from gekko import GEKKO
# define new GEKKO model
m = GEKKO()
# parameter
x = m.Param(-0.5)
# define new binary variable
intb = m.Var(0,lb=0,ub=1,integer=True)
# define y
y = m.Var()
# define equations
m.Equation((1-intb)*x <= 0)
m.Equation(intb * (-x) <= 0)
# output
m.Equation(y==(1-intb)*(-x) + intb*x)
# solve with APOPT (MINLP solver)
m.options.SOLVER=1
m.solve()
# print solution
print('x: ' + str(x.value))
print('intb: ' + str(intb.value))
print('y: ' + str(y.value))