def cross(l_goals, r_goals):
"""Takes a list of constraints T <= X and a list
of constraints X <= U and returns the set of constraints
T <= U for every U and T.
We take the empty telescope.
Arguments:
- `l_goals`: a list of goals of the form T <= X
- `r_goals`: a list of goals of the form X <= U
"""
return [Goal(e.nullctxt(), e.Sub(c.prop.lhs, d.prop.rhs))\
for c in l_goals for d in r_goals]
def min_type(types, ctxt):
"""Get the minimum of a list of types. Since it
can be undecidable to compare types in general, we
take T <= U iff it can be proven using
destruct >> trivial. Return None if no minimum is found.
Arguments:
- `types`: a list of types
- `ctxt`: a goal context
"""
for t in types:
min_list = [Goal(e.nullctxt(), e.Sub(t, u))\
for u in types]
min_goal = Goals('min_goal', ctxt, goals=min_list)
min_goal.solve_with(trivial)
if min_goal.is_solved():
return t
return None
def visit_sub(self, expr, *args, **kwargs):
lhs = self.visit(expr.lhs)
rhs = self.visit(expr.rhs)
return e.Sub(lhs, rhs)
def visit_sub(self, expr):
lhs = self.visit(expr.lhs)
rhs = self.visit(expr.rhs)
return e.Sub(lhs, rhs)