--- /dev/null
+/
+/
+/ SUBROUTINE DATAN(X)
+/
+/ VERSION 5A 4-26-77 (MH)
+/
+/X,THE ARGUMENT, IS REDUCED TO
+/0<X<1/2
+/BY THE IDENTITIES:
+/ATAN(-X)=-ATAN(X)
+/IF X>1.0 THEN ATAN(X)=PI/2 - ATAN(1/X)
+/IF .5<X<1.0 THEN ATAN(X)=ATAN(1/2)+ATAN(2*X-(1/(X+2)))
+/ATAN(X)=X FOR X<2^(-15)
+/
+/
+/
+ SECT DATAN
+ JA #DATAN
+ DPCHK
+/
+ TEXT +DATAN +
+DATNXR, SETX XRDATN
+ SETB BPDATN
+BPDATN, F 0.0
+XRDATN, F 0.0
+DATFP1, F 1.0
+ F 0.0
+DATLOW, -15
+ 2000
+ 0000
+ 0000
+ 0000
+ 0000
+/
+ ORG 10*3+BPDATN
+ FNOP
+ JA DATNXR
+ 0
+DATRTN, JA .
+/
+LAMBDA, 0004
+ 3057
+ 7537
+ 4017
+ 0276
+ 4536
+DATB0, 0005
+ 3221
+ 3522
+ 3121
+ 3352
+ 5066
+DATA1, 0007
+ 5372
+ 4104
+ 3437
+ 1766
+ 6167
+DATB1, 0003
+ 3135
+ 1757
+ 0565
+ 4141
+ 4270
+DATA2, 0001
+ 5473
+ 7524
+ 1112
+ 4701
+ 2723
+DATB2, 0002
+ 2065
+ 4070
+ 1015
+ 2710
+ 3176
+DATA3, 7775
+ 5374
+ 4326
+ 3317
+ 1675
+ 3124
+DATB3, 0001
+ 2410
+ 5255
+ 0370
+ 2076
+ 6374
+PIS2, 0001
+ 3110
+ 3755
+ 2421
+ 0264
+ 3013
+ATN1S2, 7777
+ 3553
+ 0634
+ 0530
+ 3443
+ 6406
+DATP5, 7777
+ 3777
+ 7777
+ 7777
+ 7777
+ 7776
+X, F 0.0
+ F 0.0
+C0, F 0.0
+ F 0.0
+DT1, F 0.0
+ F 0.0
+DATFP2, F 2.0
+ F 0.0
+Z, F 0.0
+ F 0.0
+/
+/PICK UP RETURN AND ARGUMENT
+ BASE 0
+#DATAN, STARTD
+ FLDA 10*3
+ FSTA DATRTN
+ FLDA 0
+ SETX XRDATN
+ SETB BPDATN
+ BASE BPDATN
+ LDX 1,1
+ FSTA BPDATN
+ FLDA% BPDATN,1
+ FSTA BPDATN
+ STARTE
+ FLDA% BPDATN /GET X
+ LDX -1,0 /SIGN
+ JGE .+5
+ LDX 0,0 /SAVE SIGN
+ FNEG
+ FSTA X /SAVE ARG
+/
+/CHECK ARGAINST LOWER LIMIT
+ FLDA X
+ FSUB DATLOW /TOO SMALL?
+ JLE DATGO /YES ATAN(X)=X
+ LDX -1,1
+ FCLA
+ FSTA C0
+/
+/REDUCE X TO RANGE 0<X<.5
+DATA, FLDA X
+ FSUB DATFP1
+ JLE DATB />1?
+ FLDA DATFP1 /YES
+ FDIV X /X=1/X
+ LDX 0,1 /SET FLAG
+ FSTA X
+DATB, FLDA X
+ FSUB DATP5 />= .5
+ JLT DATC
+ FLDA X /X=(2X-1)/(X+2)
+ FADD DATFP2
+ FSTA DT1 /TEMP
+ FLDA X
+ FMUL DATFP2
+ FSUB DATFP1
+ FDIV DT1
+ FSTA X
+ FLDA ATN1S2 /C0=ATAN(1/2)
+ FSTA C0
+/COMPUTE ATAN USING ALGORITHM
+DATC, FLDA X
+ FMUL X
+ FSTA Z /Z=X*X
+ FLDA Z
+ FADD DATB3 /Z+B3
+ FSTA DT1
+ FLDA DATA3
+ FDIV DT1 /A3/(Z+B3)
+ FADD DATB2
+ FADD Z /ADD Z+B2
+ FSTA DT1 /TEMP
+ FLDA DATA2 /A2/TEMP
+ FDIV DT1
+ FADD DATB1
+ FADD Z /ADD Z +B1
+ FSTA DT1 /TEMP
+ FLDA DATA1 /A1/TEMP
+ FDIV DT1
+ FADD DATB0 /ADD Z+B0
+ FADD Z
+ FSTA DT1
+ FLDA LAMBDA /LAMBDA*X
+ FMUL X
+ FDIV DT1 /DIV BY THE REST
+ FADD C0
+ FSTA X
+ JXN DATD,1 /WAS X>1 ORIGINALLY?
+ FLDA PIS2 /Y ATAN(X)=PI/2-ATAN(X)
+ FSUB X
+DATD, JXN DATRTN,0 /WAS X<0?
+ FNEG /Y
+ JA DATRTN
+DATGO, FLDA X
+ JA DATD
+\f
projects / pdp8.git / blobdiff