findall(f .== f[1]), TypeError: non-boolean (Num) used in boolean context

[xiang-yu]

Hi everyone,

Any thoughts on the following error?
Note that SymPy in Julia works.

f = Symbolics.variables(:f, 1:Q)

3-element Vector{Num}:
f₁
f₂
f₃

findall(f .== f[1])

TypeError: non-boolean (Num) used in boolean context
Stacktrace:
[1] iterate
@ ./iterators.jl:514 [inlined]
[2] iterate
@ ./generator.jl:44 [inlined]
[3] grow_to!
@ ./array.jl:855 [inlined]
[4] collect
@ ./array.jl:779 [inlined]
[5] findall(A::Vector{Num})
@ Base ./array.jl:2402
[6] top-level scope
@ REPL[126]:1

[ChrisRackauckas]

== on symbolics is not a boolean, so it cannot be used in boolean comparisons. Did you instead mean findall(isequal.(f,f[1]))?

[xiang-yu]

isequal works like a charm! Thanks a lot, @ChrisRackauckas . Any chance this can be added to the instruction of Symbolics?

[ChrisRackauckas]

It's already in the docs https://symbolics.juliasymbolics.org/stable/manual/faq/. I extended it as well: https://github.com/JuliaSymbolics/Symbolics.jl/blob/master/docs/src/manual/faq.md#equality-and-set-membership-tests. Let me know if anything else would clear up the confusion.

[ChrisRackauckas]

x