Tcl_Ensemble(3) Tcl Library Procedures Tcl_Ensemble(3)

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NAME

Tcl_CreateEnsemble, Tcl_FindEnsemble, Tcl_GetEnsembleFlags,
Tcl_GetEnsembleMappingDict, Tcl_GetEnsembleNamespace,
Tcl_GetEnsembleParameterList, Tcl_GetEnsembleUnknownHandler,
Tcl_GetEnsembleSubcommandList, Tcl_IsEnsemble, Tcl_SetEnsembleFlags,
Tcl_SetEnsembleMappingDict, 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
messages are written.
The functions whose
names start with
Tcl_GetEnsemble 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 OR'ed set of flag
bits describing the
basic configuration of
the ensemble. Currently
only one bit has
meaning,
TCL_ENSEMBLE_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 OR'ed set of flag
bits controlling the
behavior of
Tcl_FindEnsemble.
Currently only
TCL_LEAVE_ERR_MSG is
supported.

Tcl_Command token (in) A normal command token
that refers to an
ensemble 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 implementation
command prefix 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
subcommands in the
dictionary or the
unknown subcommand
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
parameters, the defined
list of subcommands or
the current unknown
handler prefix.

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
arguments: the interpreter to work within, the name of the ensemble
to create, 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
cmdNameObj) does not refer to an ensemble command, the result of the
function is NULL and (if the TCL_LEAVE_ERR_MSG bit is set in flags)
an error 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 token 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
ensemble's bound namespace. Defaults to NULL. May be read and
written using Tcl_GetEnsembleMappingDict and
Tcl_SetEnsembleMappingDict 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 |
ensemble between the name of the ensemble and the subcommand |
argument. 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 |
obtained 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
dictionary (see above) or (if that is also NULL) from the set
of commands exported by the bound namespace. May be read and
written using Tcl_GetEnsembleSubcommandList and
Tcl_SetEnsembleSubcommandList 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_GetEnsembleSubcommandList 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
current 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_GetEnsembleUnknownHandler 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 refer to an
ensemble).

SEE ALSO

namespace(n), Tcl_DeleteCommandFromToken(3)

KEYWORDS

command, ensemble

Tcl 8.5 Tcl_Ensemble(3)