setabc.for

C       SETABC.FOR              D.H. KLATT              8/1/78
C
C       CONVERT FORMANT FREQENCIES AND BANDWIDTH TO RESONATOR
C       DIFFERENCE EQUATION CONSTANTS

        elemental SUBROUTINE SETABC(F,FB,A,B,C)
        use, intrinsic:: iso_fortran_env, only: int16, sp=>real32
        implicit none
        
        INTEGER(int16), intent(in) :: F,FB
        REAL(sp), intent(out) :: A, B, C
        real(sp) R, PIT, TWOPIT
        COMMON /PIXX/ PIT,TWOPIT
C
C---REPLACE BY R=EXPTAB(FB) FOR FASTER EXECUTION
        R=EXP(-PIT*FLOAT(FB))
        C=-R*R
C---REPLACE BY B=COSTAB(F) FOR FASTER EXECUTION
        B=2.*R*COS(TWOPIT*FLOAT(F))
        A=1.-B-C
620     CONTINUE
C     IF F IS MINUS, COMPUTE A,B,C FOR A ZERO PAIR
        IF (F.GE.0) RETURN
630     A=1./A
        B=-A*B
        C=-A*C

        END SUBROUTINE SETABC