simparamstr_demo.va

`include "disciplines.vams"

// Enhancement-25 demonstration: `$simparam$str(name)`.
//
// `$simparam$str` returns a *string* simulator parameter. Previously it was
// unusable: the builtin was mis-typed as returning a real, the runtime lookup
// was bugged (it walked the numeric parameter list and returned the name, not
// the value), and ngspice exposed no string parameters at all. Now it works, and
// ngspice provides:
//   * "analysis_name" -- "dc" / "ac" / "tran" / "noise" (matches analysis())
//   * "simulator"     -- "ngspice"
//
// This model reports its conductance based on the *current analysis*, read as a
// string, so a testbench can confirm the value returned in each analysis. It also
// checks the simulator name and aborts (via $error/$finish) if it is not the
// expected "ngspice" -- exercising a string `$simparam$str` in a comparison.
module simparamstr_demo(a, b);
    inout a, b;
    electrical a, b;
    parameter real g_dc   = 1.0e-3;
    parameter real g_ac   = 2.0e-3;
    parameter real g_tran = 3.0e-3;

    real g;
    string an;

    analog begin
        an = $simparam$str("analysis_name");     // string variable from $simparam$str
        if (an == "ac")        g = g_ac;
        else if (an == "tran") g = g_tran;
        else                   g = g_dc;         // "dc" (also the op / static case)
        I(a, b) <+ g * V(a, b);
    end
endmodule