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{{draft task}}
 
Create a Hash/Associative Array/Dictionary-like object, that can be initialized with some default key/value pairs using the languages native method of object creation. The object should behave like a native Hash/Associative Array/Dictionary of the language, if any, but with the following differences:
 
* No new itemkeys can be added;
* Keys cannot be removed;
* Item cannot be deleted, (but native delete method may used to reset the item's value to default) ;
* Attempting to delete a key should set that keys value back to that used during initialisation.
(The value assigned to keys may be changed by normal assignment however).
 
ItIf the language supports '''Magic Methods''', then show how these work.
 
=={{header|BASIC}}==
==={{header|BASIC256}}===
<syntaxhighlight lang="basic256">map mapa
mapa["A"] = 65
mapa["B"] = 66
mapa["C"] = 67
 
foreach valor in mapa
print valor
print mapa[valor]
next valor</syntaxhighlight>
{{out}}
<pre>A
65
B
66
C
67</pre>
 
==={{header|FreeBASIC}}===
FB doesn't have Dict natively, but we can implement them via Type
<syntaxhighlight lang="freebasic">Type dict
m1 As String*1
m2 As Integer
End Type
 
Dim mapOf(1 To 3) As dict => {("A", 65), ("B", 66), ("C", 67)}
 
For i As Integer = 1 To Ubound(mapOf)
Print mapOf(i).m1
Print mapOf(i).m2
Next i</syntaxhighlight>
{{out}}
<pre>A
65
B
66
C
67</pre>
 
=={{header|C++}}==
<syntaxhighlight lang="cpp">#include <iostream>
#include <map>
#include <utility>
 
using namespace std;
 
template<typename T>
class FixedMap : private T
{
// Two standard maps are used to implement FixedMap. One as a private
// base class which will allow the values (but not the keys) to be modified.
// Members of a private base class are not exposed to the derived class which will
// prevent keys from being added or deleted. Another map will hold copies of
// the initial values.
T m_defaultValues;
public:
FixedMap(T map)
: T(map), m_defaultValues(move(map)){}
// Expose members of the base class that do not modify the map.
using T::cbegin;
using T::cend;
using T::empty;
using T::find;
using T::size;
 
// Also expose members that can modify values but not add or remove keys.
using T::at;
using T::begin;
using T::end;
// The [] operator will normally add a new key if the key is not already in the
// map. Instead, throw an error if the key is missing.
auto& operator[](typename T::key_type&& key)
{
// Make it behave like at()
return this->at(forward<typename T::key_type>(key));
}
// Instead of removing a key, change the sematics of erase() to restore
// the original value of the key.
void erase(typename T::key_type&& key)
{
T::operator[](key) = m_defaultValues.at(key);
}
 
// Also change the sematics of clear() to restore all keys
void clear()
{
// Reset the base class using the defaults
T::operator=(m_defaultValues);
}
};
 
// Print the contents of a map
auto PrintMap = [](const auto &map)
{
for(auto &[key, value] : map)
{
cout << "{" << key << " : " << value << "} ";
}
cout << "\n\n";
};
 
int main(void)
{
// Create a fixed map based on the standard map
cout << "Map intialized with values\n";
FixedMap<map<string, int>> fixedMap ({
{"a", 1},
{"b", 2}});
PrintMap(fixedMap);
cout << "Change the values of the keys\n";
fixedMap["a"] = 55;
fixedMap["b"] = 56;
PrintMap(fixedMap);
cout << "Reset the 'a' key\n";
fixedMap.erase("a");
PrintMap(fixedMap);
cout << "Change the values the again\n";
fixedMap["a"] = 88;
fixedMap["b"] = 99;
PrintMap(fixedMap);
cout << "Reset all keys\n";
fixedMap.clear();
PrintMap(fixedMap);
try
{
// Adding or retrieving a missing key is a run time error
cout << "Try to add a new key\n";
fixedMap["newKey"] = 99;
}
catch (exception &ex)
{
cout << "error: " << ex.what();
}
}
</syntaxhighlight>
{{out}}
<pre>Map intialized with values
{a : 1} {b : 2}
 
