Opened 7 years ago

Closed 7 years ago

## #16998 closed defect (fixed)

Reported by: Owned by: jmantysalo minor sage-6.4 combinatorics Jori Mäntysalo Christian Stump N/A b5d4a96 b5d4a968eb151d9d13e257c602eaf32c4d883288

Documentation for `is_graded()` on `posets.py` says "Note that every graded poset is ranked, but the converse is not true.", whereas `hasse_diagram.py` says "A poset is *graded* if it admits a rank function."

Somebody knowing area should check this.

Somehow relating to this: note in `is_graded` on `posets.py` should be removed, see #13223.

### comment:1 Changed 7 years ago by jmantysalo

Actually it seems that `is_graded()` is not called at all. I guess it should be deprecated.

### comment:2 Changed 7 years ago by jmantysalo

• Description modified (diff)

### comment:3 follow-up: ↓ 4 Changed 7 years ago by stumpc5

Some time ago (maybe 2 years), we (a few Sage-Combinat people) agreed on the following definitions:

A poset is graded if all maximal chains have the same length.

A poset is ranked if it admits a rank function. A rank function f is a integer valued function on the vertices of a (finite) poset P such that

• f(p) = 0 if p is a minimal element in P, and
• f(q) = f(p)+1 if p \prec q is a cover relation in P.

### comment:4 in reply to: ↑ 3 ; follow-up: ↓ 5 Changed 7 years ago by jmantysalo

Some time ago (maybe 2 years), we (a few Sage-Combinat people) agreed on the following definitions:

That's good. It has been done on `posets.py`, but `hasse_diagram.py` still contains older(?) definition. Hence it needs correcting.

### comment:5 in reply to: ↑ 4 ; follow-up: ↓ 7 Changed 7 years ago by stumpc5

That's good. It has been done on `posets.py`, but `hasse_diagram.py` still contains older(?) definition. Hence it needs correcting.

You are welcome to do so -- I'll be reviewing it then...

### comment:7 in reply to: ↑ 5 Changed 7 years ago by jmantysalo

• Authors set to Jori Mäntysalo
• Commit set to d66dffdbb4abbc684fcc771c5c38886a3cbc5849
• Status changed from new to needs_review

You are welcome to do so -- I'll be reviewing it then...

Ok, ok... Here it is.

New commits:

 ​d66dffd `Deprecation of is_graded on hasse diagram.`

### comment:8 follow-up: ↓ 9 Changed 7 years ago by stumpc5

Why did you decide to deprecate it rather than checking whether the Hasse diagram is graded?

### comment:9 in reply to: ↑ 8 Changed 7 years ago by jmantysalo

Why did you decide to deprecate it rather than checking whether the Hasse diagram is graded?

What if somebody has really used `is_graded()` directly on hasse diagram, expecting it to say `True` if the hasse diagram is ranked? Of course nobody should do that, but instead use poset.

And on sage-devel list we discuss about moving code away from `hasse_diagram.py`.

### comment:10 Changed 7 years ago by stumpc5

Okay, sounds reasonable... could you leave one sentence in the documentation saying what this function returns?

### comment:11 Changed 7 years ago by git

• Commit changed from d66dffdbb4abbc684fcc771c5c38886a3cbc5849 to b5d4a968eb151d9d13e257c602eaf32c4d883288

Branch pushed to git repo; I updated commit sha1. New commits:

 ​b5d4a96 `More docs for is_graded().`

### comment:12 Changed 7 years ago by stumpc5

• Status changed from needs_review to positive_review

### comment:13 Changed 7 years ago by vbraun

• Status changed from positive_review to needs_work

reviewer name

### comment:14 Changed 7 years ago by stumpc5

• Reviewers set to Christian Stump
• Status changed from needs_work to positive_review

### comment:15 Changed 7 years ago by vbraun

• Branch changed from u/jmantysalo/documentation_conflict_on_is_graded__ to b5d4a968eb151d9d13e257c602eaf32c4d883288
• Resolution set to fixed
• Status changed from positive_review to closed
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