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NAME

       dict - Manipulate dictionaries

SYNOPSIS

       dict option arg ?arg ...?
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DESCRIPTION

       Performs one of several operations on dictionary values or variables containing dictionary
       values (see the DICTIONARY VALUES section below for a description), depending  on  option.
       The legal options (which may be abbreviated) are:

       dict append dictionaryVariable key ?string ...?
              This  appends the given string (or strings) to the value that the given key maps to
              in the dictionary value contained in the  given  variable,  writing  the  resulting
              dictionary  value  back to that variable.  Non-existent keys are treated as if they
              map to an empty string.

       dict create ?key value ...?
              Create a new dictionary that contains each of  the  key/value  mappings  listed  as
              arguments  (keys  and  values  alternating,  with  each  key  being followed by its
              associated value.)

       dict exists dictionaryValue key ?key ...?
              This returns a boolean value indicating whether the given  key  (or  path  of  keys
              through  a  set  of nested dictionaries) exists in the given dictionary value. This
              returns a true value exactly when dict get on that path will succeed.

       dict filter dictionaryValue filterType arg ?arg ...?
              This takes a dictionary value and returns a new dictionary that contains just those
              key/value  pairs  that  match the specified filter type (which may be abbreviated.)
              Supported filter types are:

              dict filter dictionaryValue key globPattern
                     The key rule only matches those key/value pairs whose keys match  the  given
                     pattern (in the style of string match.)

              dict filter dictionaryValue script {keyVar valueVar} script
                     The  script  rule  tests for matching by assigning the key to the keyVar and
                     the value to the valueVar, and then evaluating the given script which should
                     return  a  boolean value (with the key/value pair only being included in the
                     result of the dict filter when a true value is  returned.)   Note  that  the
                     first  argument after the rule selection word is a two-element list.  If the
                     script returns with a condition of TCL_BREAK, no further key/value pairs are
                     considered  for  inclusion  in  the resulting dictionary, and a condition of
                     TCL_CONTINUE is equivalent to a false result. The key/value pairs are tested
                     in the order in which the keys were inserted into the dictionary.

              dict filter dictionaryValue value globPattern
                     The  value  rule  only  matches those key/value pairs whose values match the
                     given pattern (in the style of string match.)

       dict for {keyVar valueVar} dictionaryValue body
              This command takes three arguments, the first a two-element list of variable  names
              (for  the key and value respectively of each mapping in the dictionary), the second
              the dictionary value to iterate across, and the third a script to be evaluated  for
              each  mapping  with the key and value variables set appropriately (in the manner of
              foreach.)  The result of the command is an empty string. If any evaluation  of  the
              body  generates  a  TCL_BREAK  result, no further pairs from the dictionary will be
              iterated over and the dict for command will terminate successfully immediately.  If
              any  evaluation  of the body generates a TCL_CONTINUE result, this shall be treated
              exactly like a normal TCL_OK result. The order of iteration is the order  in  which
              the keys were inserted into the dictionary.

       dict get dictionaryValue ?key ...?
              Given  a  dictionary  value (first argument) and a key (second argument), this will
              retrieve the value for that key. Where several keys are supplied, the behaviour  of
              the  command  shall be as if the result of dict get $dictVal $key was passed as the
              first argument to dict get with the remaining arguments  as  second  (and  possibly
              subsequent)  arguments.  This  facilitates  lookups  in  nested  dictionaries.  For
              example, the following two commands are equivalent:

                     dict get $dict foo bar spong
                     dict get [dict get [dict get $dict foo] bar] spong

              If no keys are provided, dict get will return a list containing pairs  of  elements
              in  a manner similar to array get. That is, the first element of each pair would be
              the key and the second element would be the value for that key.

              It is an error to attempt to retrieve a value for a key that is not present in  the
              dictionary.

       dict incr dictionaryVariable key ?increment?
              This  adds  the  given  increment  value  (an  integer  that  defaults  to 1 if not
              specified) to the value that  the  given  key  maps  to  in  the  dictionary  value
              contained  in  the  given  variable, writing the resulting dictionary value back to
              that variable. Non-existent keys are treated as if they map to 0. It is an error to
              increment a value for an existing key if that value is not an integer.

       dict info dictionaryValue
              This  returns  information  (intended  for  display  to  people)  about  the  given
              dictionary though the format of this data is dependent on the implementation of the
              dictionary.  For  dictionaries  that are implemented by hash tables, it is expected
              that this will return the  string  produced  by  Tcl_HashStats,  similar  to  array
              statistics.

       dict keys dictionaryValue ?globPattern?
              Return  a list of all keys in the given dictionary value. If a pattern is supplied,
              only those keys that match it (according to the rules  of  string  match)  will  be
              returned.  The  returned keys will be in the order that they were inserted into the
              dictionary.