Change the values of the keys
{a : 55} {b : 56}
 
Reset the 'a' key
{a : 1} {b : 56}
 
Change the values the again
{a : 88} {b : 99}
 
Reset all keys
{a : 1} {b : 2}
 
Try to add a new key
error: map::at</pre>
 
=={{header|D}}==
{{trans|Python}}
<syntaxhighlight lang="d">struct DefaultAA(TK, TV) {
TV[TK] standard, current;
 
this(TV[TK] default_) pure /*nothrow*/ @safe {
this.standard = default_;
this.current = default_.dup;
}
 
alias current this;
 
void remove(in TK key) pure nothrow {
current[key] = standard[key];
}
 
void clear() pure /*nothrow*/ @safe {
current = standard.dup;
}
}
 
void main() {
import std.stdio;
auto d = ["a": 1, "b": 2].DefaultAA!(string, int);
 
d.writeln; // ["a":1, "b":2]
d["a"] = 55; d["b"] = 66;
d.writeln; // ["a":55, "b":66]
d.clear;
d.writeln; // ["a":1, "b":2]
d["a"] = 55; d["b"] = 66;
d["a"].writeln; // 55
d.remove("a");
d.writeln; // ["a":1, "b":66]
}</syntaxhighlight>
{{out}}
<pre>["a":1, "b":2]
["a":55, "b":66]
["a":1, "b":2]
55
["a":1, "b":66]</pre>
 
=={{header|Go}}==
Go's built-in map type is mutable and so, to complete this task, we need to create a read-only wrapper for it which doesn't permit further items to be added or existing items to be deleted though does allow them to be reset to their default value.
 
First create a sub-directory, romap, of the project directory and place the following package in it:
<syntaxhighlight lang="go">package romap
 
type Romap struct{ imap map[byte]int }
 
// Create new read-only wrapper for the given map.
func New(m map[byte]int) *Romap {
if m == nil {
return nil
}
return &Romap{m}
}
 
// Retrieve value for a given key, if it exists.
func (rom *Romap) Get(key byte) (int, bool) {
i, ok := rom.imap[key]
return i, ok
}
 
// Reset value for a given key, if it exists.
func (rom *Romap) Reset(key byte) {
_, ok := rom.imap[key]
if ok {
rom.imap[key] = 0 // default value of int
}
}</syntaxhighlight>
 
This package can now be imported and used within the main package as follows:
<syntaxhighlight lang="go">package main
 
import (
"./romap"
"fmt"
)
 
func main() {
// create a normal map
m := map[byte]int{'A': 65, 'B': 66, 'C': 67}
 
// place it in a read-only wrapper so no new item can be added or item deleted.
rom := romap.New(m)
 
// retrieve value represented by 'C' say
i, _ := rom.Get('C')
fmt.Println("'C' maps to", i)
 
// reset this to default value (doesn't actually delete the key)
rom.Reset('C')
i, _ = rom.Get('C')
fmt.Println("'C' now maps to", i)
}</syntaxhighlight>
 
{{out}}
<pre>
'C' maps to 67
'C' now maps to 0
</pre>
 
=={{header|J}}==
Line 12 ⟶ 282:
Given a list of keys and an associated list of values, the idiomatic way of expressing this concept in J would be:
 
<langsyntaxhighlight lang="j">lookup=: values {~ keys&i.</langsyntaxhighlight>
 
For example:
 
<langsyntaxhighlight lang="j"> lookup=: 10 20 30 40 50 {~ (;:'this is a test')&i.
lookup ;:'a test'
30 40</langsyntaxhighlight>
 
Notes:
Line 27 ⟶ 297:
 
3) In J, objects are always referenced, but all data is passed by value. This means that objects can never be passed to a function -- only a reference to an object (its name) can be passed. This means that objects exist only in the way things are named, in J. So for the most part, we do not call things "objects" in J, and this task has nothing to do with what are called "objects" in J. However, this does demonstrate how things are created in J -- you write their definition, and can use them and/or assign to names or inspect them or whatever else.
 
=={{header|Java}}==
 
Java supports unmodifiable maps, sets, lists, and other more specialized unmodifiable collections. In this example, we have a unmodifiable map. We first create an ordinary map, modify as needed, then call the <code>Collections.unmodifiableMap</code>. We can subsequently read the map, but modification is not permitted. The returned map will subsequently throw a <code>UnsupportedOperationException</code> exception if a mutation operator is called. Several are demonstrated below.
 
<syntaxhighlight lang="java">
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
 
// Title: Create an object/Native demonstration
 
public class ImmutableMap {
 
public static void main(String[] args) {
Map<String,Integer> hashMap = getImmutableMap();
try {
hashMap.put("Test", 23);
}
catch (UnsupportedOperationException e) {
System.out.println("ERROR: Unable to put new value.");
}
try {
hashMap.clear();
}
catch (UnsupportedOperationException e) {
System.out.println("ERROR: Unable to clear map.");
}
try {
hashMap.putIfAbsent("Test", 23);
}
catch (UnsupportedOperationException e) {
System.out.println("ERROR: Unable to put if absent.");
}
for ( String key : hashMap.keySet() ) {
System.out.printf("key = %s, value = %s%n", key, hashMap.get(key));
}
}
private static Map<String,Integer> getImmutableMap() {
Map<String,Integer> hashMap = new HashMap<>();
hashMap.put("Key 1", 34);
hashMap.put("Key 2", 105);
hashMap.put("Key 3", 144);
 
return Collections.unmodifiableMap(hashMap);
}
}
</syntaxhighlight>
 
{out}}
<pre>
ERROR: Unable to put new value.
ERROR: Unable to clear map.
ERROR: Unable to put if absent.
key = Key 1, value = 34
key = Key 2, value = 105
key = Key 3, value = 144
</pre>
 
