oscat/CHK_REAL.EXP at master · simsum/oscat · GitHub

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(* @NESTEDCOMMENTS := 'Yes' *)
(* @PATH := '\/Logic\/gate logic' *)
(* @OBJECTFLAGS := '0, 8' *)
(* @SYMFILEFLAGS := '2048' *)
FUNCTION CHK_REAL : BYTE
VAR_INPUT
	X : REAL;
END_VAR
VAR
	pt : POINTER TO DWORD;
	tmp : DWORD;
END_VAR


(*
version 1.0	20. jan. 2011
programmer 	hugo
tested by		tobias

this function checks a floating point variable of type real (IEEE754-32Bits) for NAN and infinity
RETURN values: #0 = normal value, #20 = +infinity, #40 = -infinty, #80 = NAN

*)

(* @END_DECLARATION := '0' *)
pt := ADR(X);				(* move real to dword, real_to_dword does not work becasze it treats dword as a number on many systems *)
tmp := ROL(pt^,1);			(* rotate left foir easy checking, sign will be at lease significant digit *)
IF tmp < 16#FF000000 THEN
	CHK_REAL := 16#00;		(* normalized and denormalized numbers *)
ELSIF tmp = 16#FF000000 THEN
	CHK_REAL := 16#20;		(* X is +infinity see IEEE754 *)
ELSIF tmp = 16#FF000001 THEN
	CHK_REAL := 16#40;		(* X is -infinity see IEEE754 *)
ELSE
	CHK_REAL := 16#80;		(* X is NAN see IEEE754 *)
END_IF;


(* revision history
hm	 20. jan. 2011	rev 1.0
	original version

*)
END_FUNCTION