Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from http://docs.racket-lang.org/reference/stxcmp.html below:

12.3 Syntax Object Bindings

Returns

if the identifier

would bind

(or vice versa) if the identifiers were substituted in a suitable expression context at the

indicated by

,

otherwise. A

value for

corresponds to the

.

Examples:

> (check a a)

'binds

> (check a b)

'no-binds

> (define-syntax-rule (check-a x) (check a x)) > (check-a a)

'no-binds

“Same module binding” means that the identifiers refer to the same original definition site, and not necessarily to the same require or provide site. Due to renaming in require and provide, or due to a transformer binding to a rename transformer, the identifiers may return distinct results with syntax-e.

Examples:

> (check car)

'(same: #<procedure:car>)

> (check mcar)

'(different: #<procedure:mcar>)

'(different: #<procedure:list>)

> (require (rename-in racket/base [car kar])) > (check kar)

'(same: #<procedure:car>)

Compares each identifier in

with every other identifier in the list with

. If any comparison returns

, one of the duplicate identifiers is returned (the first one in

that is a duplicate), otherwise the result is

.

Returns one of three (if

is

) or four (if

is true) kinds of values, depending on the binding of

at the

indicated by

(where a

value for

corresponds to the

):

• The result is 'lexical if id-stx has a local binding.

• The result is a list of seven items when id-stx has a module binding: (list from-mod from-sym nominal-from-mod nominal-from-sym from-phase import-phase+space-shift nominal-export-phase).

  • from-mod is a module path index (see Compiled Modules and References) that indicates the defining module. It is the “self” module path index if the binding refers to a definition in the enclosing module of id-stx.

  • from-sym is a symbol for the identifier’s name at its definition site in the originating module. This can be different from the local name returned by syntax->datum for several reasons: the identifier is renamed on import, it is renamed on export, or it is implicitly renamed because the binding site was generated by a macro invocation. In that last case, it may be an unreadable symbol, and it may be different from the result of syntax->datum on the identifier in the original source definition.

  • nominal-from-mod is a module path index (see Compiled Modules and References) that indicates the binding’s module as it appears locally in the source around id-stx: it indicates a module required into the context of id-stx to provide its binding, or it is the same “self” as from-mod for a binding that refers to a definition in the enclosing module of id-stx. It can be different from from-mod due to a re-export in nominal-from-mod of some imported identifier. If the same binding is imported in multiple ways, an arbitrary representative is chosen.

  • nominal-from-sym is a symbol for the binding’s identifier as it appears locally in the source around id-stx: it is the identifier’s name as exported by nominal-from-mod, or it is the source identifier’s symbol for a definition within the enclosing module of id-stx. It can be different from from-sym due to a renaming provide, even if from-mod and nominal-from-mod are the same, or due to a definition that was introduced by a macro expansion.

  • from-phase is an exact non-negative integer representing the originating phase. For example, it is 1 if the definition is for-syntax.

  • import-phase+space-shift is 0 if the binding import of nominal-from-mode is from a definition or a plain require, 1 if it is from a for-syntax import, a phase combined with a space name if it is from a for-space import, etc.

  • nominal-export-phase+space is the phase level and binding space of the export from nominal-from-mod for an imported binding, or it is the phase level of the definition for a binding from the enclosing module of id-stx.

• The result is (list top-sym) if id-stx has a top-level binding and top-level-symbol? is true. The top-sym can different from the name returned by syntax->datum when the binding definition was generated by a macro invocation.

• The result is #f if id-stx has a top-level binding and top-level-symbol? is #f or if id-stx is unbound. An unbound identifier is typically treated the same as an identifier whose top-level binding is a variable.

If id-stx is bound to a rename-transformer, the result from identifier-binding is for the identifier in the transformer, so that identifier-binding is consistent with free-identifier=?.

If exact-scopes? is a true value, then the result is #f unless the binding for id-stx has exactly the scopes of id-stx. An exact-scopes check is useful for detecting whether an identifier is already bound in a specific definition context, for example.

Changed in version 6.6.0.4 of package base: Added the top-level-symbol? argument to report information on top-level bindings.
Changed in version 8.2.0.3: Generalized phase results to phase–space combinations.
Changed in version 8.6.0.9: Added the exact-scopes? argument.

Changed in version 8.2.0.3 of package base: Generalized phase results to phase–space combinations.

Changed in version 8.2.0.3 of package base: Generalized phase results to phase–space combinations.

Changed in version 8.2.0.3 of package base: Generalized phase results to phase–space combinations.

Like

, but the result is

if the binding for

has scopes that are a subset of the scopes for

. That is, if

and

have the same symbolic name, a binding for

is returned only if the binding does not also apply to

.

Added in version 8.3.0.8 of package base.
Changed in version 8.8.0.2: Added the top-level-symbol? argument.

Like

, but produces a symbol that corresponds to the binding. The symbol result is the same for any identifiers that are

, but the result may also be the same for identifiers that are not

(i.e., different symbols imply different bindings, but the same symbol does not imply the same binding).

When identifier-binding would produce a list, then the second element of that list is the result that identifier-binding-symbol produces.

Added in version 8.3.0.8 of package base.

  stx : stx?   exact-scopes? : any/c = #f

Returns a list of all

symbols for which

would produce a non-

value. This procedure takes time proportional to the number of scopes on

plus the length of the result list.

Added in version 8.6.0.6 of package base.
Changed in version 8.6.0.9: Added the exact-scopes? argument.

Added in version 8.13.0.8 of package base.

Returns a list that includes all

s for which

might produce a non-empty list.

Examples:

Added in version 8.6.0.8 of package base.

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4