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Nit: Many Pascal compilers / runtimes extended the language in non-standard ways, including various schemes for storing string length in front of the string. B

Nit: Many Pascal compilers / runtimes extended the language in non-standard ways, including various schemes for storing string length in front of the string. But nothing like this was ever part of the ISO Pascal standard, and it was certainly not in the "PASCAL User Manual and Report" by Kathleen Jensen and Niklaus Wirth. In fact, in standard Pascal, string handling is extremely rudimentary; there was no way to express "this variable / parameter / pointer refers to a string with a length not known at compile-time".

pjmlp 4y ago
They were on the ISO Extended Pascal, which hardly mattered because by then, USCD Pascal and Object Pascal already had taken over the world of Pascal dialects, both of which had better ways to deal with strings. https://www.iso.org/standard/18237.html https://www.iso.org/standard/18237.html Additionally, Modula-2 was already available in 1978, sorting out all the issues of original Pascal, with all the features needed for a safe systems programming language in the late 70's.
- drfuchs 4y ago
  In the late 70’s, there were production-quality Pascal compilers for DEC 20 / ITS / SAIL, Vax/VMS, IBM 360/370, together covering much of academic computing and most of the ARPAnet. Even consulting Wirth, Knuth couldn’t find suitable Modula-2 compilers available for these, so TeX used Pascal and not Modula-2. Near as we heard, it was only ever seriously used on the niche ETH workstation?
  - pjmlp 4y ago
    That is like complaining that C wasn't available in plenty of computer hardware outside Bell Labs until early 1980's, after UNIX V6 release, was it ever seriously used outside AT&T research units? Do you seriously expect in two years left of 70's for Modula-2 to be available everywhere?
    - drfuchs 4y ago
      No, I was simply responding to your statement that "Modula-2 was already available in 1978". This phrasing might give the wrong impression; Modula-2's practical availability was extremely limited. No doubt it was a fine language, but it never caught on to anywhere near the extent Pascal had, before C proceeded to take over the world. If you wanted to write run-everywhere software, Modula-2 was never a tenable choice. But we digress. The topic at hand was "How does Pascal store strings?" I stand by the pedantic statement that ISO Standard Pascal does not require string lengths to be stored with the string (nor anywhere else); there's no way for the programmer to obtain the length of a string at compile-time, never mind run-time, without resorting to some sort of compiler-specific language extension (most (all?) of which did indeed put the string length in front). Conversely, the Extended Pascal standard pretty much requires strings to instead be implemented as "fat pointers," consisting of a length and a pointer to the actual characters. I say this because substring operations return references to pieces of the original string, thus you can't stuff a length in front of the actual characters of the substring, as this would over-write characters in the original string.

pjmlp 4y ago

They were on the ISO Extended Pascal, which hardly mattered because by then, USCD Pascal and Object Pascal already had taken over the world of Pascal dialects, both of which had better ways to deal with strings. https://www.iso.org/standard/18237.html https://www.iso.org/standard/18237.html Additionally, Modula-2 was already available in 1978, sorting out all the issues of original Pascal, with all the features needed for a safe systems programming language in the late 70's.

drfuchs 4y ago
In the late 70’s, there were production-quality Pascal compilers for DEC 20 / ITS / SAIL, Vax/VMS, IBM 360/370, together covering much of academic computing and most of the ARPAnet. Even consulting Wirth, Knuth couldn’t find suitable Modula-2 compilers available for these, so TeX used Pascal and not Modula-2. Near as we heard, it was only ever seriously used on the niche ETH workstation?
- pjmlp 4y ago
  That is like complaining that C wasn't available in plenty of computer hardware outside Bell Labs until early 1980's, after UNIX V6 release, was it ever seriously used outside AT&T research units? Do you seriously expect in two years left of 70's for Modula-2 to be available everywhere?
  - drfuchs 4y ago
    No, I was simply responding to your statement that "Modula-2 was already available in 1978". This phrasing might give the wrong impression; Modula-2's practical availability was extremely limited. No doubt it was a fine language, but it never caught on to anywhere near the extent Pascal had, before C proceeded to take over the world. If you wanted to write run-everywhere software, Modula-2 was never a tenable choice. But we digress. The topic at hand was "How does Pascal store strings?" I stand by the pedantic statement that ISO Standard Pascal does not require string lengths to be stored with the string (nor anywhere else); there's no way for the programmer to obtain the length of a string at compile-time, never mind run-time, without resorting to some sort of compiler-specific language extension (most (all?) of which did indeed put the string length in front). Conversely, the Extended Pascal standard pretty much requires strings to instead be implemented as "fat pointers," consisting of a length and a pointer to the actual characters. I say this because substring operations return references to pieces of the original string, thus you can't stuff a length in front of the actual characters of the substring, as this would over-write characters in the original string.