5 ms·

Pyret inherits hyphens-in-identifiers from Scheme/Racket. One of Pyret's largest users, Bootstrap [1], has long-used a dialect of Scheme, and has recently intro

by jswrenn 10y ago

Pyret inherits hyphens-in-identifiers from Scheme/Racket. One of Pyret's largest users, Bootstrap [1], has long-used a dialect of Scheme, and has recently introduced a curriculum that uses Pyret. For these users, "virtually every other language" allows for hyphens in identifiers. Scheme mitigates the spacing issue with s-expressions. Pyret attempts to mitigate it by enforcing that operators should be separated from their operand with at least one space. (Disclosure: I am an occasional developer of Pyret.) [1] http://www.bootstrapworld.org/ http://www.bootstrapworld.org/

eridius 10y ago
Scheme and Racket are both LISPs, with very different syntax. Hyphens in identifiers aren't a hazard, because binary operators don't go between two other identifiers, and operators must be separated with spaces, e.g. subtraction looks like `(- 2 1)` instead of `2 - 1`. This means that using hyphens in identifiers is quite safe. But Pyret is using more traditional syntax, where binary operators go between their operands, e.g. `2 - 1`, which means using hyphens in identifiers is a hazard as the parent comment describes.
- simplify 10y ago
  The problem is overblown. It's not going to cause any deep, hard-to-debug errors. If you accidentally type `a-b`, you'll get an error message that says "a-b is not defined". Fix it and you're done.
  - samcal 10y ago
    While I agree that the problem is not a very big deal, I think that you might be surprised how difficult understanding compiler errors can be for newcomers.
    - CodeMage 10y ago
      I regard that as a valuable teaching moment: "This, kids, is a great example of what you'll have to deal with all the time. Computers are not smart and neither are compilers. Forget a semicolon or some whitespace, and it's your job to clean up the mess after your compiler shits its bed."
      - dkersten 10y ago
        Having been a tutor of first-year beginner programming students many years ago, my experience has been that its not quite as simple as this. The number of people who forgot even the most simple syntax rules towards the end of the semester, even after having shown them during each lab session, was surprisingly high. You tell them that the computer is super dumb and pedantic and they understand this. So you tell them the rules (semi colon at the end of line perhaps) and they understand. Then an hour later and they're staring blankly at the screen wondering why they got the exact same error again. Obviously not all students are like this and almost all did get it after a while, but you'll be repeating your statement to them enough times that you wished the language didn't have whatever warts is causing the confusion. I found Java particularly bad, because you have to tell beginners to ignore 90% of the hello world program (class ... public static void main ... - you have to tell them "hey, ignore class, public, static, void etc for now, we will cover it later"), which isn't satisfying at all and in my experience caused more confusion still... Yes, you've got to treat it as a learning experience, but the students usually see it as a roadblock and cause of frustration. Often one that doesn't make sense to them and they question why its even a thing. ("why can I use '_' in identifiers and not '-'?", not too hard to explain of course but its yet another bit of incidental complexity to them)
    - skrishnamurthi 10y ago
      The Pyret design team has done perhaps the most in-depth research into error messages of anyone [e.g.: http://cs.brown.edu/~sk/Publications/Papers/Published/mfk-measur-effect-error-msg-novice-sigcse/ http://cs.brown.edu/~sk/Publications/Papers/Published/mfk-me..., http://cs.brown.edu/~sk/Publications/Papers/Published/mfk-mind-lang-novice-inter-error-msg/ http://cs.brown.edu/~sk/Publications/Papers/Published/mfk-mi...]. We're deeply aware of the effect of error messages. This isn't a problem.
spacemanmatt 10y ago
I don't recall having real trouble with category errors like this as a beginner. Do you think that is a serious problem?

by jswrenn 10y ago

eridius 10y ago

Scheme and Racket are both LISPs, with very different syntax. Hyphens in identifiers aren't a hazard, because binary operators don't go between two other identifiers, and operators must be separated with spaces, e.g. subtraction looks like `(- 2 1)` instead of `2 - 1`. This means that using hyphens in identifiers is quite safe. But Pyret is using more traditional syntax, where binary operators go between their operands, e.g. `2 - 1`, which means using hyphens in identifiers is a hazard as the parent comment describes.

simplify 10y ago
The problem is overblown. It's not going to cause any deep, hard-to-debug errors. If you accidentally type `a-b`, you'll get an error message that says "a-b is not defined". Fix it and you're done.
- samcal 10y ago
  While I agree that the problem is not a very big deal, I think that you might be surprised how difficult understanding compiler errors can be for newcomers.
  - CodeMage 10y ago
    I regard that as a valuable teaching moment: "This, kids, is a great example of what you'll have to deal with all the time. Computers are not smart and neither are compilers. Forget a semicolon or some whitespace, and it's your job to clean up the mess after your compiler shits its bed."
    - dkersten 10y ago
      Having been a tutor of first-year beginner programming students many years ago, my experience has been that its not quite as simple as this. The number of people who forgot even the most simple syntax rules towards the end of the semester, even after having shown them during each lab session, was surprisingly high. You tell them that the computer is super dumb and pedantic and they understand this. So you tell them the rules (semi colon at the end of line perhaps) and they understand. Then an hour later and they're staring blankly at the screen wondering why they got the exact same error again. Obviously not all students are like this and almost all did get it after a while, but you'll be repeating your statement to them enough times that you wished the language didn't have whatever warts is causing the confusion. I found Java particularly bad, because you have to tell beginners to ignore 90% of the hello world program (class ... public static void main ... - you have to tell them "hey, ignore class, public, static, void etc for now, we will cover it later"), which isn't satisfying at all and in my experience caused more confusion still... Yes, you've got to treat it as a learning experience, but the students usually see it as a roadblock and cause of frustration. Often one that doesn't make sense to them and they question why its even a thing. ("why can I use '_' in identifiers and not '-'?", not too hard to explain of course but its yet another bit of incidental complexity to them)
  - skrishnamurthi 10y ago
    The Pyret design team has done perhaps the most in-depth research into error messages of anyone [e.g.: http://cs.brown.edu/~sk/Publications/Papers/Published/mfk-measur-effect-error-msg-novice-sigcse/ http://cs.brown.edu/~sk/Publications/Papers/Published/mfk-me..., http://cs.brown.edu/~sk/Publications/Papers/Published/mfk-mind-lang-novice-inter-error-msg/ http://cs.brown.edu/~sk/Publications/Papers/Published/mfk-mi...]. We're deeply aware of the effect of error messages. This isn't a problem.

spacemanmatt 10y ago

I don't recall having real trouble with category errors like this as a beginner. Do you think that is a serious problem?