substitution in denominator is skipped

[dkrenn]

The following comes very unexpected

sage: ((1+x^2)/x^2).subs({x^2: 42})
43/x^2

The problem is the internal representation as

sage: ((1+x^2)/x^2).operands()
[x^2 + 1, x^(-2)]

Reported upstream as pynac/pynac#186

Depends on #22102

CC: @tscrim @dkrenn

Component: symbolics

Author: Ralf Stephan

Branch/Commit: u/rws/substitution_in_denominator_is_skipped @ 5e39b7b

Issue created by migration from https://trac.sagemath.org/ticket/21071

[rwst]

Description changed:

--- 
+++ 
@@ -12,3 +12,4 @@
 [x^2 + 1, x^(-2)]
 ```
 
+Reported upstream as https://github.com/pynac/pynac/issues/186

[rwst]

Upstream: Reported upstream. Developers acknowledge bug.

[rwst]

comment:2

Note that there is the walkaround of substituting twice, i.e. as given followed by a substitution of the inverse pattern with the inverse replacement, e.g., ((1+x<sup>2)/(x</sup>2)).subs({x^2: 42}).subs({x^-2: 1/42})

[rwst]

Branch: u/rws/substitution_in_denominator_is_skipped

[rwst]

Author: Ralf Stephan

[rwst]

Commit: 67f4651

[rwst]

Changed upstream from Reported upstream. Developers acknowledge bug. to none

[rwst]

comment:4

Remaining fail, hopefully the author(s) can see where they worked around this bug so that their workaround can be removed:

File "src/sage/rings/asymptotic/asymptotics_multivariate_generating_functions.py", line 1717, in sage.rings.asymptotic.asymptotics_multivariate_generating_functions.FractionWithFactoredDenominator.?
Failed example:
    asy # long time
Expected:
    (4/3*sqrt(3)*sqrt(r)/sqrt(pi) + 47/216*sqrt(3)/(sqrt(pi)*sqrt(r)),
     1, 4/3*sqrt(3)*sqrt(r)/sqrt(pi) + 47/216*sqrt(3)/(sqrt(pi)*sqrt(r)))
Got:
    (4/3*sqrt(3)*sqrt(r)/sqrt(pi) + 587/216*sqrt(3)/(sqrt(pi)*sqrt(r)),
     1,
     4/3*sqrt(3)*sqrt(r)/sqrt(pi) + 587/216*sqrt(3)/(sqrt(pi)*sqrt(r)))
**********************************************************************
File "src/sage/rings/asymptotic/asymptotics_multivariate_generating_functions.py", line 1720, in sage.rings.asymptotic.asymptotics_multivariate_generating_functions.FractionWithFactoredDenominator.?
Failed example:
    F.relative_error(asy[0], alpha, [1, 2, 4, 8], asy[1]) # long time
Expected:
    [((3, 3, 2), 0.9812164307, [1.515572606], [-0.54458543...]),
     ((6, 6, 4), 1.576181132, [1.992989399], [-0.26444185...]),
     ((12, 12, 8), 2.485286378, [2.712196351], [-0.091301338...]),
     ((24, 24, 16), 3.700576827, [3.760447895], [-0.016178847...])]
Got:
    [((3, 3, 2), 0.9812164307, [3.958585166], [-3.034364939]),
     ((6, 6, 4), 1.576181132, [3.720460147], [-1.360426775]),
     ((12, 12, 8), 2.485286378, [3.933702631], [-0.5827965202]),
     ((24, 24, 16), 3.700576827, [4.624183269], [-0.2495844526])]

---

New commits:

67f4651

21071: substitution in denominator is skipped