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PLCOPEN-N2: Define type prefixes for variables

Variable names should start with a configurable type-based prefix (Hungarian notation).

Why is it bad?​

Without a type prefix convention, the reader has to jump back to the declaration block every time they meet a variable to remember whether it is an INT, a BOOL, a REAL or something else. Adopting a short prefix per elementary type — i for INT, x for BOOL, r for REAL — keeps the reader in the flow at the point of use and surfaces accidental type mismatches during code review.

Configuration​

This lint is opt-in. Enable it from iec_checker.json:

{
  "detectors": { "enabled": ["PLCOPEN-N2"] },
  "naming_conventions": {
    "type_prefixes": { "INT": "i", "BOOL": "x", "REAL": "r" }
  }
}

Keys are elementary type names exactly as spelled in IEC 61131-3 (INT, BOOL, REAL, DINT, SINT, …). Only elementary-typed variables are checked; derived / user-defined types are covered by PLCOPEN-N10.

Example​

PROGRAM program0
  VAR
    iCounter : INT;
    Counter  : INT;    (* PLCOPEN-N2 — missing "i" prefix *)
    xReady   : BOOL;
    Ready    : BOOL;   (* PLCOPEN-N2 — missing "x" prefix *)
  END_VAR
END_PROGRAM

Use instead:

PROGRAM program0
  VAR
    iCounter : INT;
    iResult  : INT;
    xReady   : BOOL;
    xDone    : BOOL;
  END_VAR
END_PROGRAM

Resources​

  1. PLCOpen Software Construction Guidelines