       dict lappend dictionaryVariable key ?value ...?
              This appends the given items to the list value that the given key maps  to  in  the
              dictionary  value contained in the given variable, writing the resulting dictionary
              value back to that variable. Non-existent keys are treated as if  they  map  to  an
              empty  list,  and it is legal for there to be no items to append to the list. It is
              an error for the value that the key maps to to not be representable as a list.

       dict merge ?dictionaryValue ...?
              Return a dictionary that contains the  contents  of  each  of  the  dictionaryValue
              arguments.   Where  two  (or more) dictionaries contain a mapping for the same key,
              the resulting dictionary  maps  that  key  to  the  value  according  to  the  last
              dictionary on the command line containing a mapping for that key.

       dict remove dictionaryValue ?key ...?
              Return  a  new  dictionary that is a copy of an old one passed in as first argument
              except without mappings for each of the keys listed.  It is legal for there  to  be
              no  keys  to  remove, and it also legal for any of the keys to be removed to not be
              present in the input dictionary in the first place.

       dict replace dictionaryValue ?key value ...?
              Return a new dictionary that is a copy of an old one passed in  as  first  argument
              except  with some values different or some extra key/value pairs added. It is legal
              for this command to be called with no key/value pairs, but illegal for this command
              to be called with a key but no value.

       dict set dictionaryVariable key ?key ...? value
              This  operation  takes  the  name  of  a variable containing a dictionary value and
              places an updated dictionary value in that variable containing a mapping  from  the
              given  key  to  the  given  value.  When  multiple keys are present, this operation
              creates or updates a chain of nested dictionaries.

       dict size dictionaryValue
              Return the number of key/value mappings in the given dictionary value.

       dict unset dictionaryVariable key ?key ...?
              This operation (the companion to dict set) takes the name of a variable  containing
              a  dictionary  value  and  places an updated dictionary value in that variable that
              does not contain a mapping for the given key. Where multiple keys are present, this
              describes a path through nested dictionaries to the mapping to remove. At least one
              key must be specified, but the last key on the key-path need not exist.  All  other
              components on the path must exist.

       dict update dictionaryVariable key varName ?key varName ...? body
              Execute the Tcl script in body with the value for each key (as found by reading the
              dictionary value in dictionaryVariable) mapped to the variable varName.  There  may
              be  multiple  key/varName pairs. If a key does not have a mapping, that corresponds
              to an unset varName. When body terminates, any changes  made  to  the  varNames  is
              reflected    back    to    the   dictionary   within   dictionaryVariable   (unless
              dictionaryVariable  itself  becomes  unreadable,  when  all  updates  are  silently
              discarded),  even  if  the  result  of  body  is  an  error  or  some other kind of
              exceptional exit. The result of dict update is (unless some kind of  error  occurs)
              the result of the evaluation of body.

              Each  varName  is  mapped in the scope enclosing the dict update; it is recommended
              that this command only be used in a local  scope  (procedure  or  lambda  term  for
              apply).  Because  of  this, the variables set by dict update will continue to exist
              after the command finishes (unless explicitly unset).  Note  that  the  mapping  of
              values  to  variables  does  not  use  traces;  changes to the dictionaryVariable's
              contents only happen when body terminates.

       dict values dictionaryValue ?globPattern?
              Return a list of all values  in  the  given  dictionary  value.  If  a  pattern  is
              supplied,  only those values that match it (according to the rules of string match)
              will be returned. The returned values will  be  in  the  order  of  that  the  keys
              associated with those values were inserted into the dictionary.

       dict with dictionaryVariable ?key ...? body
              Execute  the  Tcl  script in body with the value for each key in dictionaryVariable
              mapped (in a manner similarly to dict update) to a variable  with  the  same  name.
              Where   one  or  more  keys  are  available,  these  indicate  a  chain  of  nested
              dictionaries, with the innermost dictionary  being  the  one  opened  out  for  the
              execution  of  body. As with dict update, making dictionaryVariable unreadable will
              make the updates to the dictionary be discarded,  and  this  also  happens  if  the
              contents  of  dictionaryVariable  are adjusted so that the chain of dictionaries no
              longer exists. The result of dict with is (unless some kind of  error  occurs)  the
              result of the evaluation of body.

              The  variables  are  mapped in the scope enclosing the dict with; it is recommended
              that this command only be used in a local  scope  (procedure  or  lambda  term  for
              apply).  Because  of  this,  the  variables set by dict with will continue to exist
              after the command finishes (unless explicitly unset).  Note  that  the  mapping  of
              values  to  variables  does  not  use  traces;  changes to the dictionaryVariable's
              contents only happen when body terminates.

              If the dictionaryVariable contains a value that is not a dictionary  at  the  point
              when the body terminates (which can easily happen if the name is the same as any of
              the keys in dictionary) then an error occurs at that point. This  command  is  thus
              not  recommended for use when the keys in the dictionary are expected to clash with
              the dictionaryVariable  name  itself.  Where  the  contained  key  does  map  to  a
              dictionary,  the  net  effect  is  to  combine that inner dictionary into the outer
              dictionary; see the EXAMPLES below for an illustration of this.

