.TITLE DATAN  COMPUTE ARCTANGENT FOR DOUBLE ARGUMENT
/COPYRIGHT 1970, DIGITAL EQUIPMENT CORP., MAYNARD, MASS.
       .GLOBL DATAN,.DA,.AO,.DD
/             CALLING SEQUENCE
/      JMS*   (DTAN)          SUBR CALL
/      JMP    .+2             SUBR RETURN
/      CAL/XCTADDR            ADDR OF ARGUMENT (XCT IF INDIRECT)
/
DATAN  CAL    0              /ENTRY-EXIT
       JMS*   .DA            /GET ARGUMENT (.DA)
       JMP    DTAN02
DTAN01 CAL    0              /ARGUMENT
DTAN02 JMS*   .AO            /LOAD DOUBLE (.AO)
       .DSA   DTAN01+400000  / (ARG)
       JMS*   .DD            /COMPUTE ARCTANGENT (.DD)
       JMP*   DATAN
       .END