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I've used rationals by default in Racket/Scheme for literally 3+ decades now. It's fine. Dart is trying to be an industrial-strength language. We're trying to c

I've used rationals by default in Racket/Scheme for literally 3+ decades now. It's fine. Dart is trying to be an industrial-strength language. We're trying to create an awesome initial programming experience. To the beginner, those denominators are nowhere near as much of a problem as "numbers" that don't make sense. But we draw limits. Did you try the `sin(pi / 6)` example? You'll find that Pyret produces a rather interesting result that is also instructive. (Hint: it will produce neither true nor false.)

IshKebab 5y ago
I'm a bit dubious that magic stuff like this really makes anything easier. It's like JavaScript's truthiness and type coersion. It's trying to be friendly and work most of the time, but in reality it is more complex because now you have to remember a whole set of rules about how exactly the magic behaves.
- justinpombrio 5y ago
  Waaaay less magic than Javascript. Looks like the rules are described here. Two kinds of numbers: exact and rough. Unless you use trig functions it will all be exact. https://www.pyret.org/docs/latest/numbers.html https://www.pyret.org/docs/latest/numbers.html Fun fact about Javascript: there are string and number constants x, y, and z, such that `x < y` and `y < z` and `z < x`. No NaN shenanigans, just regular small strings and numbers. Hint: it involves a string containing digits that starts with "0", thus sometimes getting implicitly coerced to octal. Think about what this means for sorting!
- epidemian 5y ago
  My guess is that you didn't try @skrishnamurthi suggestion: > Did you try the `sin(pi / 6)` example? You'll find that Pyret produces a rather interesting result that is also instructive. The result of this doesn't feel like magic and doesn't resemble "JavaScript's truthiness and type coersion" at all IMO. Here's a live code editor where you can try it out: https://code.pyret.org/editor https://code.pyret.org/editor I found it to be a very refreshing and intuitively-guiding experience :) --- Spoiler alert! So, fist i had to find how to access pi and sin(), which was simple enough googling for documentation. Typing `num-sin(PI / 6)` on he editor already gives an interesting result: ~0.49999999999999994 That ~ there looks suspicious! Then i tried `num-sin(PI / 6) == 1 / 2`, which seems to be syntactically invalid and yields an awesome error message: Reading this expression errored: num-sin(PI / 6) == 1 / 2 The == and / operations are at the same grouping level. Add parentheses to group the operations, and make the order of operations clear. Kudos to the Pyret team for such a nice error message! So finally, adding those missing parens, `num-sin(PI / 6) == (1 / 2)`, yields another informative and useful error message: Attempted to compare a Roughnum to an Exactnum for equality, which is not allowed: The left side was: ~0.49999999999999994 The right side was: 0.5 Consider using the within function to compare them instead. All in all, i'm very impressed with the clarity and approachability of the language. Thanks @skrishnamurthi for the suggestion of trying this out! :D
  - kazinator 5y ago
    What's the point of an infix syntax that demands obvious. unnnecessary parentheses, as a matter of correctness? "grouping level" is a cringe-inducing dumbing down of proper terminology. It suggests associativity, but associativity does not have levels. It must be referring to "precedence". = and / are not at the same level of precedence in basic mathematics! In elementary school you learn y = x / 2 without requiring parentheses. It makes sense to require parentheses when exotic, unfamiliar operators are involved for which the precedence and associativity would be hard to remember. Not for operators drilled into your head by sixth grade.

IshKebab 5y ago

I'm a bit dubious that magic stuff like this really makes anything easier. It's like JavaScript's truthiness and type coersion. It's trying to be friendly and work most of the time, but in reality it is more complex because now you have to remember a whole set of rules about how exactly the magic behaves.

justinpombrio 5y ago
Waaaay less magic than Javascript. Looks like the rules are described here. Two kinds of numbers: exact and rough. Unless you use trig functions it will all be exact. https://www.pyret.org/docs/latest/numbers.html https://www.pyret.org/docs/latest/numbers.html Fun fact about Javascript: there are string and number constants x, y, and z, such that `x < y` and `y < z` and `z < x`. No NaN shenanigans, just regular small strings and numbers. Hint: it involves a string containing digits that starts with "0", thus sometimes getting implicitly coerced to octal. Think about what this means for sorting!
epidemian 5y ago
My guess is that you didn't try @skrishnamurthi suggestion: > Did you try the `sin(pi / 6)` example? You'll find that Pyret produces a rather interesting result that is also instructive. The result of this doesn't feel like magic and doesn't resemble "JavaScript's truthiness and type coersion" at all IMO. Here's a live code editor where you can try it out: https://code.pyret.org/editor https://code.pyret.org/editor I found it to be a very refreshing and intuitively-guiding experience :) --- Spoiler alert! So, fist i had to find how to access pi and sin(), which was simple enough googling for documentation. Typing `num-sin(PI / 6)` on he editor already gives an interesting result: ~0.49999999999999994 That ~ there looks suspicious! Then i tried `num-sin(PI / 6) == 1 / 2`, which seems to be syntactically invalid and yields an awesome error message: Reading this expression errored: num-sin(PI / 6) == 1 / 2 The == and / operations are at the same grouping level. Add parentheses to group the operations, and make the order of operations clear. Kudos to the Pyret team for such a nice error message! So finally, adding those missing parens, `num-sin(PI / 6) == (1 / 2)`, yields another informative and useful error message: Attempted to compare a Roughnum to an Exactnum for equality, which is not allowed: The left side was: ~0.49999999999999994 The right side was: 0.5 Consider using the within function to compare them instead. All in all, i'm very impressed with the clarity and approachability of the language. Thanks @skrishnamurthi for the suggestion of trying this out! :D
- kazinator 5y ago
  What's the point of an infix syntax that demands obvious. unnnecessary parentheses, as a matter of correctness? "grouping level" is a cringe-inducing dumbing down of proper terminology. It suggests associativity, but associativity does not have levels. It must be referring to "precedence". = and / are not at the same level of precedence in basic mathematics! In elementary school you learn y = x / 2 without requiring parentheses. It makes sense to require parentheses when exotic, unfamiliar operators are involved for which the precedence and associativity would be hard to remember. Not for operators drilled into your head by sixth grade.