The phrase "considered harmful" has become a meme and is the go-to phrase (pun intended) for essayists looking to criticise some aspect of computing
https://www.cs.utexas.edu/users/EWD/transcriptions/EWD12xx/E... "I must confess that I was very slow on appreciating LISP’s merits. My first introduction was via a paper that defined the semantics of LISP in terms of LISP, I did not see how that could make sense, I rejected the paper and LISP with it."
For example in a language without GOTO inside an if statement the guarding condition is known to be a predicate (at least until another operation changes it) whereas in a language with unrestricted GOTO there is no guarantee whatsoever that the guard holds since execution could have jumped past it.
"At the I F I P Congress in 1971 I had the pleasure of meeting Dr. Eiichi Goto of Japan, who cheerfully complained that he was always being eliminated."
"For many years, the go to statement has been troublesome in the definition of correctness proofs and language semantics....Just recently, however, Hoare has shown that there is, in fact, a rather simple way to give an axiomatic definition of go to statements; indeed, he wishes quite frankly that it hadn't been quite so simple."
I cannot find anything written by Hoare about it, but Knuth goes on to describe it: the idea is that labels have associated preconditions and GOTOs have the semantics { precondition(L) } goto L { false }.
"Informally, a(L) [my "precondition(L)"] represents the desired state of affairs at label L; this definition says essentially that a program is correct if a(L) holds at L and before all "go to L" statements, and that control never "falls through" a go to statement to the following text. Stating the assertions a(L) is analogous to formulating loop invariants. Thus, it is not difficult to deal formally with tortuous program structure if it turns out to be necessary; all we need to know is the "meaning" of each label."
It is a very nice paper. Some sources:
http://www.kohala.com/start/papers.others/knuth.dec74.html
Thanks for sharing that paper! As an aside, it's really remarkable just how readable the state of the art papers such as the one you shared there from that era are. Either computing science has greatly advanced to the point where clarity is no longer achievable without years of specialized preparatory study or the quality of writing has regressed.