Function Entry: RTOS

rtos

Conversion Function

(rtos number [mode [precision]])

Converts a real or number to a string according to AutoCAD formatting conventions.

String.

None.

This function is part of the language/host formatting boundary, not purely a generic printer primitive.

Autodesk documents the accepted mode values as the linear-unit formats corresponding to LUNITS:
- 1 scientific
- 2 decimal
- 3 engineering
- 4 architectural
- 5 fractional
If mode and precision are omitted, Autodesk documents that rtos uses the current LUNITS and LUPREC settings.
Autodesk documents that the resulting string is affected by UNITMODE for engineering, architectural, and fractional output, and by DIMZIN for zero suppression.
Locale insensitivity (normative). rtos always uses . as the decimal separator regardless of the host's `LC_NUMERIC` / LANG / `LC_ALL` environment, regardless of the OS-level locale, and regardless of the DIMDSEP system variable. DIMDSEP controls only the dimension-text renderer (see § System Variable Entry: DIMDSEP), not the AutoLISP numeric printer. The complementary (atof) rejects locale- comma input the same way — see the (atof "3,5") -> 3.0 probe in § atof. clautolisp matches this contract end-to-end: the value printer (autolisp-value->string, princ / prin1 / vl-*-to-string) is also locale-insensitive — (vl-princ-to-string 3.14) is "3.14" on every locale, every host. User code that wants a comma-separator UI does the substitution itself; the AutoLISP runtime stays in .-land so that (atof (rtos n)) round-trips on every machine.

AutoCAD 2026: documented (per Autodesk reference page).
BricsCAD V26: presumed compatible (no contradicting page found).
Status: AutoCAD documented; BricsCAD presumed-both pending Phase 4 verification.