you have a `then` clause, you know it will only run when the `if` condition is true. Can someone please tell the clang compiler folks?
int_19h 5y ago
You can goto inside a conditional statement in pretty much any language I can think of that has goto. Loops are sometimes more restricted, but even then, neither C nor Pascal prohibit it (Algol-60 did, curiously), and many languages derived from them that retained goto do the same. Off the top of my head, the only mainstream language I can think of that specifically prohibits goto into inner blocks is C#.

dhosek 5y ago

Here's the actual quote, which is illuminating: “TeX was the first faily large program I had written since 1970; so it was my first nontrivial ‘structured program,’ in the sense that I wrote it while consciously applying the methodology I had learned in the early 70s from Dijkstra, Hoare, Dahl, and others. I foudn that structural programming greatly increased my confidence in the correctness of the code, while the code still existed only on paper. Therefore I could wait until the whole program was written, before trying to debug any of it. This saved lots of time, because I din't have to prepare ‘dummy’ versions of nonexistent modules while testing modules that were already written; I could test everything in its final environment.” That said, there are still 337 instances of goto in tex.web by my quick and dirty count (grep goto tex.web | grep -v '@' | wc -l), which is perhaps an undercount since there are modules that might be included multiple times thanks to how the WEB system builds its Pascal output and I don't have a Pascal reformatter to make analyzing tex.p manageable.¹ 1. The choice to "compress" the Pascal output of tangle is one of the most inexplicable choices made in the development of the TeX ecosystem.