1dict(n) Tcl Built-In Commands dict(n)
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8 dict - Manipulate dictionaries
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11 dict option arg ?arg ...?
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15 Performs one of several operations on dictionary values or variables
16 containing dictionary values (see the DICTIONARY VALUES section below
17 for a description), depending on option. The legal options (which may
18 be abbreviated) are:
19 dict append dictionaryVariable key ?string ...?
21 This appends the given string (or strings) to the value that the
22 given key maps to in the dictionary value contained in the given
23 variable, writing the resulting dictionary value back to that
24 variable. Non-existent keys are treated as if they map to an
25 empty string.
26 dict create ?key value ...?
28 Create a new dictionary that contains each of the key/value map‐
29 pings listed as arguments (keys and values alternating, with
30 each key being followed by its associated value.)
31 dict exists dictionaryValue key ?key ...?
33 This returns a boolean value indicating whether the given key
34 (or path of keys through a set of nested dictionaries) exists in
35 the given dictionary value. This returns a true value exactly
36 when dict get on that path will succeed.
37 dict filter dictionaryValue filterType arg ?arg ...?
39 This takes a dictionary value and returns a new dictionary that
40 contains just those key/value pairs that match the specified
41 filter type (which may be abbreviated.) Supported filter types
42 are:
43 dict filter dictionaryValue key globPattern
45 The key rule only matches those key/value pairs whose
46 keys match the given pattern (in the style of string
47 match.)
48 dict filter dictionaryValue script {keyVar valueVar} script
50 The script rule tests for matching by assigning the key
51 to the keyVar and the value to the valueVar, and then
52 evaluating the given script which should return a boolean
53 value (with the key/value pair only being included in the
54 result of the dict filter when a true value is returned.)
55 Note that the first argument after the rule selection
56 word is a two-element list. If the script returns with a
57 condition of TCL_BREAK, no further key/value pairs are
58 considered for inclusion in the resulting dictionary, and
59 a condition of TCL_CONTINUE is equivalent to a false
60 result. The key/value pairs are tested in the order in
61 which the keys were inserted into the dictionary.
62 dict filter dictionaryValue value globPattern
64 The value rule only matches those key/value pairs whose
65 values match the given pattern (in the style of string
66 match.)
67 dict for {keyVar valueVar} dictionaryValue body
69 This command takes three arguments, the first a two-element list
70 of variable names (for the key and value respectively of each
71 mapping in the dictionary), the second the dictionary value to
72 iterate across, and the third a script to be evaluated for each
73 mapping with the key and value variables set appropriately (in
74 the manner of foreach.) The result of the command is an empty
75 string. If any evaluation of the body generates a TCL_BREAK
76 result, no further pairs from the dictionary will be iterated
77 over and the dict for command will terminate successfully imme‐
78 diately. If any evaluation of the body generates a TCL_CONTINUE
79 result, this shall be treated exactly like a normal TCL_OK
80 result. The order of iteration is the order in which the keys
81 were inserted into the dictionary.
82 dict get dictionaryValue ?key ...?
84 Given a dictionary value (first argument) and a key (second
85 argument), this will retrieve the value for that key. Where sev‐
86 eral keys are supplied, the behaviour of the command shall be as
87 if the result of dict get $dictVal $key was passed as the first
88 argument to dict get with the remaining arguments as second (and
89 possibly subsequent) arguments. This facilitates lookups in
90 nested dictionaries. For example, the following two commands are
91 equivalent:
92 dict get $dict foo bar spong
93 dict get [dict get [dict get $dict foo] bar] spong
94 If no keys are provided, dict would return a list containing
95 pairs of elements in a manner similar to array get. That is, the
96 first element of each pair would be the key and the second ele‐
97 ment would be the value for that key.
98 It is an error to attempt to retrieve a value for a key that is
100 not present in the dictionary.
101 dict incr dictionaryVariable key ?increment?
