Hi Yann,
Trying to understand what you wrote, I did:
process = x letrec { 'x = y+10;
y = x-1; };
and tried to look at the block diagram.
The compiler (revision 6d112cfa73820c2d0080a76a1efb8499001019a8) gives
me:
test.dsp:2:syntax error, unexpected IDENT, expecting DELAY1 or RBRAQ
What's going on?
Cheers,
Bart.
On Tue, Jun 21, 2016 at 07:01:09PM +0200, Yann Orlarey wrote:
>We have pushed on the master branch an experimental extension to Faust: the
>`letrec{...}` construction. It is somehow similar to `with{...}`, but for
>_difference equations_ instead of regular definitions. It allows to easily
>express groups of mutually recursive signals, for example `x(t)` such that:
>
>x(t) = y(t-1)+10;
>y(t) = x(t-1)-1;
>
>as:
>
>x letrec { 'x = y+10;
>'y = x-1; }
>
>Please remark the special notation `'x=y+10` instead of `x=y'+10`. Here
>`'x` represents the _next value_ of `x` defined according of the _current
>value_ of `y`. It makes syntactically impossible to write non-sensical
>equations like `x=x+1`.
>
>Here is a more involved example. Let say we want to define an envelop
>generator with an attack time, a release time and a gate signal. A possible
>definition is the following:
>
>ar(a,r,g) = v letrec {
> 'n = (n+1) * (g<=g');
> 'v = max(0, v + (n<a)/a - (n>=a)/r) * (g<=g');
> };
>
>With the following semantics for `n(t)` and `v(t)`:
>
>n(t) = (n(t-1)+1) * (g(t) <= g(t-1))
>v(t) = max(0, v(t-1)+(n(t-1)<a(t))/a(t)-(n(t-1)>=a(t))/r(t) )
> * (g(t)<=g(t-1))
>
>Tests and comments are welcome.
>
>Cheers
>
>Yann
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