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diff --git a/doc/namespace.n b/doc/namespace.n deleted file mode 100644 index eeb45f5..0000000 --- a/doc/namespace.n +++ /dev/null @@ -1,563 +0,0 @@ -'\" -'\" Copyright (c) 1993-1997 Bell Labs Innovations for Lucent Technologies -'\" Copyright (c) 1997 Sun Microsystems, Inc. -'\" -'\" See the file "license.terms" for information on usage and redistribution -'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. -'\" -'\" RCS: @(#) $Id: namespace.n,v 1.3 1999/04/16 00:46:35 stanton Exp $ -'\" -.so man.macros -.TH namespace n 8.0 Tcl "Tcl Built-In Commands" -.BS -'\" Note: do not modify the .SH NAME line immediately below! -.SH NAME -namespace \- create and manipulate contexts for commands and variables -.SH SYNOPSIS -\fBnamespace \fR?\fIoption\fR? ?\fIarg ...\fR? -.BE - -.SH DESCRIPTION -.PP -The \fBnamespace\fR command lets you create, access, and destroy -separate contexts for commands and variables. -See the section \fBWHAT IS A NAMESPACE?\fR below -for a brief overview of namespaces. -The legal \fIoption\fR's are listed below. -Note that you can abbreviate the \fIoption\fR's. -.TP -\fBnamespace children \fR?\fInamespace\fR? ?\fIpattern\fR? -Returns a list of all child namespaces that belong to the -namespace \fInamespace\fR. -If \fInamespace\fR is not specified, -then the children are returned for the current namespace. -This command returns fully-qualified names, -which start with \fB::\fR. -If the optional \fIpattern\fR is given, -then this command returns only the names that match the glob-style pattern. -The actual pattern used is determined as follows: -a pattern that starts with \fB::\fR is used directly, -otherwise the namespace \fInamespace\fR -(or the fully-qualified name of the current namespace) -is prepended onto the the pattern. -.TP -\fBnamespace code \fIscript\fR -Captures the current namespace context for later execution -of the script \fIscript\fR. -It returns a new script in which \fIscript\fR has been wrapped -in a \fBnamespace code\fR command. -The new script has two important properties. -First, it can be evaluated in any namespace and will cause -\fIscript\fR to be evaluated in the current namespace -(the one where the \fBnamespace code\fR command was invoked). -Second, additional arguments can be appended to the resulting script -and they will be passed to \fIscript\fR as additional arguments. -For example, suppose the command -\fBset script [namespace code {foo bar}]\fR -is invoked in namespace \fB::a::b\fR. -Then \fBeval "$script x y"\fR -can be executed in any namespace (assuming the value of -\fBscript\fR has been passed in properly) -and will have the same effect as the command -\fBnamespace eval ::a::b {foo bar x y}\fR. -This command is needed because -extensions like Tk normally execute callback scripts -in the global namespace. -A scoped command captures a command together with its namespace context -in a way that allows it to be executed properly later. -See the section \fBSCOPED VALUES\fR for some examples -of how this is used to create callback scripts. -.TP -\fBnamespace current\fR -Returns the fully-qualified name for the current namespace. -The actual name of the global namespace is ``'' -(i.e., an empty string), -but this command returns \fB::\fR for the global namespace -as a convenience to programmers. -.TP -\fBnamespace delete \fR?\fInamespace namespace ...\fR? -Each namespace \fInamespace\fR is deleted -and all variables, procedures, and child namespaces -contained in the namespace are deleted. -If a procedure is currently executing inside the namespace, -the namespace will be kept alive until the procedure returns; -however, the namespace is marked to prevent other code from -looking it up by name. -If a namespace doesn't exist, this command returns an error. -If no namespace names are given, this command does nothing. -.TP -\fBnamespace eval\fR \fInamespace arg\fR ?\fIarg ...\fR? -Activates a namespace called \fInamespace\fR and evaluates some code -in that context. -If the namespace does not already exist, it is created. -If more than one \fIarg\fR argument is specified, -the arguments are concatenated together with a space between each one -in the same fashion as the \fBeval\fR command, -and the result is evaluated. -.br -.sp -If \fInamespace\fR has leading namespace qualifiers -and any leading namespaces do not exist, -they are automatically created. -.TP -\fBnamespace export \fR?