cet-is » fhicl » fhicl-cpp

A few questions:

• Would you be opposed to renaming the facility 'fhicl-get-value'?
• The code supports printing only atomic values and sequence-of-atomic values. Is there any reason why the fhiclcpp-provided implementation should not support printing any kind of value corresponding to a key (e.g. a FHiCL table)?
• Is it acceptable for the printout of a sequence to look like:
  

  $ fhicl-get-value my.nested.sequence my.fcl
  [
    a,
    b,
    c
  ]
  

Upon further analysis and development, I propose that the utility be called fhicl-inspect, which will have the following command-line options:

$ fhicl-inspect --help
fhicl-inspect (--key|--keys-for) key [-c] <file>
Options:
  -h [ --help ]         Produce this help message
  -c [ --config ] arg   Input configuration file
  --key arg             Fully-qualified parameter key (a.b.c.d)
  --keys-for arg        Print the top-level keys of the fully-qualified 
                        parameter key, which must correspond to a FHiCL table.

Printed format¶

The following configuration:

table: {
  nested_value: 4
}
sequence: [a, b, @nil]

yields the following printouts:

$ fhicl-inspect --key table.nested_value test.fcl
table.nested_value: 4

$ fhicl-inspect --key table test.fcl
table: {
   nested_value: 4
}

$ fhicl-inspect --key sequence test.fcl
sequence: [
   "a",
   "b",
   @nil
]

$ fhicl-inspect --keys-for table test.fcl
nested_value

Please let me know if you have any concerns regarding this. I will need to determine how to handle the FHiCL file lookup policy. As FHiCL does not prescribe a specific policy, a user may wish to have a policy that differs from an art context. However, I will explore the possibilities, probably defaulting to the policy art uses.

I have completed a first implementation (fhicl-cpp:2c927d), which I believe conforms to your request. Upon further thought, it became clear that this feature is intended to mimic the C++ interface of fhicl::ParameterSet::get<T>(key) and fhicl::ParameterSet::get_names().

Executable name and program options¶

The name of the executable is fhicl-get. Just like ParameterSet::get, the purpose of fhicl-get is to return the value corresponding to a parameter key. The supported command-line options are:

$ fhicl-get --help 

Usage: fhicl-get [options] <key> <file>

Required parameters:
  <key>       A fully-qualified parameter key of the form 'a.b.c.d'
  <file>      A valid FHiCL document that contains the parameter with
              the name as specified for <key>

Supported options:
  -h [ --help ]                        Produce this help message
  --atom-as arg                        Return value for the supplied key as an 
                                       atom with the provided C++ type.
  --sequence-of arg                    Return value for the supplied key as a 
                                       sequence of the provided C++ type.
  --names-in                           Print the top-level names of the 
                                       supplied key, which must correspond to a
                                       FHiCL table.
  --lookup-policy arg (=permissive)    File-lookup policy (see --supported-policies)
  --lookup-path arg (=FHICL_FILE_PATH) path or environment variable to be used 
                                       by lookup-policy
  --supported-types                    list the C++ types supported for by the 
                                       --atom-as and --sequence-of options.
  --supported-policies                 list the supported file lookup policies

Note that bash completions of the program options will be enabled upon setting up the fhiclcpp UPS product.

Supported C++ types¶

To determine which types can be used for the --atom-as or --sequence-of program options, the user may type:

$ fhicl-get --supported-types 

For the following command line:

  fhicl-get --atom-as=T <key> <file>

the <file> is queried for the <key>, and an attempt is made to
interpret the corresponding value as an object of type T.

If instead the command line were specified as:

  fhicl-get --sequence-of=T <key> <file>

then the value corresponding to <key> would be interpreted as an
std::vector<T> object.

For either the --atom-as or --sequence-of program options, an
exception will be thrown if the <key> parameter does not exist in the
<file>, or if the parameter does not correspond to a value that can be
interpreted according to the user-specified command-line.

Supported types include:
  'double'
  'int'
  'string'

Use cases¶

For the configuration:

# test.fcl
globe_facts: {
  NumContinents: 7
  Bulgaria: country
  London: city
}
explorers: ["da Gama", Columbus, Magellan]

we get the following queries:

$ fhicl-get --atom-as=string globe_facts.Bulgaria test.fcl
country

$ fhicl-get --atom-as=int globe_facts.NumContinents test.fcl
7

$ fhicl-get --names-in globe_facts test.fcl
Bulgaria
London
NumContinents

$ fhicl-get --sequence-of=string explorers test.fcl
da Gama
Columbus
Magellan

Please let us know if this interface does not meet your needs.