Re: scheme with Frescobaldi

[Freeman Gilmore]

​

On Mon, Jun 25, 2018 at 9:02 PM, Aaron Hill <address@hidden> wrote:

On 2018-06-25 17:25, Freeman Gilmore wrote:

On Mon, Jun 25, 2018 at 9:29 AM, Urs Liska <address@hidden> wrote:

Try this file:

\version "2.19.80"

#(let
  ((something 'something-else))
  (display something)
  (newline)
  (display something)(display something))

In you first example #(let...) what function does 'let' preform?

Here is the reference on `let` for Guile:

https://www.gnu.org/software/guile/manual/html_node/Local-Bindings.html#Local-Bindings

Without repeating verbatim what is there, `let` is a way of defining locally-scoped variables.

In the example above, `something` is being defined as `'something-else`, and it is being referenced later in the function body several times.  But as a local variable, `something` is ephemeral and will no longer be valid outside of the scope of the let-block body.  Consider:

%%%%
  #(let
    ((a 1) (b 2))
    (display (+ a b))    #! should output 3 !#
    (let
     ((a b) (c 3))
     (display (+ a c))   #! should output 5 !#
    )
    (display a)          #! should output 1 !#
    #!(display c)!#      #! error: unbound variable c !#
   )
%%%%

The inner let here redefines `a` while also defining `c`.  Outside of its body, the original value of `a` is effectively restored but then `c` is no longer bound so you cannot refer to it.

Hope that helps,

-- Aaron Hill

 

​Thanks Aaron​:

​The example was very clear. Now I am reading the reference next.

Thank you, ƒg

_______________________________________________
lilypond-user mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/lilypond-user