chained inequalities bug in add_constraint to MixedIntegerLinearProgram #12091
Description
This ticket was originally started to address problems now dealt with in #13646.
Still, the following (chained inequalities don't work) needs to be fixed:
sage: p = MixedIntegerLinearProgram()
sage: b = p.new_variable()
sage: b[0] <= b[1] <= 2 # This is not ok
x_1 <= 2
sage: (b[0] <= b[1] <= 2).constraints # Not ok
[x_1, 2]
sage: 1 >= b[1] >= 2*b[0] # Not ok (note that without #13646 this returns False)
2 x_0 <= x_1
sage: b[2] >= b[1] >= 2*b[0] # Not ok
2 x_0 <= x_1
See also this sage-support thread.
Apply
Depends on #13650
CC: @nathanncohen @kini @vbraun
Component: linear programming
Author: Volker Braun
Reviewer: Dmitrii Pasechnik
Merged: sage-5.5.rc0
Issue created by migration from https://trac.sagemath.org/ticket/12091