\-\fBclear\fR? ?\fIpattern pattern ...\fR? -Specifies which commands are exported from a namespace. -The exported commands are those that can be later imported -into another namespace using a \fBnamespace import\fR command. -Both commands defined in a namespace and -commands the namespace has previously imported -can be exported by a namespace. -The commands do not have to be defined -at the time the \fBnamespace export\fR command is executed. -Each \fIpattern\fR may contain glob-style special characters, -but it may not include any namespace qualifiers. -That is, the pattern can only specify commands -in the current (exporting) namespace. -Each \fIpattern\fR is appended onto the namespace's list of export patterns. -If the \-\fBclear\fR flag is given, -the namespace's export pattern list is reset to empty before any -\fIpattern\fR arguments are appended. -If no \fIpattern\fRs are given and the \-\fBclear\fR flag isn't given, -this command returns the namespace's current export list. -.TP -\fBnamespace forget \fR?\fIpattern pattern ...\fR? -Removes previously imported commands from a namespace. -Each \fIpattern\fR is a qualified name such as -\fBfoo::x\fR or \fBa::b::p*\fR. -Qualified names contain \fB::\fRs and qualify a name -with the name of one or more namespaces. -Each \fIpattern\fR is qualified with the name of an exporting namespace -and may have glob-style special characters in the command name -at the end of the qualified name. -Glob characters may not appear in a namespace name. -This command first finds the matching exported commands. -It then checks whether any of those those commands -were previously imported by the current namespace. -If so, this command deletes the corresponding imported commands. -In effect, this un-does the action of a \fBnamespace import\fR command. -.TP -\fBnamespace import \fR?\fB\-force\fR? ?\fIpattern\fR \fIpattern ...\fR? -Imports commands into a namespace. -Each \fIpattern\fR is a qualified name like -\fBfoo::x\fR or \fBa::p*\fR. -That is, it includes the name of an exporting namespace -and may have glob-style special characters in the command name -at the end of the qualified name. -Glob characters may not appear in a namespace name. -All the commands that match a \fIpattern\fR string -and which are currently exported from their namespace -are added to the current namespace. -This is done by creating a new command in the current namespace -that points to the exported command in its original namespace; -when the new imported command is called, it invokes the exported command. -This command normally returns an error -if an imported command conflicts with an existing command. -However, if the \-\fBforce\fR option is given, -imported commands will silently replace existing commands. -The \fBnamespace import\fR command has snapshot semantics: -that is, only requested commands that are currently defined -in the exporting namespace are imported. -In other words, you can import only the commands that are in a namespace -at the time when the \fBnamespace import\fR command is executed. -If another command is defined and exported in this namespace later on, -it will not be imported. -.TP -\fBnamespace inscope\fR \fInamespace arg\fR ?\fIarg ...\fR? -Executes a script in the context of a particular namespace. -This command is not expected to be used directly by programmers; -calls to it are generated implicitly when applications -use \fBnamespace code\fR commands to create callback scripts -that the applications then register with, e.g., Tk widgets. -The \fBnamespace inscope\fR command is much like the \fBnamespace eval\fR -command except that it has \fBlappend\fR semantics -and the namespace must already exist. -It treats the first argument as a list, -and appends any arguments after the first -onto the end as proper list elements. -\fBnamespace inscope ::foo a x y z\fR -is equivalent to -\fBnamespace eval ::foo [concat a [list x y z]]\fR -This \fBlappend\fR semantics is important because many callback scripts -are actually prefixes. -.TP -\fBnamespace origin \fIcommand\fR -Returns the fully-qualified name of the original command -to which the imported command \fIcommand\fR refers. -When a command is imported into a namespace, -a new command is created in that namespace -that points to the actual command in the exporting namespace. -If a command is imported into a sequence of namespaces -\fIa, b,...,n\fR where each successive namespace -just imports the command from the previous namespace, -this command returns the fully-qualified name of the original command -in the first namespace, \fIa\fR. -If \fIcommand\fR does not refer to an imported command, -the command's own fully-qualified name is returned. -.TP -\fBnamespace parent\fR ?