On Sat, Feb 9, 2013 at 7:47 AM, Arne Babenhauserheide <[email protected]> wrote:
> Hi,
>
> You might have noticed that after initial excitement I drew back from
> readable again. The reasons were partly time problems, but mostly that I have
> the feeling that readable currently moves into a direction which does not
> feel right to me.
>
> There is now indentation based syntax (great!) with special casing for
> sublists (useful for nested functions), restart lists (hm) and now <* ... *>
> (looks alien).
>
>
> To me this lost the beauty of lisp, that you have few fixed syntax rules
> which become second nature. Instead we now have mixed metaphors and code
> which can be written in a multitude of ways - which goes counter to
> readability (it’s not about every special case being beautiful, but having a
> consistent style which is nicely readable in most cases).
>
>
> And it just felt wrong to see more and more special cases being added. That
> smelled of a problem in the basic concept.
>
>
> Also I wondered how code like the following would be represented:
>
> (concat "I want " (getwish from me) " - " username)
>
> Currently I only see this option:
>
> concat "I want " getwish(from me) " - " username
>
> But not this
>
> concat "I want "
> getwish from me
> " - " username
>
>
> I did not get my mind off the idea, though (and did not want to), and I
> derived a simpler concept from it:
>
> - if a line starts with a . it is a continuation of the parent line
> (the last line which had lower indentation).
> - if a line is further indented than the previous line,
> it opens a new bracket (except if it starts with a .),
> - if it is indented equally, then it closes a bracket and opens a new one
> (except if it starts with a ., then it only closes a bracket).
> - A : sourrounded by whitespace defines a new indentation level
> (similar to restart list, but more general).
>
> That provides 4 clear rules, one of which is similar to an existing rule
> ( “(. a) → a” becomes “(. a b c) → a b c” ). And that’s all the syntax to
> learn with no special cases.
>
>
> Essentially all it does is giving up the rule that a variable on its own is a
> variable instead of a function call.
>
>
> By prefixing all variables with “.”, it also gets line continuations for free:
>
> a b c d e
> . f g h
> . i j k
>
> is equivalent to
>
> (a b c d e
> f g h
> i j k)
>
Really? Because your rule is:
> - if it is indented equally, then it closes a bracket and opens a new one
> (except if it starts with a ., then it only closes a bracket).
So:
(a b c d e
f g h
) i j k
?
>
> And the problematic code switches to
>
>
> concat "I want "
> getwish from me
> . " - " username
You know, this second example suggests that maybe the "then it only
closes the bracket" is incorrect.
Here's a set that seems to be closer to what you want (ignoring ":" for now)
- at the start of the read, the "previous line's indent" is considered
as negative.
- A line with the same indent as the previous line inserts a ")". It
also inserts a "(" unless the line starts with "."
- a line with a greater indent than the previous line inserts a "("
unless the line starts with "."
- a line with a lesser indent than the previous line inserts a ")" for
each indentation level popped, followed by a closing ")"
- "." at the start of the line is removed.
So:
concat "I want"
getwish from me
. " - " username
at the start of read, the previous line's indent is negative, so
"concat" at indent 0 is more indented and inserts a "(":
(concat "I want"
^
getwish from me
. " - " username
the next line is more indented than the previous line, so insert:
(concat "I want"
(getwish from me
^
. " - " username
The next line has same indent, but also a ".", so insert only a ")":
(concat "I want"
(getwish from me
) " - " username
^
The next line is empty, which is an indent at 0, so pop off one indent
(one ")") and add a closing ):
(concat "I want"
(getwish from me
) " - " username
))
erk, that has an extra ")",
... or something anyway. Maybe "." should raise a flag that
suppresses ")" for the next line. But I think that ends up having a
stack in the case of indentation.
...or something, at least. Hehe.
>
>
> Some of the Examples¹ from the sf.net site look like this (also using curly
> infix, since that’s useful for easier math):
>
>
> define : fibfast n
> if {n < 2}
> . n
> fibup n 2 1 0
>
> define : fibup maxnum count n-1 n-2
> if {maxnum = count}
> {n-1 + n-2}
> fibup maxnum {count + 1} {n-1 + n-2} n-1
>
> define : factorial n
> if {n <= 1}
> . 1
> {n * factorial{n - 1}}
>
> define : gcd x y
> if {y = 0}
> . x
> gcd y : rem x y
>
>
>
> define : add-if-all-numbers lst
> call/cc
> lambda : exit
> let loop
> :
> lst lst
> sum 0
> if : null? lst
> . sum
> if : not : number? : car lst
> exit #f)
> + : car lst
> loop : cdr lst
>
>
>
> I wrote this to question if all those special cases (\\, $, <*…*>) are really
> the sign of an elegant solution - or not rather the hairy bits grown by
> limitations of the base design.
>
> And to ask you to have a look at the simpler proposal and see whether I
> overlooked some problems.
>
> I wrote it now (late at night) even though the idea has spooked my mind for
> the past few weeks, because I saw the idea to go SRFI now, so I feared that
> the limited base design (IMHO) could become set in stone and limit all
> further work which could be done to make lisp more readable.
>
> Best wishes,
> Arne
>
> ¹: http://sourceforge.net/p/readable/wiki/Examples/
>
> --
> Ein Würfel System - einfach saubere Regeln:
>
> - http://1w6.org
>
>
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