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simparamstr_examples — $simparam$str(name) (Enhancement-25)

Demonstrates $simparam$str(name), which returns a string simulator parameter, using version11's own openvaf-r and ngspice-46. Previously it was unusable — three separate defects: the builtin was mis-typed as returning a real, the runtime lookup was bugged (it walked the numeric parameter list and returned the name instead of the value), and ngspice exposed no string parameters at all.

What it does now

ngspice provides two string simulator parameters:

  • "analysis_name" — "dc" / "ac" / "tran" / "noise" (same naming as the analysis() function), derived from the current analysis mode;
  • "simulator" — "ngspice".

They can be read into a string variable, compared, and used to branch on the current analysis, e.g.:

string an;
an = $simparam$str("analysis_name");
if (an == "tran") ... else ...

The model

simparamstr_demo.va sets its conductance from $simparam$str("analysis_name"): g_dc in dc/op, g_ac in ac, g_tran in tran.

Run

python3 verify_simparamstr.py

Expected (ALL PASS): running each analysis and checking the terminal current confirms the correct string is returned in dc, ac, and tran.

Notes / limitations

  • Requires the accompanying ngspice change (OSDIload in src/osdi/), so it only works with version11's rebuilt ngspice.
  • The provided string parameters are "analysis_name" and "simulator"; an unknown name raises a fatal "unknown $simparam_str" (as for the numeric $simparam with no default).
  • The numeric $simparam(name[, default]) was already supported and is unchanged.