=={{header|JavaScript}}==
Line 33 ⟶ 364:
{{works with|JavaScript|1.7}}
 
<langsyntaxhighlight lang="javascript">var keyError = new Error("Invalid Key Error (FixedKeyDict)") ;
 
function FixedKeyDict(obj)
Line 95 ⟶ 426:
return "FixedKeyDict{" + s + "}" ;
} ;
}</langsyntaxhighlight>
 
Test run:
 
<langsyntaxhighlight lang="javascript">
const BR = "<BR>\n"
 
Line 133 ⟶ 464:
pl("error test : " + e.message) ;
}
</syntaxhighlight>
</lang>
 
output :
Line 154 ⟶ 485:
error test : Invalid Key Error (FixedKeyDict)
</pre>
 
=={{header|jq}}==
jq objects are JSON objects and can be created using JSON syntax, e.g. <syntaxhighlight lang="jq">{"language": "jq"}</syntaxhighlight>
Objects can also be created programmatically, e.g. <syntaxhighlight lang="jq">{"one": 1} + {"two": 2}</syntaxhighlight>
 
jq objects, however, are really just values: they are immutable, and cannot be "deleted" any more than the number 1 can be deleted.
 
=={{header|Julia}}==
<syntaxhighlight lang="julia">
using BackedUpImmutable
 
function testBackedUpImmutableDict()
fibr = BackedUpImmutableDict{String,Int64}(["a" => 0, "b" => 1, "c" => 1, "d" => 2,
"e" => 3, "f" => 5, "g" => 8, "h" => 13, "i" => 21, "j" => 34, "extra" => -1])
 
x = fibr["extra"]
@test x == -1
fibr["extra"] = 0
y = fibr["extra"]
@test y == 0
restore!(fibr, "extra")
z = fibr["extra"]
@test z == -1
@test_throws String begin fibr["k"] = 55 end
fibr["a"] = 9
fibr["b"] = 7
# test restore all to default
restoreall!(fibr)
@test fibr["a"] == 0
end
</syntaxhighlight>
All tests pass.
 
=={{header|Kotlin}}==
<syntaxhighlight lang="scala">// version 1.1.2
 
fun main(args: Array<String>) {
// This line creates a read-only map which cannot be changed in any way nor cleared
val map = mapOf('A' to 65, 'B' to 66, 'C' to 67)
println(map)
}</syntaxhighlight>
 
{{out}}
<pre>
{A=65, B=66, C=67}
</pre>
 
=={{header|M2000 Interpreter}}==
{{trans|C sharp}}
<syntaxhighlight lang="m2000 interpreter">
Module CheckIt {
Class LockedHash {
Private:
inventory Vars ' no same keys
unlock
module nosuchvariable {
Error "No such value:"+letter$
}
module NoNewItem {
Error "No new item, use unlock method before"
}
module NoRemoveItem {
Error "Can't remove item, use unlock method before"
}
Public:
module Unlock {
.unlock<=True
}
module Writeln {
m=each(.Vars)
while m {
Print Quote$(Eval$(m, m^));",";Eval(m),
}
Print
}
Value (st$){
st$=Ucase$(st$)
if exist(.Vars, st$) then =Eval(.Vars) : Exit
.nosuchvariable st$
}
Set (st$){
st$=Ucase$(st$)
Read val
if exist(.Vars, st$) then Return .Vars, st$:=val : Exit
If .unlock then { Append .Vars, st$:=val} Else .NoNewItem
}
module Remove (st$) {
if not .unlock then .NoRemoveItem
st$=Ucase$(st$)
Try {
delete .Vars, st$
}
}
module Clear {
Clear .Vars
}
Class: ' this part exist only at construction
module LockedHash {
While match("SN") {
read st$, val
st$=ucase$(st$)
\\ if we append key which exist we get error
Append .Vars, st$:=val
}
}
}
d=LockedHash("a", 1, "b", 2)
d.writeln
d("a")=55 : d("b")=66
d.writeln
d.clear
d.writeln
d.unlock
d("a")=55 : d("b")=66
Print d("a")=55, d("a")/d("b")<1
d.remove "a"
d.writeln
}
Checkit
</syntaxhighlight>
 
