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)
And the problematic code switches to
concat "I want "
getwish from me
. " - " username
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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