Tcl_Ensemble(3tcl) Tcl Library Procedures Tcl_Ensemble(3tcl)
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NAME
Tcl_CreateEnsemble, Tcl_FindEnsemble, Tcl_GetEnsembleFlags,
Tcl_GetEnsembleMappingDict, Tcl_GetEnsembleNamespace, Tcl_GetEnsem-
bleParameterList, Tcl_GetEnsembleUnknownHandler, Tcl_GetEnsembleSubcom-
mandList, Tcl_IsEnsemble, Tcl_SetEnsembleFlags, Tcl_SetEnsembleMapping-
Dict, Tcl_SetEnsembleParameterList, Tcl_SetEnsembleSubcommandList,
Tcl_SetEnsembleUnknownHandler - manipulate ensemble commands
SYNOPSIS
#include <tcl.h>
Tcl_Command
Tcl_CreateEnsemble(interp, name, namespacePtr, ensFlags)
Tcl_Command
Tcl_FindEnsemble(interp, cmdNameObj, flags)
int
Tcl_IsEnsemble(token)
int
Tcl_GetEnsembleFlags(interp, token, ensFlagsPtr)
int
Tcl_SetEnsembleFlags(interp, token, ensFlags)
int
Tcl_GetEnsembleMappingDict(interp, token, dictObjPtr)
int
Tcl_SetEnsembleMappingDict(interp, token, dictObj)
int │
Tcl_GetEnsembleParameterList(interp, token, listObjPtr) │
int │
Tcl_SetEnsembleParameterList(interp, token, listObj) │
int
Tcl_GetEnsembleSubcommandList(interp, token, listObjPtr)
int
Tcl_SetEnsembleSubcommandList(interp, token, listObj)
int
Tcl_GetEnsembleUnknownHandler(interp, token, listObjPtr)
int
Tcl_SetEnsembleUnknownHandler(interp, token, listObj)
int
Tcl_GetEnsembleNamespace(interp, token, namespacePtrPtr)
ARGUMENTS
Tcl_Interp *interp (in/out) The interpreter in which
the ensemble is to be
created or found. Also
where error result mes-
sages are written. The
functions whose names
start with Tcl_GetEnsem-
ble may have a NULL for
the interp, but all other
functions must not.
const char *name (in) The name of the ensemble
command to be created.
Tcl_Namespace *namespacePtr (in) The namespace to which
the ensemble command is
to be bound, or NULL for
the current namespace.
int ensFlags (in) An ORed set of flag bits
describing the basic con-
figuration of the ensem-
ble. Currently only one
bit has meaning, TCL_EN-
SEMBLE_PREFIX, which is
present when the ensemble
command should also match
unambiguous prefixes of
subcommands.
Tcl_Obj *cmdNameObj (in) A value holding the name
of the ensemble command
to look up.
int flags (in) An ORed set of flag bits
controlling the behavior
of Tcl_FindEnsemble. Cur-
rently only
TCL_LEAVE_ERR_MSG is sup-
ported.
Tcl_Command token (in) A normal command token
that refers to an ensem-
ble command, or which you
wish to use for testing
as an ensemble command in
Tcl_IsEnsemble.
int *ensFlagsPtr (out) Pointer to a variable
into which to write the
current ensemble flag
bits; currently only the
bit TCL_ENSEMBLE_PREFIX
is defined.
Tcl_Obj *dictObj (in) A dictionary value to use
for the subcommand to im-
plementation command pre-
fix mapping dictionary in
the ensemble. May be NULL
if the mapping dictionary
is to be removed.
Tcl_Obj **dictObjPtr (out) Pointer to a variable
into which to write the
current ensemble mapping
dictionary.
Tcl_Obj *listObj (in) A list value to use for
the list of formal pre-
subcommand parameters,
the defined list of sub-
commands in the dictio-
nary or the unknown sub-
command handler command
prefix. May be NULL if
the subcommand list or
unknown handler are to be
removed.
Tcl_Obj **listObjPtr (out) Pointer to a variable
into which to write the
current list of formal
pre-subcommand parame-
ters, the defined list of
subcommands or the cur-
rent unknown handler pre-
fix.
Tcl_Namespace **namespacePtrPtr (out) Pointer to a variable
into which to write the
handle of the namespace
to which the ensemble is
bound.
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DESCRIPTION
An ensemble is a command, bound to some namespace, which consists of a
collection of subcommands implemented by other Tcl commands. The first
argument to the ensemble command is always interpreted as a selector
that states what subcommand to execute.