=={{header|Mathematica}} / {{header|Wolfram Language}}==
<syntaxhighlight lang="mathematica">a[1] = "Do not modify after creation";
a[2] = "Native demonstration";
Protect[a];</syntaxhighlight>
Example usage:
<pre>a[3] = 2
->Set::write: Tag a in a[1] is Protected. >>
</pre>
 
=={{header|Nim}}==
We leverage native stdlib table as our own object by implementing limited actual native table functionalities.
<syntaxhighlight lang="nim">import tables, options
 
type
MyTable = object
table: TableRef[string, int]
 
# return empty if the key is not available
proc `[]`(m: MyTable, key: string): Option[int] =
if key in m.table: result = some m.table[key]
else: result = none int
 
# update an item, doing nothing if the key is available during first initialization
proc `[]=`(m: var MyTable, key: string, val: int) =
if key notin m.table: return
m.table[key] = val
 
proc reset(m: var MyTable) =
for _, v in m.table.mpairs: v = 0
 
# sugar for defining MyTable object
proc toTable(vals: openarray[(string, int)]): MyTable =
result.table = newTable vals
 
proc main =
# MyTable construction
var myobj = {"key1": 1, "key2": 2, "key3": 3}.toTable
# test getting existing key
let val1 = myobj["key1"]
if val1.isSome: echo "val1: ", val1.get
 
# test adding new key
myobj["key4"] = 4
let val4 = myobj["key4"]
if val4.isSome: echo val4.get
else: echo "val4 is empty"
 
# test reset and test whether its value is zero-ed
reset myobj
doAssert myobj["key3"].get == 0
 
main()
</syntaxhighlight>
{{output}}
<pre>
val1: 1
val4 is empty</pre>
 
=={{header|Perl}}==
<syntaxhighlight lang="perl">use strict;
 
package LockedHash;
use parent 'Tie::Hash';
use Carp;
 
sub TIEHASH {
my $cls = shift;
my %h = @_;
bless \%h, ref $cls || $cls;
}
 
sub STORE {
my ($self, $k, $v) = @_;
croak "Can't add key $k" unless exists $self->{$k};
$self->{$k} = $v;
}
 
sub FETCH {
my ($self, $k) = @_;
croak "No key $k" unless exists $self->{$k};
$self->{$k};
}
 
sub DELETE {
my ($self, $k) = @_;
croak "No key $k" unless exists $self->{$k};
$self->{$k} = 0;
}
 
sub CLEAR { } # ignored
sub EXISTS { exists shift->{+shift} }
 
sub FIRSTKEY {
my $self = shift;
keys %$self;
each %$self;
}
 
sub NEXTKEY {
my $self = shift;
each %$self;
}
 
sub lock_hash :prototype(\%) {
my $ref = shift;
tie(%$ref, __PACKAGE__, %$ref);
}
 
1;
 
my %h = (a => 3, b => 4, c => 5);
 
# lock down %h
LockedHash::lock_hash(%h);
 
# show hash content and iteration
for (sort keys %h) { print "$_ => $h{$_}\n"; }
 
# try delete b
delete $h{b};
print "\nafter deleting b: b => $h{b}\n";
 
# change value of a
$h{a} = 100;
print "\na => $h{a}\n";
 
# add a new key x: will die
eval { $h{x} = 1 };
if ($@) { print "Operation error: $@" }</syntaxhighlight>output:<syntaxhighlight lang="text">a => 3
b => 4
c => 5
 
after deleting b: b => 0
 
a => 100
operation error: Can't add key x at test.pl line 14
LockedHash::STORE('LockedHash=HASH(0x8cebe14)', 'x', 1) called at test.pl line 66
eval {...} called at test.pl line 66</syntaxhighlight>
 
