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This is like the only programming language I could never learn. I just don't understand anything and I can't build any mental model of what's going on behind th

This is like the only programming language I could never learn. I just don't understand anything and I can't build any mental model of what's going on behind the hood

almostgotcaught 1y ago
it's lisp with square braces instead of parens (and then a whole bunch of other random things like a gui library in the standard library?)
- TOGoS 1y ago
  The square brackets aren't really analogous to Lisp's parentheses; REBOL / RED use parentheses for the same purpose, if you need them. The square brackets are more like square brackets in Factor or Joy; they are 'quotations' around a list of words (or other syntactic structures; basically they make a list that is not evaluated immediately).
- timbit42 1y ago
  It's actually more like Logo, which is Lisp with square brackets instead of parens and fixed arity. Sassenrath wrote Amiga Logo before starting REBOL.
TOGoS 1y ago
I wrote a paper on REBOL back in college. It is very interesting, but the syntax is definitely weird. You might think of the function call syntax as being sort of Forth-like, but with the tokens in reverse order. So like a Lisp, but without required parentheses. e.g. in the example send friend@rebol.com read http://www.cnn.com `read` knows that it takes one argument, and `send` knows that it takes two, so this ends up being grouped like (send friend@rebol.com (read http://www.cnn.com)) (which I think is valid syntax; that AST node is called a 'paren'). Weirdly, the language also has some infix operators, which seem a bit out-of-place to me. I have no idea how the 'parser'[1] works. [1] 'parsing' happens so late that it feels funny to call it that. The thing that knows how to treat an array as a representation of an evaluatable expression and evaluate it.
- deleted 1y ago
  [deleted]
- andoando 1y ago
  but why, don't get this design choice at all.
  - Izkata 1y ago
    It takes the common "function(arg1, arg2)" pattern and turns (almost) the whole language into a very simple/consistent https://en.wikipedia.org/wiki/Polish_notation https://en.wikipedia.org/wiki/Polish_notation Even things that are normally keywords and statements in other languages (like conditionals and loops) are actually just functions that conform to the exact same parsing rules.
- Izkata 1y ago
  > Weirdly, the language also has some infix operators, which seem a bit out-of-place to me. I have no idea how the 'parser'[1] works. There are no keywords or statements, only expressions. Square backets ("blocks") are used for both code and data, similar to a Lisp list. The main language (called the "'do' dialect") is entirely polish notation with a single exception for infix operators: Whenever a token is consumed, check the following token for an infix operator. If it is one, also immediately consume the immediately following one to evaluate the infix operator. This results in a few oddities / small pitfalls, but it's very consistent: * "2 + 2 * 2" = 8 because there is no order of operations, infix operators are simply evaluated as they're seen * "length? name < 10" errors (if "name" isn't a number) because the infix operator "<" is evaluated first to create the argument to "length?"
  - kazinator 1y ago
    From your brief description that is likely incomplete, it looks as if the length? function is treated as a prefix operator of low precedence relative to the infix operators. The infix operators are all at the same precedence level and have left-to-right associativity. I made an infix parser in which certain prefix operators (named math functions) have a low precedence. This allows for things like 1> log10 5 + 5 ;; i.e. log10 10 1.0 But a different prefix operator, like unary minus, binds tighter: 2> - 5 + 5 0 I invented a dynamic precedence extension to Shunting Yard which allows this parse: 3> log10 5 + 5 + log10 5 + 5 ;; i.e. (log10 5 + 5) + (log10 5 + 5) 2.0 Functions not registered with the parser are subject to a phony infix treatment if their arguments look like they might be infix and thus something similar happens to your Red example: 4> len "123" - 2 ** -: invalid operands "123" 2 "123" - 2 turns into a single argument to len, which does not participate in the infix parsing at all. log10 does participate because it is formally registered as a prefix operator. The following are also the result of the "phony infix" hack: 4> 1 cons 2 (1 . 2) 5> 1 cons 2 + 3 (1 . 5) Non-function in first place, function in second place leads to a swap: plus the arguments are analyzed for infix.
dmitrygr 1y ago
>This is like the only programming language I could never learn. Wait till you hear of Urbit and see this: https://developers.urbit.org/overview/nock https://developers.urbit.org/overview/nock
- pfych 1y ago
  I spent too long trying to learn this & hoon, not worth it ;_;
- evantbyrne 1y ago
  It's worth noting this work came from a prominent internet extremist. A generous interpretation would be that it is a high-effort troll.
  - binary132 1y ago
    It makes more sense (or helps you buy into the marketing, if you prefer) if you read the short story that Tlon took its name from.