Ensembles are created using Tcl_CreateEnsemble, which takes four argu-
ments: the interpreter to work within, the name of the ensemble to cre-
ate, the namespace within the interpreter to bind the ensemble to, and
the default set of ensemble flags. The result of the function is the
command token for the ensemble, which may be used to further configure
the ensemble using the API described below in ENSEMBLE PROPERTIES.
Given the name of an ensemble command, the token for that command may
be retrieved using Tcl_FindEnsemble. If the given command name (in cmd-
NameObj) does not refer to an ensemble command, the result of the func-
tion is NULL and (if the TCL_LEAVE_ERR_MSG bit is set in flags) an er-
ror message is left in the interpreter result.
A command token may be checked to see if it refers to an ensemble using
Tcl_IsEnsemble. This returns 1 if the token refers to an ensemble, or 0
otherwise.
ENSEMBLE PROPERTIES
Every ensemble has four read-write properties and a read-only property.
The properties are:
flags (read-write)
The set of flags for the ensemble, expressed as a bit-field.
Currently, the only public flag is TCL_ENSEMBLE_PREFIX which is
set when unambiguous prefixes of subcommands are permitted to be
resolved to implementations as well as exact matches. The flags
may be read and written using Tcl_GetEnsembleFlags and
Tcl_SetEnsembleFlags respectively. The result of both of those
functions is a Tcl result code (TCL_OK, or TCL_ERROR if the to-
ken does not refer to an ensemble).
mapping dictionary (read-write)
A dictionary containing a mapping from subcommand names to lists
of words to use as a command prefix (replacing the first two
words of the command which are the ensemble command itself and
the subcommand name), or NULL if every subcommand is to be
mapped to the command with the same unqualified name in the en-
semble's bound namespace. Defaults to NULL. May be read and
written using Tcl_GetEnsembleMappingDict and Tcl_SetEnsembleMap-
pingDict respectively. The result of both of those functions is
a Tcl result code (TCL_OK, or TCL_ERROR if the token does not
refer to an ensemble) and the dictionary obtained from
Tcl_GetEnsembleMappingDict should always be treated as immutable
even if it is unshared. All command names in prefixes set via
Tcl_SetEnsembleMappingDict must be fully qualified.
formal pre-subcommand parameter list (read-write)
A list of formal parameter names (the names only being used when │
generating error messages) that come at invocation of the ensem- │
ble between the name of the ensemble and the subcommand argu- │
ment. NULL (the default) is equivalent to the empty list. May be │
read and written using Tcl_GetEnsembleParameterList and │
Tcl_SetEnsembleParameterList respectively. The result of both of │
those functions is a Tcl result code (TCL_OK, or TCL_ERROR if │
the token does not refer to an ensemble) and the dictionary ob- │
tained from Tcl_GetEnsembleParameterList should always be │
treated as immutable even if it is unshared.
subcommand list (read-write)
A list of all the subcommand names for the ensemble, or NULL if
this is to be derived from either the keys of the mapping dic-
tionary (see above) or (if that is also NULL) from the set of
commands exported by the bound namespace. May be read and writ-
ten using Tcl_GetEnsembleSubcommandList and Tcl_SetEnsembleSub-
commandList respectively. The result of both of those functions
is a Tcl result code (TCL_OK, or TCL_ERROR if the token does not
refer to an ensemble) and the list obtained from Tcl_GetEnsem-
bleSubcommandList should always be treated as immutable even if
it is unshared.
unknown subcommand handler command prefix (read-write)
A list of words to prepend on the front of any subcommand when
the subcommand is unknown to the ensemble (according to the cur-
rent prefix handling rule); see the namespace ensemble command
for more details. If NULL, the default behavior - generate a
suitable error message - will be used when an unknown subcommand
is encountered. May be read and written using Tcl_GetEnsembleUn-
knownHandler and Tcl_SetEnsembleUnknownHandler respectively. The
result of both functions is a Tcl result code (TCL_OK, or
TCL_ERROR if the token does not refer to an ensemble) and the
list obtained from Tcl_GetEnsembleUnknownHandler should always
be treated as immutable even if it is unshared.
bound namespace (read-only)
The namespace to which the ensemble is bound; when the namespace
is deleted, so too will the ensemble, and this namespace is also
the namespace whose list of exported commands is used if both
the mapping dictionary and the subcommand list properties are
NULL. May be read using Tcl_GetEnsembleNamespace which returns a
Tcl result code (TCL_OK, or TCL_ERROR if the token does not re-
fer to an ensemble).
SEE ALSO
namespace(3tcl), Tcl_DeleteCommandFromToken(3tcl)
KEYWORDS
command, ensemble
Tcl 8.5 Tcl_Ensemble(3tcl)
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