dict(n) - phpMan

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dict(n)                               Tcl Built-In Commands                               dict(n)



_________________________________________________________________________________________________

NAME
       dict - Manipulate dictionaries

SYNOPSIS
       dict option arg ?arg ...?
_________________________________________________________________

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 dic-
              tionary  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 associ-
              ated 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 exam-
              ple, 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 speci-
              fied) 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 dictio-
              nary though the format of this data is dependent on the implementation of the  dic-
              tionary.  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 argu-
              ments.  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  cre-
              ates 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  dictionaryVari-
              able  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  con-
              tents only happen when body terminates.

       dict values dictionaryValue ?globPattern?
              Return  a  list  of  all values in the given dictionary value. If a pattern is sup-
              plied, 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 associ-
              ated 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  dictionar-
              ies,  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  con-
              tents 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 dictio-
              nary, 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(n), array(n), foreach(n), incr(n), list(n), lappend(n), set(n)

KEYWORDS
       dictionary, create, update, lookup, iterate, filter



Tcl                                            8.5                                        dict(n)

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