DICTIONARY VALUES

       Dictionaries are values that contain an efficient, order-preserving mapping from arbitrary
       keys to arbitrary values.  Each key in the dictionary maps to a single value.  They have a
       textual format that is exactly that of any list with an even number of elements, with each
       mapping in the dictionary being represented as two items in the list. When a command takes
       a dictionary and produces a new dictionary based on it (either returning it or writing  it
       back into the variable that the starting dictionary was read from) the new dictionary will
       have the same order of keys, modulo any deleted keys and with new keys  added  on  to  the
       end.   When  a string is interpreted as a dictionary and it would otherwise have duplicate
       keys, only the last value for a particular key is used; the others  are  ignored,  meaning
       that,  “apple  banana”  and  “apple carrot apple banana” are equivalent dictionaries (with
       different string representations).

       Operations that derive a new dictionary from an old one (e.g., updates like dict  set  and
       dict  unset)  preserve the order of keys in the dictionary. The exceptions to this are for
       any new keys they add, which are appended to the sequence, and any keys that are  removed,
       which are excised from the order.

EXAMPLES

       Basic dictionary usage:

              # Make a dictionary to map extensions to descriptions
              set filetypes [dict create .txt "Text File" .tcl "Tcl File"]

              # Add/update the dictionary
              dict set filetypes .tcl "Tcl Script"
              dict set filetypes .tm  "Tcl Module"
              dict set filetypes .gif "GIF Image"
              dict set filetypes .png "PNG Image"

              # Simple read from the dictionary
              set ext ".tcl"
              set desc [dict get $filetypes $ext]
              puts "$ext is for a $desc"

              # Somewhat more complex, with existence test
              foreach filename [glob *] {
                  set ext [file extension $filename]
                  if {[dict exists $filetypes $ext]} {
                      puts "$filename is a [dict get $filetypes $ext]"
                  }
              }

       Constructing and using nested dictionaries:

              # Data for one employee
              dict set employeeInfo 12345-A forenames "Joe"
              dict set employeeInfo 12345-A surname   "Schmoe"
              dict set employeeInfo 12345-A street "147 Short Street"
              dict set employeeInfo 12345-A city   "Springfield"
              dict set employeeInfo 12345-A phone  "555-1234"
              # Data for another employee
              dict set employeeInfo 98372-J forenames "Anne"
              dict set employeeInfo 98372-J surname   "Other"
              dict set employeeInfo 98372-J street "32995 Oakdale Way"
              dict set employeeInfo 98372-J city   "Springfield"
              dict set employeeInfo 98372-J phone  "555-8765"
              # The above data probably ought to come from a database...

              # Print out some employee info
              set i 0
              puts "There are [dict size $employeeInfo] employees"
              dict for {id info} $employeeInfo {
                 puts "Employee #[incr i]: $id"
                 dict with info {
                    puts "   Name: $forenames $surname"
                    puts "   Address: $street, $city"
                    puts "   Telephone: $phone"
                 }
              }
              # Another way to iterate and pick out names...
              foreach id [dict keys $employeeInfo] {
                 puts "Hello, [dict get $employeeInfo $id forenames]!"
              }

       A localizable version of string toupper:

              # Set up the basic C locale
              set capital [dict create C [dict create]]
              foreach c [split {abcdefghijklmnopqrstuvwxyz} ""] {
                 dict set capital C $c [string toupper $c]
              }

              # English locales can luckily share the "C" locale
              dict set capital en [dict get $capital C]
              dict set capital en_US [dict get $capital C]
              dict set capital en_GB [dict get $capital C]

              # ... and so on for other supported languages ...

              # Now get the mapping for the current locale and use it.
              set upperCaseMap [dict get $capital $env(LANG)]
              set upperCase [string map $upperCaseMap $string]

       Showing the detail of dict with:

              proc sumDictionary {varName} {
                 upvar 1 $varName vbl
                 foreach key [dict keys $vbl] {
                    # Manufacture an entry in the subdictionary
                    dict set vbl $key total 0
                    # Add the values and remove the old
                    dict with vbl $key {
                       set total [expr {$x + $y + $z}]
                       unset x y z
                    }
                 }
                 puts "last total was $total, for key $key"
              }

              set myDict {
                 a {x 1 y 2 z 3}
                 b {x 6 y 5 z 4}
              }

              sumDictionary myDict
              #    prints: last total was 15, for key b

              puts "dictionary is now \"$myDict\""
              #    prints: dictionary is now "a {total 6} b {total 15}"

       When dict with is used with a key that clashes with the name of the dictionary variable:

              set foo {foo {a b} bar 2 baz 3}
              dict with foo {}
              puts $foo
              #    prints: a b foo {a b} bar 2 baz 3

SEE ALSO

       append(3tcl), array(3tcl), foreach(3tcl), incr(3tcl), list(3tcl), lappend(3tcl), set(3tcl)

KEYWORDS

       dictionary, create, update, lookup, iterate, filter