=={{header|Phix}}==
There is no native "read-only" setting on phix dictionaries, so the following wraps a pair of them to
provide the requested functionality.
<!--<syntaxhighlight lang="phix">(phixonline)-->
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
<span style="color: #008080;">enum</span> <span style="color: #000000;">STD</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">CUR</span>
<span style="color: #004080;">sequence</span> <span style="color: #000000;">fkds</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{}</span> <span style="color: #000080;font-style:italic;">-- fixed key dictionaries ;-)</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">freelist</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">fkd_destroy</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">id</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">std</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">]</span>
<span style="color: #7060A8;">destroy_dict</span><span style="color: #0000FF;">(</span><span style="color: #000000;">std</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">destroy_dict</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">freelist</span>
<span style="color: #000000;">freelist</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">id</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">function</span> <span style="color: #000000;">fkd_new</span><span style="color: #0000FF;">(</span><span style="color: #004080;">sequence</span> <span style="color: #000000;">key_pairs</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">std</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">new_dict</span><span style="color: #0000FF;">(</span><span style="color: #000000;">key_pairs</span><span style="color: #0000FF;">),</span>
<span style="color: #000000;">cur</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">new_dict</span><span style="color: #0000FF;">(</span><span style="color: #000000;">std</span><span style="color: #0000FF;">),</span>
<span style="color: #000000;">id</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">freelist</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">id</span><span style="color: #0000FF;">=</span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">fkds</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">append</span><span style="color: #0000FF;">(</span><span style="color: #000000;">fkds</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">std</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">})</span>
<span style="color: #000000;">id</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">fkds</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">else</span>
<span style="color: #000000;">freelist</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">]</span>
<span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">std</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">}</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">id</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">fkd_clear</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">id</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">std</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">]</span>
<span style="color: #7060A8;">destroy_dict</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">][</span><span style="color: #000000;">CUR</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">new_dict</span><span style="color: #0000FF;">(</span><span style="color: #000000;">std</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">function</span> <span style="color: #000000;">fkd_get</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">id</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">object</span> <span style="color: #000000;">key</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">return</span> <span style="color: #7060A8;">getd</span><span style="color: #0000FF;">(</span><span style="color: #000000;">key</span><span style="color: #0000FF;">,</span><span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">][</span><span style="color: #000000;">CUR</span><span style="color: #0000FF;">])</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">fkd_set</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">id</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">object</span> <span style="color: #000000;">key</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">data</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">node</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">getd_index</span><span style="color: #0000FF;">(</span><span style="color: #000000;">key</span><span style="color: #0000FF;">,</span><span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">][</span><span style="color: #000000;">CUR</span><span style="color: #0000FF;">])</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">node</span><span style="color: #0000FF;">=</span><span style="color: #004600;">NULL</span> <span style="color: #008080;">then</span> <span style="color: #008080;">throw</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"invalid/new key"</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #7060A8;">setd</span><span style="color: #0000FF;">(</span><span style="color: #000000;">key</span><span style="color: #0000FF;">,</span><span style="color: #000000;">data</span><span style="color: #0000FF;">,</span><span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">][</span><span style="color: #000000;">CUR</span><span style="color: #0000FF;">])</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">fkd_remove</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">id</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">object</span> <span style="color: #000000;">key</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">std</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">],</span>
<span style="color: #000000;">node</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">getd_index</span><span style="color: #0000FF;">(</span><span style="color: #000000;">key</span><span style="color: #0000FF;">,</span><span style="color: #000000;">std</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">node</span><span style="color: #0000FF;">=</span><span style="color: #004600;">NULL</span> <span style="color: #008080;">then</span> <span style="color: #008080;">throw</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"invalid key"</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #7060A8;">setd</span><span style="color: #0000FF;">(</span><span style="color: #000000;">key</span><span style="color: #0000FF;">,</span><span style="color: #7060A8;">getd_by_index</span><span style="color: #0000FF;">(</span><span style="color: #000000;">node</span><span style="color: #0000FF;">,</span><span style="color: #000000;">std</span><span style="color: #0000FF;">),</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">function</span> <span style="color: #000000;">fkd_sprint</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">id</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">cur</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">fkds</span><span style="color: #0000FF;">[</span><span style="color: #000000;">id</span><span style="color: #0000FF;">][</span><span style="color: #000000;">CUR</span><span style="color: #0000FF;">]</span>
<span style="color: #004080;">sequence</span> <span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">getd_all_keys</span><span style="color: #0000FF;">(</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">res</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
<span style="color: #004080;">object</span> <span style="color: #000000;">ri</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">res</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]</span>
<span style="color: #000000;">res</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">ri</span><span style="color: #0000FF;">,</span><span style="color: #7060A8;">getd</span><span style="color: #0000FF;">(</span><span style="color: #000000;">ri</span><span style="color: #0000FF;">,</span><span style="color: #000000;">cur</span><span style="color: #0000FF;">)}</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">res</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">main</span><span style="color: #0000FF;">()</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">id</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">fkd_new</span><span style="color: #0000FF;">({{</span><span style="color: #008000;">"a"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">1</span><span style="color: #0000FF;">},{</span><span style="color: #008000;">"b"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">2</span><span style="color: #0000FF;">}})</span>
<span style="color: #0000FF;">?</span><span style="color: #000000;">fkd_sprint</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- {{"a",1},{"b",2}}</span>
<span style="color: #000000;">fkd_set</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"a"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">55</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">fkd_set</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"b"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">66</span><span style="color: #0000FF;">)</span>
<span style="color: #0000FF;">?</span><span style="color: #000000;">fkd_sprint</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- {{"a",55},{"b",66}}</span>
<span style="color: #000000;">fkd_clear</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">)</span>
<span style="color: #0000FF;">?</span><span style="color: #000000;">fkd_sprint</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- {{"a",1},{"b",2}}</span>
<span style="color: #000000;">fkd_set</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"a"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">55</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">fkd_set</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"b"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">66</span><span style="color: #0000FF;">)</span>
<span style="color: #0000FF;">?</span><span style="color: #000000;">fkd_get</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"a"</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- 55</span>
<span style="color: #000000;">fkd_remove</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"a"</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">try</span>
<span style="color: #000000;">fkd_set</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"NoNewKey"</span><span style="color: #0000FF;">,</span><span style="color: #000000;">77</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">catch</span> <span style="color: #000000;">e</span>
<span style="color: #0000FF;">?</span><span style="color: #000000;">e</span><span style="color: #0000FF;">[</span><span style="color: #004600;">E_USER</span><span style="color: #0000FF;">]</span> <span style="color: #000080;font-style:italic;">-- "invalid/new key"</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">try</span>
<span style="color: #0000FF;">?</span><span style="color: #000000;">fkd_sprint</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- {{"a",1},{"b",66}}</span>
<span style="color: #000000;">fkd_destroy</span><span style="color: #0000FF;">(</span><span style="color: #000000;">id</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #000000;">main</span><span style="color: #0000FF;">()</span>
<!--</syntaxhighlight>-->
 
