Re: "Structure and interpretation" of Scheme (was: Comments wanted on code highlighting in PDF output)

[Luca Fascione]

Thanks Jean, this is very useful and informative.
I'll go read sicp (again, last time was several years ago) and meanwhile
experiment with the code you sent me.

As to format, it's not that I don't get it, it's just that straight up
interpolation, being more compact, is better for simple things.
In Scheme you do sprintf, that's ok. It's very cool for the bigger things
and I certainly prefer it to C++ streams (in C++ I mean).
But there too, for complex types being able to overload << is real handy,
and if we only had printf() it'd be less fun.

I'll go read, might come back with questions,
very very grateful in the meantime.

One question back to lilypond:
as I was saying I theorize it ought to be the fingering to "push up" (in
\stemsUp mode) the beaming,
can I fiddle around and mess with the stem lengths in before-line-break (or
after-line-break)?

Thanks again
Luca

On Mon, Feb 21, 2022 at 10:34 PM Jean Abou Samra <jean@abou-samra.fr> wrote:

>
>
> Le 21/02/2022 à 22:19, Luca Fascione a écrit :
> >
> >
> > On Mon, Feb 21, 2022 at 9:58 PM Jean Abou Samra <jean@abou-samra.fr>
> > wrote:
> >
> >     Not sure what confuses you?
> >
> >
> > In TCL I got used to bare strings being values, not varnames, so I'm
> > learning stuff again.
> > It's just different, but in languages that in many other things are
> > very similar.
> > Of course I don't find it confusing in C or python...
> > But I was just reading the page you suggested: as a beginner I read
> > this example
> >   (define
> > <
> http://www.schemers.org/Documents/Standards/R5RS/HTML/r5rs-Z-H-8.html#%_idx_190>
>
> > capital-cities '
> > <
> http://www.schemers.org/Documents/Standards/R5RS/HTML/r5rs-Z-H-7.html#%_idx_88>((sweden
>
> > . stockholm) (usa . washington) (germany . berlin) ))
> >
> > As an associative array, where the values are dereferenced variables,
> > but I don't know about the keys, whether they're strings, symbols or
> > also variables.
>
>
>
> No, the values are also symbols, not dereferenced variables.
>
> $ guile
> GNU Guile 3.0.5.130-5a1e7
> Copyright (C) 1995-2021 Free Software Foundation, Inc.
>
> Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
> This program is free software, and you are welcome to redistribute it
> under certain conditions; type `,show c' for details.
>
> Enter `,help' for help.
> scheme@(guile-user)>  (define capital-cities
>                         '((sweden . stockholm)
>                           (usa . washington)
>                           (germany . berlin)
>                          ))
> scheme@(guile-user)> capital-cities
> $1 = ((sweden . stockholm) (usa . washington) (germany . berlin))
>
>
> 'blabla is equivalent to (quote blabla) which prevents
> evaluation inside blabla. When a symbol appears in code,
> it dereferences a variable, unless it's inside a quote
> in which case you get it as a symbol.
>
>
> > Say the first line, if it was python, would it be
> > capitalcities["sweden"] = stockholm
> > or
> > capitalcities[sweden] = stockholm
> > or
> > capitalcities['sweden'] = stockholm  # fake out a symbol with ticks,
> > just for argument's sake
>
> capitalcities['sweden'] = 'stockholm'
>
>
> > The TCL form uses parens for array keys, the setter would be
> >
> > set capital-cities(sweden) $stockholm
> >
> > Note this is exactly equivalent to these two:
> >
> > set capital-cities("sweden") $stockholm
> > set capital-cities({sweden}) $stockholm
> >
> > dblquotes interpolate (like in shell/perl) and curlies don't (like
> > ticks in shell/perl).
> >
> > It's easier to keep one's head straight given there's so little extra
> > typing to guide you while one is still learning.
>
>
> I know nothing about Tcl, but in Scheme there is no
> difference between dereferencing a variable and dereferencing
> a "command". An unquoted symbol that happens to be evaluated
> deferences a variable, that's all. In this sense, I guess
> you could think of it as if your Tcl code read
>
> $set capital-cities("sweden") $stockholm
>
> with $ in front of set, because set! is really a variable
> that has a value in the same namespace as any other variable
> (OK, it won't work if you write it as-is in Guile >= 2 due
> to the way that has evolved, but set! still has a value
> you can retrieve with (module-ref (current-module) 'set!) .)
>
> Yes, I know, (set! x ...) does not evaluate x, but this
> is because set! is a special macro that does special
> things with its arguments. In other words, Scheme thinks
> differently from Tcl in that in Tcl you always have the
> $x syntax to dereference a variable, whereas in Scheme
> the interpretation of a symbol is always subject to
> what the surrounding context wants to do with it.
> The default is to dereference a symbol. Unless quoted,
> or under set!, or define, or such.
>
>
> > I'll learn, I'm just not there yet.
> >
> >     It's the same as in most
> >     other languages (such as C++): a bare name dereferences
> >     a variable. The exception to this is within quotes,
> >     which prevent evaluation of symbols, returning them naked.
> >
> >
> > That too, interpolating into strings, like you have in TCL/perl/shell
> > ("Hello $username" kinda stuff) is handy :-)
>
>
> (format #t "Hello ~a" username)
>
> ?
>
>
>
>