PDP-10 Archive: 43,50547/pltlib/cmisc1/range.mac from decuslib10-12

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TITLE	RANGE - Returns argument within the range of +/- PI/2
SUBTTL	Dissassembled from OLD:FORLIB.REL by Joe Smith, 8-Sep-83

;ANG=RANGE(ANGLE)       ! ANG has been reduced to be within -1.57 to +1.57

	ENTRY	RANGE		;REAL FUNCTION RANGE (ARG)
	SIXBIT	/RANGE/
RANGE:	MOVE	0,@(16)		;Get argument
	MOVE	1,PI%2		;Get PI/2 for rounding
	CAIGE	0,0		;Positive?
	 MOVNS	1		;No, use -PI/2
	FADR	1,0		;Add in rounding factor
	FDVR	1,PI		;Divide by PI
	MOVEM	1,TEMP		;Save quotient for later testing
	MOVMS	1		;Absolute value of quotient
	FAD	1,BIG		;Shift fractional part into oblivion
	FSB	1,BIG		;Number in AC1 has no fraction
	SKIPGE	TEMP		;If was negative,
	 MOVNS	1		; change quotient to be negative
	FMPR	1,PI		;Get multiple of PI
	FSBR	0,1		;Return number between -PI/2 and +PI/2
	POPJ	17,		;Return from RANGE

PI:	EXP	202622077325	;3.141592653 (MACRO is off in the LSB)
PI%2:	EXP	201622077325	;PI/2 (1.5707963)
BIG:	EXP	233400000000	;Number to drop any fractional part (67108864.0)
TEMP:	EXP	0

	END