This is like the only programming language I could never learn. I just don't understand anything and I can't build any mental model of what's going on behind the hood

almostgotcaught 1y ago

it's lisp with square braces instead of parens (and then a whole bunch of other random things like a gui library in the standard library?)

TOGoS 1y ago
The square brackets aren't really analogous to Lisp's parentheses; REBOL / RED use parentheses for the same purpose, if you need them. The square brackets are more like square brackets in Factor or Joy; they are 'quotations' around a list of words (or other syntactic structures; basically they make a list that is not evaluated immediately).
timbit42 1y ago
It's actually more like Logo, which is Lisp with square brackets instead of parens and fixed arity. Sassenrath wrote Amiga Logo before starting REBOL.

TOGoS 1y ago

I wrote a paper on REBOL back in college. It is very interesting, but the syntax is definitely weird. You might think of the function call syntax as being sort of Forth-like, but with the tokens in reverse order. So like a Lisp, but without required parentheses. e.g. in the example send friend@rebol.com read http://www.cnn.com `read` knows that it takes one argument, and `send` knows that it takes two, so this ends up being grouped like (send friend@rebol.com (read http://www.cnn.com)) (which I think is valid syntax; that AST node is called a 'paren'). Weirdly, the language also has some infix operators, which seem a bit out-of-place to me. I have no idea how the 'parser'[1] works. [1] 'parsing' happens so late that it feels funny to call it that. The thing that knows how to treat an array as a representation of an evaluatable expression and evaluate it.

deleted 1y ago
[deleted]
andoando 1y ago
but why, don't get this design choice at all.
- Izkata 1y ago
  It takes the common "function(arg1, arg2)" pattern and turns (almost) the whole language into a very simple/consistent https://en.wikipedia.org/wiki/Polish_notation https://en.wikipedia.org/wiki/Polish_notation Even things that are normally keywords and statements in other languages (like conditionals and loops) are actually just functions that conform to the exact same parsing rules.
Izkata 1y ago
> Weirdly, the language also has some infix operators, which seem a bit out-of-place to me. I have no idea how the 'parser'[1] works. There are no keywords or statements, only expressions. Square backets ("blocks") are used for both code and data, similar to a Lisp list. The main language (called the "'do' dialect") is entirely polish notation with a single exception for infix operators: Whenever a token is consumed, check the following token for an infix operator. If it is one, also immediately consume the immediately following one to evaluate the infix operator. This results in a few oddities / small pitfalls, but it's very consistent: * "2 + 2 * 2" = 8 because there is no order of operations, infix operators are simply evaluated as they're seen * "length? name < 10" errors (if "name" isn't a number) because the infix operator "<" is evaluated first to create the argument to "length?"
- kazinator 1y ago
  From your brief description that is likely incomplete, it looks as if the length? function is treated as a prefix operator of low precedence relative to the infix operators. The infix operators are all at the same precedence level and have left-to-right associativity. I made an infix parser in which certain prefix operators (named math functions) have a low precedence. This allows for things like 1> log10 5 + 5 ;; i.e. log10 10 1.0 But a different prefix operator, like unary minus, binds tighter: 2> - 5 + 5 0 I invented a dynamic precedence extension to Shunting Yard which allows this parse: 3> log10 5 + 5 + log10 5 + 5 ;; i.e. (log10 5 + 5) + (log10 5 + 5) 2.0 Functions not registered with the parser are subject to a phony infix treatment if their arguments look like they might be infix and thus something similar happens to your Red example: 4> len "123" - 2 ** -: invalid operands "123" 2 "123" - 2 turns into a single argument to len, which does not participate in the infix parsing at all. log10 does participate because it is formally registered as a prefix operator. The following are also the result of the "phony infix" hack: 4> 1 cons 2 (1 . 2) 5> 1 cons 2 + 3 (1 . 5) Non-function in first place, function in second place leads to a swap: plus the arguments are analyzed for infix.

dmitrygr 1y ago

>This is like the only programming language I could never learn. Wait till you hear of Urbit and see this: https://developers.urbit.org/overview/nock https://developers.urbit.org/overview/nock

pfych 1y ago
I spent too long trying to learn this & hoon, not worth it ;_;
evantbyrne 1y ago
It's worth noting this work came from a prominent internet extremist. A generous interpretation would be that it is a high-effort troll.
- binary132 1y ago
  It makes more sense (or helps you buy into the marketing, if you prefer) if you read the short story that Tlon took its name from.