=={{header|Python}}==
<langsyntaxhighlight lang="python">
from collections import UserDict
import copy
Line 243 ⟶ 924:
raise KeyError
else:
return super().setdefault(key, default)</langsyntaxhighlight>
 
=={{header|RubyRacket}}==
{{trans|D}}
{{in progress|lang=Ruby|day=15|month=February|year=2011}}
This task is implemented as a new fenced-hash time with an interface similar to the native hash. Also it can be used a native dict.
 
Implementation of functions that handle fenced-hash:
TODO: Write comments for FencedHash::new, FencedHash#delete and related methods. Add more methods (merge, merge!, reject, reject!, select, select!, update). Explain why FencedHash#replace and FencedHash#shift will not exist.
<syntaxhighlight lang="racket">
;(struct fenced-hash (actual original) ...)
 
(define (fenced-hash-ref dict
<lang ruby># fencedhash.rb
key
require 'forwardable'
[default (lambda () (error "key not found" key))])
(hash-ref (fenced-hash-actual dict) key default))
(define (fenced-hash-set! dict key val)
(unless (hash-has-key? (fenced-hash-actual dict) key)
(error "unable to add key" key))
(hash-set! (fenced-hash-actual dict) key val))
(define (fenced-hash-remove! dict key) ;reset the value!
(unless (hash-has-key? (fenced-hash-actual dict) key)
(error "key not found" key))
(hash-set! (fenced-hash-actual dict)
key
(hash-ref (fenced-hash-original dict) key)))
(define (fenced-hash-clear! dict) ;reset all values!
(hash-for-each (fenced-hash-original dict)
(lambda (key val) (hash-set! (fenced-hash-actual dict) key val))))
 
(define (fenced-hash-has-key? dict key)
# A FencedHash acts like a Hash, but with a fence around its keys.
(hash-has-key? (fenced-hash-actual dict) key))
# After the creation of a FencedHash, one cannot add nor remove keys.
(define (fenced-hash-count dict)
# Any attempt to insert a new key will raise KeyError. Any attempt to
(hash-count (fenced-hash-actual dict)))
# delete a key-value pair will keep the key but will reset the value to
# the default value.
class FencedHash < Object
extend Forwardable
include Enumerable
 
(define (fenced-hash-iterate-first dict)
#--
(hash-iterate-first (fenced-hash-actual dict)))
# @hash: our Hash inside the fence
(define (fenced-hash-iterate-next dict pos)
# @default_proc: passes self, not @hash
(hash-iterate-next (fenced-hash-actual dict) pos))
#++
(define (fenced-hash-iterate-key dict pos)
def_delegators(:@hash, :[], :assoc,
(hash-iterate-key (fenced-hash-actual dict) pos))
:compare_by_identity, :compare_by_identity?,
(define (fenced-hash-iterate-value dict pos)
:default, :empty?, :fetch, :flatten,
(hash-iterate-value (fenced-hash-actual dict) pos))
:has_key?, :has_value?, :hash, :include?,
:key, :key?, :keys, :length, :member?,
:rassoc, :size, :to_a,
:values, :values_at, :value?)
attr_reader :default_proc
 
