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#28630 new defect

Wrong conversion from fricas

Reported by:	tmonteil	Owned by:
Priority:	major	Milestone:	sage-9.3
Component:	symbolics	Keywords:	FriCAS
Cc:	hemmecke, whuss, rws, chapoton, mantepse	Merged in:
Authors:		Reviewers:
Report Upstream:	Reported upstream. Developers acknowledge bug.	Work issues:
Branch:		Commit:
Dependencies:		Stopgaps:

Description

As reported on this ask question, we have:

sage: f = polylog(3, x)
sage: f.integral(x, algorithm='fricas')
-x*%iint(x, -log(-x + 1)/x) - (x - 1)*log(-x + 1) + x*polylog(3, x) + x

So, fricas produces something that is ill-interpreted as some %iint symbolic function.

Note that maxima produces the following answer:

sage: f.integral(x, algorithm='maxima')
-x*dilog(x) - (x - 1)*log(-x + 1) + x*polylog(3, x) + x

Change History (11)

comment:1 Changed 12 months ago by tmonteil

Cc hemmecke whuss rws chapoton added

comment:2 Changed 12 months ago by chapoton

Keywords FriCAS added

comment:3 Changed 12 months ago by chapoton

Cc mantepse added

comment:4 Changed 12 months ago by chapoton

This seems to be some kind of bug in Fricas:

sage: f = fricas(polylog(3,x))
sage: f.integrate(x)
              log(- x + 1)
- x %iint(x,- ------------) + x polylog(3,x) + (- x + 1)log(- x + 1) + x
                    x

And the first term can be differentiated (inside Fricas) correctly.

comment:5 Changed 11 months ago by mantepse

More a reminder to myself: SageMath's dilog(x) is FriCAS' dilog(1-x). This is properly reflected in sage.functions.log.py, in class Function_dilog.

So FriCAS should simplify %iint(x, -log(1-x)/x)) to FriCAS dilog(1-x).