Switch with Infinity

[b1f6c1c4]

Description

How to Reproduce

{MatchQ[Infinity,Infinity],Switch[Infinity,Infinity,True,_,False]}

Output Given

{True,False}

Expected behavior

{True,True}

I don't see any reason this shouldn't evaluate to two Trues. FYI, Wolfram Mathematica gives this result.

Your Environment

docker run --rm -it -p 8000:8000 mathicsorg/mathics -m gui

Software Information
Python
Python: 3.10.6 (main, May 29 2023, 11:10:38) [GCC 11.3.0]
Implementation: CPython 3.10.6.final.0
Mathics3 Software
Mathics3 Django: 7.0.0dev0
Mathics3: 7.0.0dev0
Web Software
Django: 4.2.3
mathics-threejs-backend: 1.3.1
three.js: 146
MathJax: 2.7.9
Numeric Software
mpmath: 1.3.0
Numpy: 1.25.0
Sympy: 1.12
Optional Software
cython: 3.0.0
lxml: 4.9.3
networkx: 3.1
nltk: 3.8.1
psutil: 5.9.5
skimage: 0.21.0
scipy: 1.10.1
wordcloud: 1.9.2
Settings
Django
ALLOWED_HOSTS: []
DEBUG: True
DISPLAY_EXCEPTIONS: False
Mathics3 Django
Settings`$PreferredBackendMethod: "sympy"
This sets whether to use mpmath, numpy or Sympy for numeric and symbolic constants and methods, when there is a choice.
Settings`$QuotedStrings: 
If this Boolean variable is set False, hide the quotes when the top-level value is a string.
Settings`$TraceGet: 
If this Boolean variable is set True, 'Get' traces the lines it reads that start a new expression.
Settings`$UseSansSerif: 
If this Boolean variable is set True, MathMLForm uses a Sans-Serif font.
System information
User Name: mathics
Process ID: 1
System Time Zone: -6.0 hours from UTC
File Paths
Base Directory: /usr/src/app/mathics-core/mathics
Home Directory: /usr/src/app
Installation Directory: /usr/src/app/mathics-core/mathics
Root Directory: /
Temporary Directory: /tmp
Workspace Database File: /usr/src/app/.local/var/mathics/mathics.sqlite
Doctest Data: /usr/src/app/mathics-core/mathics/doc/doc_html_data.pcl
Machine information
Machine Name: 3021451861bc
Machine: linux
Processor Type: x86_64
Memory Available: 24231600128
System Memory: 33357537280
Machine Precision: 15.954589770191003
Mathics3 Setttings
Maximum Digits allowed in a String: unlimited
System Charecter Encoding: UTF-8
Time format is 12 Hour?: False
Connection Information
HTTP User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36
Remote User:
Remote Address: 172.17.0.1
Remote Host:

Workarounds

Use If[MatchQ[]] instead of Switch

Priority

Additional context

[rocky]

I see what is happening, but I am at a total loss for how to address.

Infinity gets converted to DirectedInfiity[1], but our "Match" method sees this as an atomic symbol and uses an matcher that is an instance of AtomPattern.

Something is mismatched in the way we evaluate this.

@mmatera Do you have thoughts on this?

[mmatera]

This is how Switch works in WMA:

In Mathics, it works in the same way:

In[1]:= TraceEvaluation[Switch[Infinity,Infinity,True,_,False]]
    Evaluating: System`Switch[System`Infinity, System`Infinity, System`True, System`Blank[], System`False]
      Evaluating: System`Switch
      Evaluating: System`Infinity
      -> System`DirectedInfinity[1]
      Evaluating: System`DirectedInfinity[1]
        Evaluating: System`DirectedInfinity
      Evaluating: System`False
    -> System`False
Out[1]= False

So the problem seems to be localized in the Mathics implementation of Switch.

[mmatera]

Switch has the attribute HoldRest to avoid evaluating all the conditions before the comparison. What we had forgot in Mathics was to evaluate each pattern before the comparison. #957 fixes this.

[rocky]

@b1f6c1c4 At some point in the near future I will try to update the docker image.
@mmatera At some point in the future we should try to add a TracePrint[] and TraceAction[].

[mmatera]

@rocky: what is TraceAction?

[rocky]

@rocky: what is TraceAction?

It is listed below TracePrint in your output above. I assumed this TracePrint was implemented using TraceAction by rewriting this and substituting Print in there somewhere.

[mmatera]

Ah, OK. TraceAction is an option of TracePrint. I will think about how to implement this.