pbw_algebra breaks when used with field over Laurent polynomial ring

[felix-roehrich]

Describe the bug
When trying to construct a PBW algebra using pbw_algebra where the underlying field is a field of fractions (constructed from a Laurent polynomial ring) the constructor throws errors. Also previously working calls fail afterwards.

To Reproduce

using Oscar

A, v = LaurentPolynomialRing(ZZ, "v")
Qv = fraction_field(A)
R, x = polynomial_ring(Qv, 2)
rels = R[0 x[1]*x[2]; 0 0]
pbw_algebra(R, rels, deglex(R))
# *throws on first call*
# ERROR: Could not call function
# Stacktrace:
# [1] call_singular_library_procedure
#   @ ~/.julia/packages/CxxWrap/VnssN/src/CxxWrap.jl:624 [inlined]
# ...
# *and on further calls*
# ERROR: cfRead is undefined for Coeffs(17)
# error occurred in or before nctools.lib::ndcond line 555: `parameter list #;  `
# cfRead is undefined for Coeffs(17)
# error occurred in or before nctools.lib::ndcond line 559: `  int N = 1;`
# expected int-expression. type 'help int;'
# ...

The following code works, but not after executing 1.

using Oscar

A, v = QQ["v"]
Qv = fraction_field(A)
R, x = polynomial_ring(Qv, 2)
rels = R[0 x[1]*x[2]; 0 0]
pbw_algebra(R, rels, deglex(R))

Expected behavior
No errors, or error that certain fields cannot be handled.

System (please complete the following information):
Please paste the output of Oscar.versioninfo(full=true) below. If this does
not work, please paste the output of Julia's versioninfo() and your Oscar
version.

julia> Oscar.versioninfo(full=true)
OSCAR version 0.13.1-DEV
  combining:
    AbstractAlgebra.jl   v0.32.5
    GAP.jl               v0.9.8
    Hecke.jl             v0.22.1
    Nemo.jl              v0.36.2
    Polymake.jl          v0.11.6
    Singular.jl          v0.18.16
  building on:
    Antic_jll               v0.201.500+0
    Arb_jll                 v200.2300.0+0
    Calcium_jll             v0.401.100+0
    FLINT_jll               v200.900.7+0
    GAP_jll                 v400.1200.200+7
    Singular_jll            v403.208.800+0
    libpolymake_julia_jll   v0.10.5+0
    libsingular_julia_jll   v0.40.3+0
    polymake_jll            v400.1000.1+0
See `]st -m` for a full list of dependencies.

Julia Version 1.9.3
Commit bed2cd540a1 (2023-08-24 14:43 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (x86_64-apple-darwin22.4.0)
  CPU: 8 × Intel(R) Core(TM) i7-8557U CPU @ 1.70GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-14.0.6 (ORCJIT, skylake)
  Threads: 1 on 8 virtual cores
Official https://julialang.org/ release

[fingolfin]

@hannes14 will look into the first issue.

The second one looks like an instance of oscar-system/Singular.jl#671

[joschmitt]

Closing this: the example works now.