SUBROUTINE YDCF(X,GRAT,A,WAVE)
*
*  Module number: 14.8.2.2
*
*  Module name: YDCF
*
*  Keyphrase:
*  ----------
*       Compute wavelength for given x position
*
*  Description:
*  ------------
*       This routine computes the wavelength given the x (diode position)
*
*  FORTRAN name: YDCF
*
*  Keywords of accessed files and tables:
*  --------------------------------------
*       none
*  Subroutines Called:
*  -------------------
*       none
*  History:
*  --------
*  Version      Date        Author          Description
*     1         Jan 88  D. Lindler      Designed and coded
*-------------------------------------------------------------------------------
C
C INPUT PARAMETERS
C
C       X - X POSITION (DIODE NUMBER) REAL*8
C       GRAT - GRATING MODE CHAR*3
C       A - COEFFICIENTS REAL*8 VECTOR
C
C OUTPUT PARAMETERS
C
C       WAVE - WAVELENGTH (REAL*8)
C
C----------------------------------------------------------------------------
        DOUBLE PRECISION  X,A(*),WAVE,XX
        CHARACTER*3     GRAT
C
C IS IT THE PRISM
C
        IF(GRAT.EQ.'PRI')THEN
                XX=X-A(6)
                WAVE=A(1)+A(2)/XX+A(3)/XX**2+A(4)/XX**3+A(5)/XX**4
            ELSE
C
C GRATING MODE
C
                WAVE=A(1)+A(2)*X+A(3)*X**2+A(4)*X**3
        ENDIF
        RETURN
        END