# bistable.ode
# classic example of a wave joining 0 and 1
#  u_t = u_xx + u(1-u)(u-a)
#
# -cu'=u''+u(1-u)(u-a)
f(u)=u*(1-u)*(u-a)
par c=0,a=.25
u'=up
up'=-c*up-f(u)
init u=1
@ xp=u,yp=up,xlo=-.5,xhi=1.5,ylo=-.5,yhi=.5
done