(define (*fenced-hash-print dict port mode)
# Acts like Hash::[] but creates a FencedHash.
;private custom-write ;mode is ignored
def self.[](*args)
(write-string "#fenced-hash" port)
allocate.instance_eval do
(write (hash->list (fenced-hash-actual dict)) port))</syntaxhighlight>
@hash = Hash[*args]
self
end
end
 
Definition of the actual structure and a “public” creator:
# call-seq:
<syntaxhighlight lang="racket">(struct fenced-hash (actual original)
# FencedHash.new(obj=nil [,keys]) -> fh
#:extra-constructor-name *fenced-hash ;private constructor
# FencedHash.new([keys]) { |fh, key| block } -> fh
#:omit-define-syntaxes ;not sure this is a good idea
#
#:methods gen:custom-write
# Creates a FencedHash.....
[(define write-proc *fenced-hash-print)]
def initialize(*args, &block)
n = args.length
 
#:methods gen:dict
if block_given?
[(define dict-ref fenced-hash-ref)
raise ArgumentError, "wrong number of arguments" if n > 1
(define dict-set! fenced-hash-set!)
(define dict-remove! fenced-hash-remove!)
(define dict-has-key? fenced-hash-has-key?) ;unused in 5.6.3
(define dict-count fenced-hash-count)
(define dict-iterate-first fenced-hash-iterate-first)
(define dict-iterate-next fenced-hash-iterate-next)
(define dict-iterate-key fenced-hash-iterate-key)
(define dict-iterate-value fenced-hash-iterate-value)])
 
@default_proc = block
@hash = Hash.new { |hash, key| block[self, key] }
if n > 0
args[0].each { |key| @hash[key] = nil }
clear
end
else
raise ArgumentError, "wrong number of arguments" if n > 2
 
(define (fenced-hash . args) ; public constructor
default = if n > 0 then n[0] else nil end
(define original (apply @hash = Hash.new(defaultargs))
(*fenced-hash (hash-copy original) original))</syntaxhighlight>
if n > 1
args[1].each { |key| @hash[key] = default }
end
end
end
 
'''Example:''' Use the fenced-hash functions:
def initialize_copy(orig)
<syntaxhighlight lang="racket">(define d (fenced-hash "a" 1 "b" 2))
super
@hash = @hash.dup
end
 
(displayln d)
# Clears all values. For each key-value pair, this retains the key
(fenced-hash-set! d "a" 55)
# but resets the value to default.
(fenced-hash-set! d "b" 66)
#--
(displayln d)
# The line "@hash = @hash" checks that _self_ is not frozen, because
(fenced-hash-clear! d)
# Object#freeze only freezes _self_ and not @hash.
(displayln d)
#++
(fenced-hash-set! d "a" 55)
def clear
(fenced-hash-set! d "b" 66)
@hash = @hash
(displayln d)
@hash.each_key { |key| delete key }
(fenced-hash-remove! d "a")
self
(displayln d)</syntaxhighlight>
end
{{out}}
<pre>#fenced-hash(("b" . 2) ("a" . 1))
#fenced-hash(("b" . 66) ("a" . 55))
#fenced-hash(("b" . 2) ("a" . 1))
#fenced-hash(("b" . 66) ("a" . 55))
#fenced-hash(("b" . 66) ("a" . 1))</pre>
 
'''Example (continued):''' Use the same object as a dict. The dict-clear! method is not defined, so we must call fenced-hash-clear! instead.
# .....
<syntaxhighlight lang="racket">(fenced-hash-clear! d)
def default=(obj)
(displayln d)
@default_proc = nil
(dict-set! d "a" 55)
@hash.default = obj
(dict-set! d "b" 66)
end
(displayln d)
(fenced-hash-clear! d) ;dict-clear is not defined
(displayln d)
(dict-set! d "a" 55)
(dict-set! d "b" 66)
(displayln d)
(dict-remove! d "a")
(displayln d)</syntaxhighlight>
{{out}}
<pre>#fenced-hash(("b" . 2) ("a" . 1))
#fenced-hash(("b" . 66) ("a" . 55))
#fenced-hash(("b" . 2) ("a" . 1))
#fenced-hash(("b" . 66) ("a" . 55))
#fenced-hash(("b" . 66) ("a" . 1))</pre>
 
=={{header|Raku}}==
# .....
(formerly Perl 6)
def default_proc=(proc_obj)
{{Works with|rakudo|2016.08}}
# Convert _proc_obj_ to a block parameter.
Here we use delegation to handle all the normal hash methods that we don't need to override to define our new class.
proc_obj = proc &proc_obj
<syntaxhighlight lang="raku" line>class FixedHash {
has $.hash handles *;
method new(*@args) { self.bless: hash => Hash.new: @args }
method AT-KEY(FixedHash:D: $key is copy) is rw {
$!hash.EXISTS-KEY($key) ?? $!hash.AT-KEY($key) !! Failure.new(q{can't store value for unknown key});
}
method DELETE-KEY($key) { $!hash.{$key} = Nil }
}
 
