A fix for `occursin`

[TorkelE]

The current implementation causes occasional ambiguity errors. This fixes that.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 15 lines in your changes missing coverage. Please review.

Project coverage is 10.17%. Comparing base (79c4e92) to head (a8e987f). Report is 209 commits behind head on master.

Files	Patch %	Lines
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```diff @@ Coverage Diff @@ ## master #1139 +/- ## =========================================== - Coverage 77.07% 10.17% -66.90% =========================================== Files 32 36 +4 Lines 3533 3616 +83 =========================================== - Hits 2723 368 -2355 - Misses 810 3248 +2438 ```

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[TorkelE]

Now replaces the replace and occursin Symbolics functions with the replacenode and hasnode functions (within the context where these were used). This prevents some clashes with occursin defined for symbolic in SymboliUtils.

[ChrisRackauckas]

Rebase.

[TorkelE]

Update:

• rebased.
• change repalcenode to replace.
• make fixpoint = false an optional argument to the replace function (rather than being in the internal _replace).

[TorkelE]

When I tried to check if old replace worked again, it didn't. However, that was still on SymbolicsUtils 1.6, as v2.0 is not compatible with the latest Symbolics.

[TorkelE]

@shashi There is a near instant error, but that seems to be due to a package incompatibility error:

ERROR: LoadError: Unsatisfiable requirements detected for package SymbolicUtils [d1185830]:
 SymbolicUtils [d1185830] log:
 ├─possible versions are: 0.1.0-2.0.2 or uninstalled
 ├─restricted to versions 2.0.2-2 by Symbolics [0c5d862f], leaving only versions: 2.0.2
 │ └─Symbolics [0c5d862f] log:
 │   ├─possible versions are: 5.29.0 or uninstalled
 │   └─Symbolics [0c5d862f] is fixed to version 5.29.0
 └─restricted by compatibility requirements with TermInterface [8ea1fca8] to versions: [0.1.0-0.14.0, 1.0.0-1.5.1] or uninstalled — no versions left
   └─TermInterface [8ea1fca8] log:
     ├─possible versions are: 0.1.0-1.0.0 or uninstalled
     └─restricted to versions 1 by Symbolics [0c5d862f], leaving only versions: 1.0.0
       └─Symbolics [0c5d862f] log: see above

This PR does not changes any project files, so should be related to master Symbolics?

[ChrisRackauckas]

Rebase

[TorkelE]

Ok, this passes now, exept for:

• MTK downstream, but again that is an incompatibility of packages in MTK.
• This test: Build Targets Test | 2 1 3 2.2s

Small note, currently the hasnode and replace functions only work on symbolic expressions:

using Symbolics
@variables x y z
expr = x^2 + y
hasnode(x^2, expr) # true
Symbolics.replace(expr, x^2 => z) # y + z

however, if the expression is just a number, these fails:

expr = 10
hasnode(x^2, expr) # ERROR: MethodError: no method matching hasnode(::Num, ::Int64)
Symbolics.replace(expr, x^2 => z) # ERROR: MethodError: no method matching replace(::Int64, ::Pair{Num, Num})

if you were to apply these to e.g. lhs and rhs of an equation, you might run into a problem for e.f. 0 ~ x + y. Since replace is not a general function, maybe it should not be changed, but would it make sense to add a dispatch for hasnode:

hasnode(r::Union{Function, Num, Symbolic}, y::Number) = false

[ChrisRackauckas]

This test: Build Targets Test | 2 1 3 2.2s

Looks like this PR broke it.

[TorkelE]

MTK downstream still fail due to some incompatibility, but otherwise all good.