Re: scheme with Frescobaldi

[Aaron Hill]

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