On Friday, 1 May 2015 at 03:34:53 UTC, Luigi wrote:
Hi everybody.
I am tring to use a function where its parameter is another
function, and at the same time are both already made - they
cannot be modified - and the second one has to be conditioned
before to be passed as argument.
Let's say I have these function and I cannot modify:
-jac(+d) that works on function and return real
real jac(real function(real) fun, real x) {return d(fun, x);}
real d(real function(real) fun, real x) {return fun(x);}
-F1 that works on two reals and return real
real F1(real a, real b) {return a + b;}
So I need a way to condition F1 fixing b and then pass it to
jac as argument.
To do that I've created a delegate 'simp' conditionig F1:
real delegate(real) simp(real function(real, real) f, real x) {
real _simp(real z) {
return f(z, x);
}
return &_simp;
}
(here 'simp' fixes b at x).
My main is:
void main() {
real x_n = 1;
real x_m = -1;
real delegate(real) s_n = simp(&F1, x_n);
//auto J = jac(s_n, x_m); //Error: function app.jac (real
function(real) fun, real x) is not callable using argument
types (real delegate(real), real)
}
the code fails because jac expect as argument a function but I
found only a delegate to obtain a simplified function without
any touch at already made functions jac, d and F1.
There is a clean way to make it possible? I mean: without to
touch (neither rewrite) jac, d and F1, obtain simplied F1 to
pass to jac.
If x_n is a constant (enum), you can use that to create a
function instead of a delegate:
----
void main() {
enum real x_n = 1;
real x_m = -1;
real function(real) s_n = z => F1(z, x_n);
auto J = jac(s_n, x_m);
}
----
If x_n is not constant, then the only way I see to make this
work, is to use a module variable:
----
real x_n;
void main() {
x_n = 1;
real x_m = -1;
real function(real) s_n = z => F1(z, x_n);
auto J = jac(s_n, x_m);
}
----
