Improve the set handler #20650

sayandip18 · 2020-12-22T23:11:52Z

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Fixes #20535

Brief description of what is fixed or changed

The set handler can now deal with symbolic intervals

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…ections of intervals

sympy-bot · 2020-12-22T23:11:53Z

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Fixes #20535 

#### Brief description of what is fixed or changed
The set handler can now deal with symbolic intervals

#### Other comments


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sayandip18 · 2020-12-22T23:14:33Z

Certain tests, for instance sympy/sets/tests/test_sets.py:test_intersect1, which are throwing error now need to be modified accordingly

oscarbenjamin · 2020-12-23T01:52:07Z

sympy/sets/handlers/intersection.py

+        else:
+            start = Max(a.start, b.start)
+            end = Min(a.end, b.end)
+            if a.start > b.start:


This could raise for symbolic start and end. It could be if is_gt(a.start, a. end).

sayandip18 · 2020-12-24T19:22:48Z

>>> Intersection(Interval(1, x), Interval(2, 3)).contains(y)
(2 <= y) & (y <= Min(3, x))
>>> And(2<=y, y<= Min(3, x))
(y >= 2) & (y <= Min(3, x))
>>> Intersection(Interval(1, x), Interval(2, 3)).contains(y)==And(2<=y, y<= Min(3, x))
False

This should be True but I don't know why I'm getting False

sayandip18 · 2020-12-25T19:47:07Z

test_latex_intersection() of sympy/printing/tests/test_latex.py failed. latex(Intersection(Interval(0, 1), Interval(x, y))) now cannot work with raw string for some reason. Removing the r from the beginning of the string makes it work perfectly. Apparently, this change is somehow breaking certain things. Should I still continue @oscarbenjamin ?

oscarbenjamin · 2020-12-26T02:09:42Z

Apparently, this change is somehow breaking certain things. Should I still continue

Without knowing the cause of the breakage it's impossible to answer that question. What "breaks" and how?

sayandip18 · 2020-12-28T16:47:13Z

What "breaks" and how?

Both of my above comments.

sayandip18 · 2020-12-28T16:53:55Z

This test now returns False only if I treat the string as a normal string instead of a raw string, i.e. if I remove the r. and I'm still unable to figure out why this occurs.

oscarbenjamin · 2020-12-28T17:47:04Z

In [5]: 2 < y
Out[5]: y > 2

In [6]: S(2) < y
Out[6]: 2 < y

In [7]: Intersection(Interval(0, 1), Interval(x, y))
Out[7]: [Max(0, x), Min(1, y)]

oscarbenjamin · 2021-01-01T21:20:39Z

sympy/core/tests/test_args.py

@@ -889,7 +889,7 @@ def test_sympy__sets__sets__Intersection():
    x = Symbol('x')
    y = Symbol('y')
    S = Intersection(Interval(0, x), Interval(y, 1))
-    assert isinstance(S, Intersection)
+    assert isinstance(S, Interval)
    assert _test_args(S)


This test should is supposed to test Intersection so if it doesn't give an intersection then something else needs to be used as the arguments.

oscarbenjamin · 2021-01-01T21:21:49Z

sympy/printing/pretty/tests/test_pretty.py

-    ucode_str = '[x, y] ∩ [z, w]'
-    ascii_str = '[x, y] n [z, w]'
+    ucode_str = '[Max(x, z), Min(w, y)]'
+    ascii_str = '[Max(x, z), Min(w, y)]'


This is supposed to be a test of printing an Intersection so if it doesn't give an intersection then something other than interval should be used as the arguments

oscarbenjamin · 2021-01-01T21:22:12Z

sympy/printing/tests/test_latex.py

@@ -917,7 +917,7 @@ def test_latex_union():

 def test_latex_intersection():
    assert latex(Intersection(Interval(0, 1), Interval(x, y))) == \
-        r"\left[0, 1\right] \cap \left[x, y\right]"
+        r"\left[\max\left(0, x\right), \min\left(1, y\right)\right]"


This is also a test for printing Intersection

oscarbenjamin · 2021-01-02T13:50:52Z

I'm not sure now whether having this evaluate automatically is a good idea or whether it should really be part of simplify or rewrite or something like that.

We do need a function that can rewrite an intersection of intervals using Max but that perhaps should not happen automatically when calling Intersection(interval1, interval1). If we had a function for doing that then it could be used by integrate.

Improve the set intersections handler package to better handle inters…

268dc69

…ections of intervals

oscarbenjamin reviewed Dec 23, 2020

View reviewed changes

Abdullahjavednesar added the sets label Dec 23, 2020

modifying tests

4f12806

sayandip18 added 2 commits December 30, 2020 03:57

fix tests

e43f9e2

fix test 2

fcecfbf

oscarbenjamin reviewed Jan 1, 2021

View reviewed changes

Maelstrom6 mentioned this pull request Jan 28, 2021

List of issues with the integrate module identified by the stats module #20872

Open

oscargus mentioned this pull request Sep 12, 2021

Better intersection of symbolic intervals #22083

Open

github-actions bot added the Merge conflict label Oct 26, 2022

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Improve the set handler #20650

Improve the set handler #20650

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