\fInamespace\fR? -Returns the fully-qualified name of the parent namespace -for namespace \fInamespace\fR. -If \fInamespace\fR is not specified, -the fully-qualified name of the current namespace's parent is returned. -.TP -\fBnamespace qualifiers\fR \fIstring\fR -Returns any leading namespace qualifiers for \fIstring\fR. -Qualifiers are namespace names separated by \fB::\fRs. -For the \fIstring\fR \fB::foo::bar::x\fR, -this command returns \fB::foo::bar\fR, -and for \fB::\fR it returns \fB``''\fR (an empty string). -This command is the complement of the \fBnamespace tail\fR command. -Note that it does not check whether the -namespace names are, in fact, -the names of currently defined namespaces. -.TP -\fBnamespace tail\fR \fIstring\fR -Returns the simple name at the end of a qualified string. -Qualifiers are namespace names separated by \fB::\fRs. -For the \fIstring\fR \fB::foo::bar::x\fR, -this command returns \fBx\fR, -and for \fB::\fR it returns \fB``''\fR (an empty string). -This command is the complement of the \fBnamespace qualifiers\fR command. -It does not check whether the namespace names are, in fact, -the names of currently defined namespaces. -.TP -\fBnamespace which\fR ?\-\fBcommand\fR? ?\-\fBvariable\fR? \fIname\fR -Looks up \fIname\fR as either a command or variable -and returns its fully-qualified name. -For example, if \fIname\fR does not exist in the current namespace -but does exist in the global namespace, -this command returns a fully-qualified name in the global namespace. -If the command or variable does not exist, -this command returns an empty string. -If no flag is given, \fIname\fR is treated as a command name. -See the section \fBNAME RESOLUTION\fR below for an explanation of -the rules regarding name resolution. - -.SH "WHAT IS A NAMESPACE?" -.PP -A namespace is a collection of commands and variables. -It encapsulates the commands and variables to ensure that they -won't interfere with the commands and variables of other namespaces. -Tcl has always had one such collection, -which we refer to as the \fIglobal namespace\fR. -The global namespace holds all global variables and commands. -The \fBnamespace eval\fR command lets you create new namespaces. -For example, -.CS -\fBnamespace eval Counter { - namespace export bump - variable num 0 - - proc bump {} { - variable num - incr num - } -}\fR -.CE -creates a new namespace containing the variable \fBnum\fR and -the procedure \fBbump\fR. -The commands and variables in this namespace are separate from -other commands and variables in the same program. -If there is a command named \fBbump\fR in the global namespace, -for example, it will be different from the command \fBbump\fR -in the \fBCounter\fR namespace. -.PP -Namespace variables resemble global variables in Tcl. -They exist outside of the procedures in a namespace -but can be accessed in a procedure via the \fBvariable\fR command, -as shown in the example above. -.PP -Namespaces are dynamic. -You can add and delete commands and variables at any time, -so you can build up the contents of a -namespace over time using a series of \fBnamespace eval\fR commands. -For example, the following series of commands has the same effect -as the namespace definition shown above: -.CS -\fBnamespace eval Counter { - variable num 0 - proc bump {} { - variable num - return [incr num] - } -} -namespace eval Counter { - proc test {args} { - return $args - } -} -namespace eval Counter { - rename test "" -}\fR -.CE -Note that the \fBtest\fR procedure is added to the \fBCounter\fR namespace, -and later removed via the \fBrename\fR command. -.PP -Namespaces can have other namespaces within them, -so they nest hierarchically. -A nested namespace is encapsulated inside its parent namespace -and can not interfere with other namespaces. - -.SH "QUALIFIED NAMES" -.PP -Each namespace has a textual name such as -\fBhistory\fR or \fB::safe::interp\fR. -Since namespaces may nest, -qualified names are used to refer to -commands, variables, and child namespaces contained inside namespaces. -Qualified names are similar to the hierarchical path names for -Unix files or Tk widgets, -except that \fB::\fR is used as the separator -instead of \fB/\fR or \fB.