103 This adds the given increment value (an integer that defaults to
104 1 if not specified) to the value that the given key maps to in
105 the dictionary value contained in the given variable, writing
106 the resulting dictionary value back to that variable. Non-exis‐
107 tent keys are treated as if they map to 0. It is an error to
108 increment a value for an existing key if that value is not an
109 integer.
110 dict info dictionaryValue
112 This returns information (intended for display to people) about
113 the given dictionary though the format of this data is dependent
114 on the implementation of the dictionary. For dictionaries that
115 are implemented by hash tables, it is expected that this will
116 return the string produced by Tcl_HashStats, similar to array
117 info.
118 dict keys dictionaryValue ?globPattern?
120 Return a list of all keys in the given dictionary value. If a
121 pattern is supplied, only those keys that match it (according to
122 the rules of string match) will be returned. The returned keys
123 will be in the order that they were inserted into the dictio‐
124 nary.
125 dict lappend dictionaryVariable key ?value ...?
127 This appends the given items to the list value that the given
128 key maps to in the dictionary value contained in the given vari‐
129 able, writing the resulting dictionary value back to that vari‐
130 able. Non-existent keys are treated as if they map to an empty
131 list, and it is legal for there to be no items to append to the
132 list. It is an error for the value that the key maps to to not
133 be representable as a list.
134 dict merge ?dictionaryValue ...?
136 Return a dictionary that contains the contents of each of the
137 dictionaryValue arguments. Where two (or more) dictionaries
138 contain a mapping for the same key, the resulting dictionary
139 maps that key to the value according to the last dictionary on
140 the command line containing a mapping for that key.
141 dict remove dictionaryValue ?key ...?
143 Return a new dictionary that is a copy of an old one passed in
144 as first argument except without mappings for each of the keys
145 listed. It is legal for there to be no keys to remove, and it
146 also legal for any of the keys to be removed to not be present
147 in the input dictionary in the first place.
148 dict replace dictionaryValue ?key value ...?
150 Return a new dictionary that is a copy of an old one passed in
151 as first argument except with some values different or some
152 extra key/value pairs added. It is legal for this command to be
153 called with no key/value pairs, but illegal for this command to
154 be called with a key but no value.
155 dict set dictionaryVariable key ?key ...? value
157 This operation takes the name of a variable containing a dictio‐
158 nary value and places an updated dictionary value in that vari‐
159 able containing a mapping from the given key to the given value.
160 When multiple keys are present, this operation creates or
161 updates a chain of nested dictionaries.
162 dict size dictionaryValue
164 Return the number of key/value mappings in the given dictionary
165 value.
166 dict unset dictionaryVariable key ?key ...?
168 This operation (the companion to dict set) takes the name of a
169 variable containing a dictionary value and places an updated
170 dictionary value in that variable that does not contain a map‐
171 ping for the given key. Where multiple keys are present, this
172 describes a path through nested dictionaries to the mapping to
173 remove. At least one key must be specified, but the last key on
174 the key-path need not exist. All other components on the path
175 must exist.
176 dict update dictionaryVariable key varName ?key varName ...? body
178 Execute the Tcl script in body with the value for each key (as
179 found by reading the dictionary value in dictionaryVariable)
180 mapped to the variable varName. There may be multiple key/var‐
181 Name pairs. If a key does not have a mapping, that corresponds
182 to an unset varName. When body terminates, any changes made to
183 the varNames is reflected back to the dictionary within dictio‐
184 naryVariable (unless dictionaryVariable itself becomes unread‐
185 able, when all updates are silently discarded), even if the
186 result of body is an error or some other kind of exceptional
187 exit. The result of dict update is (unless some kind of error
188 occurs) the result of the evaluation of body. Note that the map‐
189 ping of values to variables does not use traces; changes to the
190 dictionaryVariable's contents only happen when body terminates.
191 dict values dictionaryValue ?globPattern?
