#include "CPP_OPTIONS.h"

      _RL FUNCTION ETA_GL_STREAMICE (X, M1, M2, Y0, W)

!      This function smooths out slope discontinuities in a 1D function
!      y(x) is assumed piecewise linear with a slope discontinuity at 0
!      the results is smoothed only on -w/2 < x < w/2

!     X: input variable
!     M1: slope of y where x<0
!     M2: slope of y where x>0
!     Y0: value of y at 0
!     W: width of smoothing

       _RL X, M1, M2, Y0, W
       _RL TMP1, PI

       IF (X<-1.0*W/2.0) THEN
         ETA_GL_STREAMICE = Y0 + M1 * X
       ELSEIF(X>W/2.0) THEN
         ETA_GL_STREAMICE = Y0 + M2 * X
       ELSE
         PI = 3.14159265358979323844D0
         TMP1 = W/PI * COS(PI*X/W)
         ETA_GL_STREAMICE = Y0 + 
     &     M1/2 * (X-W/2+TMP1) + 
     &     M2/2 * (X+W/2-TMP1)
       ENDIF

       RETURN
       END