\fR. -The topmost or global namespace has the name ``'' (i.e., an empty string), -although \fB::\fR is a synonym. -As an example, the name \fB::safe::interp::create\fR -refers to the command \fBcreate\fR in the namespace \fBinterp\fR -that is a child of of namespace \fB::safe\fR, -which in turn is a child of the global namespace \fB::\fR. -.PP -If you want to access commands and variables from another namespace, -you must use some extra syntax. -Names must be qualified by the namespace that contains them. -From the global namespace, -we might access the \fBCounter\fR procedures like this: -.CS -\fBCounter::bump 5 -Counter::Reset\fR -.CE -We could access the current count like this: -.CS -\fBputs "count = $Counter::num"\fR -.CE -When one namespace contains another, you may need more than one -qualifier to reach its elements. -If we had a namespace \fBFoo\fR that contained the namespace \fBCounter\fR, -you could invoke its \fBbump\fR procedure -from the global namespace like this: -.CS -\fBFoo::Counter::bump 3\fR -.CE -.PP -You can also use qualified names when you create and rename commands. -For example, you could add a procedure to the \fBFoo\fR -namespace like this: -.CS -\fBproc Foo::Test {args} {return $args}\fR -.CE -And you could move the same procedure to another namespace like this: -.CS -\fBrename Foo::Test Bar::Test\fR -.CE -.PP -There are a few remaining points about qualified names -that we should cover. -Namespaces have nonempty names except for the global namespace. -\fB::\fR is disallowed in simple command, variable, and namespace names -except as a namespace separator. -Extra \fB:\fRs in a qualified name are ignored; -that is, two or more \fB:\fRs are treated as a namespace separator. -A trailing \fB::\fR in a qualified variable or command name -refers to the variable or command named {}. -However, a trailing \fB::\fR in a qualified namespace name is ignored. - -.SH "NAME RESOLUTION" -.PP -In general, all Tcl commands that take variable and command names -support qualified names. -This means you can give qualified names to such commands as -\fBset\fR, \fBproc\fR, \fBrename\fR, and \fBinterp alias\fR. -If you provide a fully-qualified name that starts with a \fB::\fR, -there is no question about what command, variable, or namespace -you mean. -However, if the name does not start with a \fB::\fR -(i.e., is \fIrelative\fR), -Tcl follows a fixed rule for looking it up: -Command and variable names are always resolved -by looking first in the current namespace, -and then in the global namespace. -Namespace names, on the other hand, are always resolved -by looking in only the current namespace. -.PP -In the following example, -.CS -\fBset traceLevel 0 -namespace eval Debug { - printTrace $traceLevel -}\fR -.CE -Tcl looks for \fBtraceLevel\fR in the namespace \fBDebug\fR -and then in the global namespace. -It looks up the command \fBprintTrace\fR in the same way. -If a variable or command name is not found in either context, -the name is undefined. -To make this point absolutely clear, consider the following example: -.CS -\fBset traceLevel 0 -namespace eval Foo { - variable traceLevel 3 - - namespace eval Debug { - printTrace $traceLevel - } -}\fR -.CE -Here Tcl looks for \fBtraceLevel\fR first in the namespace \fBFoo::Debug\fR. -Since it is not found there, Tcl then looks for it -in the global namespace. -The variable \fBFoo::traceLevel\fR is completely ignored -during the name resolution process. -.PP -You can use the \fBnamespace which\fR command to clear up any question -about name resolution. -For example, the command: -.CS -\fBnamespace eval Foo::Debug {namespace which \-variable traceLevel}\fR -.CE -returns \fB::traceLevel\fR. -On the other hand, the command, -.CS -\fBnamespace eval Foo {namespace which \-variable traceLevel}\fR -.CE -returns \fB::Foo::traceLevel\fR. -.PP -As mentioned above, -namespace names are looked up differently -than the names of variables and commands. -Namespace names are always resolved in the current namespace. -This means, for example, -that a \fBnamespace eval\fR command that creates a new namespace -always creates a child of the current namespace -unless the new namespace name begins with a \fB::\fR. -.PP -Tcl has no access control to limit what variables, commands, -or namespaces you can reference. -If you provide a qualified name that resolves to an element -by the name resolution rule above, -you can access the element. -.PP -You can access a namespace variable -from a procedure in the same namespace -by using the \fBvariable\fR command. -Much like the \fBglobal\fR command, -this creates a local link to the namespace variable. -If necessary, it also creates the variable in the current namespace -and initializes it. -Note that the \fBglobal\fR command only creates links -to variables in the global namespace. -It is not necessary to use a \fBvariable\fR command -if you always refer to the namespace variable using an -appropriate qualified name. - -.SH "IMPORTING COMMANDS" -.PP -Namespaces are often used to represent libraries. -Some library commands are used so frequently -that it is a nuisance to type their qualified names. -For example, suppose that all of the commands in a package -like BLT are contained in a namespace called \fBBlt\fR. -Then you might access these commands like this: -.CS -\fBBlt::graph .g \-background red -Blt::table . .g 0,0\fR -.CE -If you use the \fBgraph\fR and \fBtable\fR commands frequently, -you may want to access them without the \fBBlt::\fR prefix. -You can do this by importing the commands into the current namespace, -like this: -.CS -\fBnamespace import Blt::*\fR -.CE -This adds all exported commands from the \fBBlt\fR namespace -into the current namespace context, so you can write code like this: -.CS -\fBgraph .g \-background red -table . .g 0,0\fR -.CE -The \fBnamespace import\fR command only imports commands -from a namespace that that namespace exported -with a \fBnamespace export\fR command. -.PP -Importing \fIevery\fR command from a namespace is generally -a bad idea since you don't know what you will get. -It is better to import just the specific commands you need. -For example, the command -.CS -\fBnamespace import Blt::graph Blt::table\fR -.CE -imports only the \fBgraph\fR and \fBtable\fR commands into the -current context. -.PP -If you try to import a command that already exists, you will get an -error. This prevents you from importing the same command from two -different packages. But from time to time (perhaps when debugging), -you may want to get around this restriction. You may want to -reissue the \fBnamespace import\fR command to pick up new commands -that have appeared in a namespace. In that case, you can use the -\fB\-force\fR option, and existing commands will be silently overwritten: -.CS -\fBnamespace import \-force Blt::graph Blt::table\fR -.CE -If for some reason, you want to stop using the imported commands, -you can remove them with an \fBnamespace forget\fR command, like this: -.CS -\fBnamespace forget Blt::*\fR -.CE -This searches the current namespace for any commands imported from \fBBlt\fR. -If it finds any, it removes them. Otherwise, it does nothing. -After this, the \fBBlt\fR commands must be accessed with the \fBBlt::\fR -prefix. -.PP -When you delete a command from the exporting namespace like this: -.CS -\fBrename Blt::graph ""\fR -.CE -the command is automatically removed from all namespaces that import it. - -.SH "EXPORTING COMMANDS" -You can export commands from a namespace like this: -.CS -\fBnamespace eval Counter { - namespace export bump reset - variable Num 0 - variable Max 100 - - proc bump {{by 1}} { - variable Num - incr Num $by - Check - return $Num - } - proc reset {} { - variable Num - set Num 0 - } - proc Check {} { - variable Num - variable Max - if {$Num > $Max} { - error "too high!" - } - } -}\fR -.CE -The procedures \fBbump\fR and \fBreset\fR are exported, -so they are included when you import from the \fBCounter\fR namespace, -like this: -.CS -\fBnamespace import Counter::*\fR -.CE -However, the \fBCheck\fR procedure is not exported, -so it is ignored by the import operation. -.PP -The \fBnamespace import\fR command only imports commands -that were declared as exported by their namespace. -The \fBnamespace export\fR command specifies what commands -may be imported by other namespaces. -If a \fBnamespace import\fR command specifies a command -that is not exported, the command is not imported. - -.SH "SEE ALSO" -variable(n) - -.SH KEYWORDS -exported, internal, variable |