@spec parse_file(String.t(), boolean()) ::
  {:ok, BeHOLd.Data.Problem.t()} | {:error, String.t()}

Parses a TPTP file in TH0 syntax at the proveded path into a Problem structure. Returns {:error, reason} if a problem occured when reading the file.

This function serves two purposes: parsing a file from the TPTP problem library (https://tptp.org/TPTP/) or a custom problem file given by the user.

The default is to parse a file from the TPTP problem library. In that case, the flag is_tptp should be set to true. This also requires an environment variable TPTP_ROOT which points to the unpacked root folder of the TPTP problem library. Setting this environment variable may require a system restart before Elixir recognizes it.

When parsing a custom problem file, the flag is_tptp should be set to false. problem should contain the absolute path to the problem file. Note that imports of custom files are not supported. Only axioms from the TPTP problem library can be imported (this also requires the TPTP_ROOT environment variable to be set).

@spec parse_string(String.t(), String.t()) ::
  {:ok, BeHOLd.Data.Problem.t()} | {:error, String.t()}

Parses a string representing a problem file in TPTP's TH0 syntax into a Problem structure.

The parsing of content only supports including files from the TPTP problem library. If such includes are present, make sure that the TPTP_ROOT environment variable is set.

The path does not need to be specified when calling this method. It is purely for keeping track of the file name from a call to parse_file/2.