Program state

### 7.23 Program state

- `consult/1`, `’.’/2` - program consult
- `load/1`
- `listing/1`, `listing/0`

#### 7.23.1 `consult/1`, `’.’/2` - program consult

Templates

  `consult(+atom_or_atom_list)
  ’.’(+atom, +atom_list)`

Description

`consult(Files)` compiles and loads into memory each file of the list `Files`. Each file is compiled for byte-code using the GNU Prolog compiler (section 3.4) then loaded using `load/1` (section 7.23.2). It is possible to specify `user` as a file name to directly enter the program from the terminal. `Files` can be also a single file name (i.e. an atom). Refer to the section concerning the consult of a Prolog program for more information (section 3.2.3).

The final file name of a file is computed using the predicates `prolog_file_name/2` (section 7.26.3) and `absolute_file_name/2` (section 7.26.1).

`[ File | Files ]`, i.e. `’.’(File, Files)` is equivalent to `consult([ File | Files ])`.

Errors

`Files` is a partial list or a list with an element `E` which is a variable |  | `instantiation_error`
`Files` is neither a partial list nor a list nor an atom |  | `type_error(list, Files)`
an element `E` of the `Files` list is neither a variable nor an atom |  | `type_error(atom, E)`
an element `E` of the `Files` list is an atom but not a valid pathname |  | `domain_error(os_path, E)`
an element `E` of the `Files` list is a valid pathname but does not correspond to an existing source |  | `existence_error(source_sink, E)`
an error occurs executing a directive |  | see `call/1` errors (section 6.2.3)

Portability

GNU Prolog predicates.

#### 7.23.2 `load/1`

Templates

  `load(+atom_or_atom_list)`

Description

`load(Files)` loads into memory each file of the list `Files`. Each file must have been previously compiled for byte-code using the GNU Prolog compiler (section 3.4). `Files` can be also a single file name (i.e. an atom).

The final file name of a file is computed using the predicates `absolute_file_name/2` (section 7.26.1). If no suffix is given `’.wbc’` is appended to the file name.

Errors

`Files` is a partial list or a list with an element `E` which is a variable |  | `instantiation_error`
`Files` is neither a partial list nor a list nor an atom |  | `type_error(list, Files)`
an element `E` of the `Files` list is neither a variable nor an atom |  | `type_error(atom, E)`
an element `E` of the `Files` list is an atom but not a valid pathname |  | `domain_error(os_path, E)`
an element `E` of the `Files` list is a valid pathname but does not correspond to an existing source |  | `existence_error(source_sink, E)`
an error occurs executing a directive |  | see `call/1` errors (section 6.2.3)

Portability

GNU Prolog predicate.

#### 7.23.3 `listing/1`, `listing/0`

Templates

  `listing(+predicate_indicator)
  listing(+atom)
  listing`

Description

`listing(Pred)` lists the clauses of the consulted predicate whose predicate indicator is `Pred`. `Pred` can also be a single atom in which case all predicates whose name is `Pred` are listed (of any arity). This predicate uses `portray_clause/2` (section 7.14.8) to output the clauses.

`listing` lists all clauses of all consulted predicates.

Errors

`Pred` is a variable |  | `instantiation_error`
`Pred` is neither a variable nor predicate indicator or an atom |  | `type_error(predicate_indicator, Pred)`

Portability

GNU Prolog predicate.

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