193 Return a list of all values in the given dictionary value. If a
194 pattern is supplied, only those values that match it (according
195 to the rules of string match) will be returned. The returned
196 values will be in the order of that the keys associated with
197 those values were inserted into the dictionary.
198 dict with dictionaryVariable ?key ...? body
200 Execute the Tcl script in body with the value for each key in
201 dictionaryVariable mapped (in a manner similarly to dict update)
202 to a variable with the same name. Where one or more keys are
203 available, these indicate a chain of nested dictionaries, with
204 the innermost dictionary being the one opened out for the execu‐
205 tion of body. As with dict update, making dictionaryVariable
206 unreadable will make the updates to the dictionary be discarded,
207 and this also happens if the contents of dictionaryVariable are
208 adjusted so that the chain of dictionaries no longer exists. The
209 result of dict with is (unless some kind of error occurs) the
210 result of the evaluation of body. Note that the mapping of val‐
211 ues to variables does not use traces; changes to the dictionary‐
212 Variable's contents only happen when body terminates.
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215 Dictionaries are values that contain an efficient, order-preserving
216 mapping from arbitrary keys to arbitrary values. Each key in the dic‐
217 tionary maps to a single value. They have a textual format that is
218 exactly that of any list with an even number of elements, with each
219 mapping in the dictionary being represented as two items in the list.
220 When a command takes a dictionary and produces a new dictionary based
221 on it (either returning it or writing it back into the variable that
222 the starting dictionary was read from) the new dictionary will have the
223 same order of keys, modulo any deleted keys and with new keys added on
224 to the end. When a string is interpreted as a dictionary and it would
225 otherwise have duplicate keys, only the last value for a particular key
226 is used; the others are ignored, meaning that, “apple banana” and
227 “apple carrot apple banana” are equivalent dictionaries (with different
228 string representations).
229
231 Constructing and using nested dictionaries:
232 # Data for one employee
233 dict set employeeInfo 12345-A forenames "Joe"
234 dict set employeeInfo 12345-A surname "Schmoe"
235 dict set employeeInfo 12345-A street "147 Short Street"
236 dict set employeeInfo 12345-A city "Springfield"
237 dict set employeeInfo 12345-A phone "555-1234"
238 # Data for another employee
239 dict set employeeInfo 98372-J forenames "Anne"
240 dict set employeeInfo 98372-J surname "Other"
241 dict set employeeInfo 98372-J street "32995 Oakdale Way"
242 dict set employeeInfo 98372-J city "Springfield"
243 dict set employeeInfo 98372-J phone "555-8765"
244 # The above data probably ought to come from a database...
245 # Print out some employee info
247 set i 0
248 puts "There are [dict size $employeeInfo] employees"
249 dict for {id info} $employeeInfo {
250 puts "Employee #[incr i]: $id"
251 dict with info {
252 puts " Name: $forenames $surname"
253 puts " Address: $street, $city"
254 puts " Telephone: $phone"
255 }
256 }
257 # Another way to iterate and pick out names...
258 foreach id [dict keys $employeeInfo] {
259 puts "Hello, [dict get $employeeInfo $id forenames]!"
260 }
261 A localizable version of string toupper:
263 # Set up the basic C locale
264 set capital [dict create C [dict create]]
265 foreach c [split {abcdefghijklmnopqrstuvwxyz} ""] {
266 dict set capital C $c [string toupper $c]
267 }
268 # English locales can luckily share the "C" locale
270 dict set capital en [dict get $capital C]
271 dict set capital en_US [dict get $capital C]
272 dict set capital en_GB [dict get $capital C]
273 # ... and so on for other supported languages ...
275 # Now get the mapping for the current locale and use it.
277 set upperCaseMap [dict get $capital $env(LANG)]
278 set upperCase [string map $upperCaseMap $string]
279
281 append(n), array(n), foreach(n), incr(n), list(n), lappend(n), set(n)
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284 dictionary, create, update, lookup, iterate, filter
285Tcl 8.5 dict(n)