arrayret_examples

arrayret_examples — array return values from analog functions (Enhancement-23)

Demonstrates array return values from analog functions, using version11's own openvaf-r and ngspice-46. This completes the array-in-functions arc:

• Enhancement-18 — array arguments (input, by value)
• Enhancement-20 — array output/inout arguments (write-back)
• Enhancement-23 — array return values ← this folder

Syntax

analog function real[0:n] f;   // return type carries array dimensions
    ...
    f[i] = ...;                // the body writes the return array's elements
endfunction
...
real c[0:n];
c = f(args);                   // the whole returned array is copied into c

arrayret_demo.va implements a cubic polynomial device I = c0 + c1·V + c2·V² + c3·V³ two ways:

• polyret — a function powers(x) returns the array {1, x, x², x³}, summed with the coefficients at the call site;
• polyret_arg — the returned array is fed straight into an array-argument function (E-18), composing an array return with an array argument in one expression.

Run

python3 verify_arrayret.py

Expected (ALL PASS): for both modules and across a bias sweep, the DC current matches the closed-form polynomial (~1e-9) and the AC conductance matches the exact derivative gm = c1 + 2·c2·V + 3·c3·V² (~1e-9) — i.e. the autodiff Jacobian flows through the array return.

Notes / limitations

• An array-returning function call is only valid as the whole right-hand side of an array assignment (c = f(...)); it can't be used as a sub-expression.
• The destination must be a writable array variable of the same length as the return array; a length mismatch is a compile-time type error.
• The return array's element variables are function-local (written by the body, then copied into the caller's array), so the derivative flows through exactly as for array arguments (E-18) and output arguments (E-20).