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diff --git a/doc/sphinx/language/core/basic.rst b/doc/sphinx/language/core/basic.rst new file mode 100644 index 0000000000..03da59e0bf --- /dev/null +++ b/doc/sphinx/language/core/basic.rst @@ -0,0 +1,262 @@ +.. _lexical-conventions: + +Lexical conventions +=================== + +Blanks + Space, newline and horizontal tab are considered blanks. + Blanks are ignored but they separate tokens. + +Comments + Comments are enclosed between ``(*`` and ``*)``. They can be nested. + They can contain any character. However, embedded :n:`@string` literals must be + correctly closed. Comments are treated as blanks. + +Identifiers + Identifiers, written :n:`@ident`, are sequences of letters, digits, ``_`` and + ``'``, that do not start with a digit or ``'``. That is, they are + recognized by the following grammar (except that the string ``_`` is reserved; + it is not a valid identifier): + + .. insertprodn ident subsequent_letter + + .. prodn:: + ident ::= @first_letter {* @subsequent_letter } + first_letter ::= {| a .. z | A .. Z | _ | @unicode_letter } + subsequent_letter ::= {| @first_letter | @digit | ' | @unicode_id_part } + + All characters are meaningful. In particular, identifiers are case-sensitive. + :production:`unicode_letter` non-exhaustively includes Latin, + Greek, Gothic, Cyrillic, Arabic, Hebrew, Georgian, Hangul, Hiragana + and Katakana characters, CJK ideographs, mathematical letter-like + symbols and non-breaking space. :production:`unicode_id_part` + non-exhaustively includes symbols for prime letters and subscripts. + +Numerals + Numerals are sequences of digits with an optional fractional part + and exponent, optionally preceded by a minus sign. :n:`@int` is an integer; + a numeral without fractional or exponent parts. :n:`@num` is a non-negative + integer. Underscores embedded in the digits are ignored, for example + ``1_000_000`` is the same as ``1000000``. + + .. insertprodn numeral digit + + .. prodn:: + numeral ::= {+ @digit } {? . {+ @digit } } {? {| e | E } {? {| + | - } } {+ @digit } } + int ::= {? - } {+ @digit } + num ::= {+ @digit } + digit ::= 0 .. 9 + +Strings + Strings begin and end with ``"`` (double quote). Use ``""`` to represent + a double quote character within a string. In the grammar, strings are + identified with :production:`string`. + +Keywords + The following character sequences are reserved keywords that cannot be + used as identifiers:: + + _ Axiom CoFixpoint Definition Fixpoint Hypothesis IF Parameter Prop + SProp Set Theorem Type Variable as at by cofix discriminated else + end exists exists2 fix for forall fun if in lazymatch let match + multimatch return then using where with + + Note that plugins may define additional keywords when they are loaded. + +Other tokens + The set of + tokens defined at any given time can vary because the :cmd:`Notation` + command can define new tokens. A :cmd:`Require` command may load more notation definitions, + while the end of a :cmd:`Section` may remove notations. Some notations + are defined in the basic library (see :ref:`thecoqlibrary`) and are normally + loaded automatically at startup time. + + Here are the character sequences that Coq directly defines as tokens + without using :cmd:`Notation` (omitting 25 specialized tokens that begin with + ``#int63_``):: + + ! #[ % & ' ( () (bfs) (dfs) ) * ** + , - -> + . .( .. ... / : ::= := :> :>> ; < <+ <- <: + <<: <= = => > >-> >= ? @ @{ [ [= ] _ + `( `{ { {| | |- || } + + When multiple tokens match the beginning of a sequence of characters, + the longest matching token is used. + Occasionally you may need to insert spaces to separate tokens. For example, + if ``~`` and ``~~`` are both defined as tokens, the inputs ``~ ~`` and + ``~~`` generate different tokens, whereas if `~~` is not defined, then the + two inputs are equivalent. + +.. _gallina-attributes: + +Attributes +----------- + +.. insertprodn all_attrs legacy_attr + +.. prodn:: + all_attrs ::= {* #[ {*, @attr } ] } {* @legacy_attr } + attr ::= @ident {? @attr_value } + attr_value ::= = @string + | ( {*, @attr } ) + legacy_attr ::= {| Local | Global } + | {| Polymorphic | Monomorphic } + | {| Cumulative | NonCumulative } + | Private + | Program + +Attributes modify the behavior of a command or tactic. +Syntactically, most commands and tactics can be decorated with attributes, but +attributes not supported by the command or tactic will be flagged as errors. + +The order of top-level attributes doesn't affect their meaning. ``#[foo,bar]``, ``#[bar,foo]``, +``#[foo]#[bar]`` and ``#[bar]#[foo]`` are equivalent. + +The legacy attributes (:n:`@legacy_attr`) provide an older, alternate syntax +for certain attributes. They are equivalent to new attributes as follows: + +================ ================================ +Legacy attribute New attribute +================ ================================ +`Local` :attr:`local` +`Global` :attr:`global` +`Polymorphic` :attr:`universes(polymorphic)` +`Monomorphic` :attr:`universes(monomorphic)` +`Cumulative` :attr:`universes(cumulative)` +`NonCumulative` :attr:`universes(noncumulative)` +`Private` :attr:`private(matching)` +`Program` :attr:`program` +================ ================================ + +.. warn:: Unsupported attribute + + This warning is an error by default. It is caused by using a + command with some attribute it does not understand. + +.. _flags-options-tables: + +Flags, Options and Tables +----------------------------- + +Coq has many settings to control its behavior. Setting types include flags, options +and tables: + +* A *flag* has a boolean value, such as :flag:`Asymmetric Patterns`. +* An *option* generally has a numeric or string value, such as :opt:`Firstorder Depth`. +* A *table* contains a set of strings or qualids. +* In addition, some commands provide settings, such as :cmd:`Extraction Language`. + +.. FIXME Convert "Extraction Language" to an option. + +Flags, options and tables are identified by a series of identifiers, each with an initial +capital letter. + +.. cmd:: Set @setting_name {? {| @int | @string } } + :name: Set + + .. insertprodn setting_name setting_name + + .. prodn:: + setting_name ::= {+ @ident } + + If :n:`@setting_name` is a flag, no value may be provided; the flag + is set to on. + If :n:`@setting_name` is an option, a value of the appropriate type + must be provided; the option is set to the specified value. + + This command supports the :attr:`local`, :attr:`global` and :attr:`export` attributes. + They are described :ref:`here <set_unset_scope_qualifiers>`. + + .. warn:: There is no flag or option with this name: "@setting_name". + + This warning message can be raised by :cmd:`Set` and + :cmd:`Unset` when :n:`@setting_name` is unknown. It is a + warning rather than an error because this helps library authors + produce Coq code that is compatible with several Coq versions. + To preserve the same behavior, they may need to set some + compatibility flags or options that did not exist in previous + Coq versions. + +.. cmd:: Unset @setting_name + :name: Unset + + If :n:`@setting_name` is a flag, it is set to off. If :n:`@setting_name` is an option, it is + set to its default value. + + This command supports the :attr:`local`, :attr:`global` and :attr:`export` attributes. + They are described :ref:`here <set_unset_scope_qualifiers>`. + +.. cmd:: Add @setting_name {+ {| @qualid | @string } } + + Adds the specified values to the table :n:`@setting_name`. + +.. cmd:: Remove @setting_name {+ {| @qualid | @string } } + + Removes the specified value from the table :n:`@setting_name`. + +.. cmd:: Test @setting_name {? for {+ {| @qualid | @string } } } + + If :n:`@setting_name` is a flag or option, prints its current value. + If :n:`@setting_name` is a table: if the `for` clause is specified, reports + whether the table contains each specified value, otherise this is equivalent to + :cmd:`Print Table`. The `for` clause is not valid for flags and options. + + .. exn:: There is no flag, option or table with this name: "@setting_name". + + This error message is raised when calling the :cmd:`Test` + command (without the `for` clause), or the :cmd:`Print Table` + command, for an unknown :n:`@setting_name`. + + .. exn:: There is no qualid-valued table with this name: "@setting_name". + There is no string-valued table with this name: "@setting_name". + + These error messages are raised when calling the :cmd:`Add` or + :cmd:`Remove` commands, or the :cmd:`Test` command with the + `for` clause, if :n:`@setting_name` is unknown or does not have + the right type. + +.. cmd:: Print Options + + Prints the current value of all flags and options, and the names of all tables. + +.. cmd:: Print Table @setting_name + + Prints the values in the table :n:`@setting_name`. + +.. cmd:: Print Tables + + A synonym for :cmd:`Print Options`. + +.. _set_unset_scope_qualifiers: + +Locality attributes supported by :cmd:`Set` and :cmd:`Unset` +```````````````````````````````````````````````````````````` + +The :cmd:`Set` and :cmd:`Unset` commands support the :attr:`local`, +:attr:`global` and :attr:`export` locality attributes: + +* no attribute: the original setting is *not* restored at the end of + the current module or section. +* :attr:`local` (an alternative syntax is to use the ``Local`` + prefix): the setting is applied within the current module or + section. The original value of the setting is restored at the end + of the current module or section. +* :attr:`export` (an alternative syntax is to use the ``Export`` + prefix): similar to :attr:`local`, the original value of the setting + is restored at the end of the current module or section. In + addition, if the value is set in a module, then :cmd:`Import`\-ing + the module sets the option or flag. +* :attr:`global` (an alternative syntax is to use the ``Global`` + prefix): the original setting is *not* restored at the end of the + current module or section. In addition, if the value is set in a + file, then :cmd:`Require`\-ing the file sets the option. + +Newly opened modules and sections inherit the current settings. + +.. note:: + + The use of the :attr:`global` attribute with the :cmd:`Set` and + :cmd:`Unset` commands is discouraged. If your goal is to define + project-wide settings, you should rather use the command-line + arguments ``-set`` and ``-unset`` for setting flags and options + (cf. :ref:`command-line-options`). |