# Testing
@hash.default_proc = proc { |hash, key| proc_obj[self, key] }
my $fh = FixedHash.new: "a" => 1, "b" => 2;
@default_proc = proc_obj
say $fh<a b>; # 1 2
end
$fh<b>:delete;
say $fh<a b>; # 1 Nil
$fh<b> = 42;
say $fh<a b>; # 1 42
say $fh<c>; # Nil
$fh<c> = 43; # error
</syntaxhighlight>
{{out}}
<pre>(1 2)
(1 (Any))
(1 42)
can't store value for unknown key
in block <unit> at native-demonstration.p6:17
 
Actually thrown at:
# Deletes the value of the key-value pair for _key_.
in block <unit> at native-demonstration.p6:17</pre>
#
# If _key_ is in the fence.....
def delete(key)
@hash = @hash
 
By defining [http://design.raku.org/S12.html#FALLBACK_methods FALLBACK] any class can handle undefined method calls. Since any class inherits plenty of methods from <tt>Any</tt> our magic object will be more of a novice conjurer then a master wizard proper.
begin
original_value = @hash.fetch(key)
rescue IndexError
# _key_ is not in the fence.
if block_given?
yield key
else
nil
end
else
# _key_ is in the fence.
if @default_proc
@default_proc[self, key]
else
@hash[key] = @hash.default
end
original_value
end
end
 
<syntaxhighlight lang="raku" line>class Magic {
# .....
has %.hash;
def delete_if
multi method FALLBACK($name, |c) is rw { # this will eat any extra parameters
return enum_for(:delete_if) unless block_given?
%.hash{$name}
}
 
multi method FALLBACK($name) is rw {
@hash = @hash
%.hash{$name}
@hash.each { |key, value| delete key if yield key, value }
self }
}
end
 
my $magic = Magic.new;
# Yields each key-value pair to the block, or returns an enumerator.
$magic.foo = 10;
# Acts like Hash#each.
say $magic.foo;
def each &block # :yields: key, value
$magic.defined = False; # error</syntaxhighlight>
return enum_for(:each) unless block
@hash.each &block
end
alias each_pair each
 
{{output}}
# Yields each key to the block, or returns an enumerator.
<pre>10
# Acts like Hash#each_key.
Cannot modify an immutable Bool
def each_key &block # :yields: key
in block <unit> at native-demonstration.p6:15</pre>
return enum_for(:each_key) unless block
@hash.each_key &block
end
 
=={{header|Ring}}==
# Yields each value to the block, or returns an enumerator.
<syntaxhighlight lang="ring">
# Acts like Hash#each_value.
# Project : Create an object/Native demonstration
def each_value &block # :yields: value
return enum_for(:each_value) unless block
@hash.each_value &block
end
 
map = []
# Returns true if _other_ is a FencedHash and has the same key-value
map["A"] = 65
# pairs as _self_. Acts like Hash#eql?.
map["B"] = 66
#--
map["C"] = 67
# Consistent with FencedHash#hash because it delegates to @hash.hash.
see map #++ nl
</syntaxhighlight>
def eql?(other)
Output:
FencedHash === other and
<pre>
@hash.eql?(other.instance_eval { @hash })
A
end
65
B
66
C
67
</pre>
 
=={{header|Ruby}}==
# Returns true if _other_ is a FencedHash and if the key-value pairs
{{works with|Ruby|1.9}}
# of _self_ equal those of _other_. Acts like Hash#==.
<syntaxhighlight lang="ruby"># A FencedHash acts like a Hash, but with a fence around its keys.
def ==(other)
# One may change its values, but not its keys. Any attempt to insert
FencedHash === other and
# a new key raises KeyError. One may delete a key, but this only
@hash == (other.instance_eval { @hash })
# restores its original value.
end
#
 
# FencedHash reimplements these Hash methods: #[] #[]= #clear #delete
# .....
# #delete_if #default #default= #each_key #each_pair #each_value
def keep_if
# #fetch #has_key? #keep_if #keys #length #values #values_at
return enum_for(:keep_if) unless block_given?
class FencedHash
 
@hash = @hash
@hash.each { |key, value| delete key unless yield key, value }
self
end
 
# call-seq:
# Stores a _value_ for a _key_. This only works if _key_ is in the
# fence; FencedHash prevents the insertion of .new(hash, keys.obj=nil) If _key_-> isfh
#
# not in the fence, then this method raises KeyError.
# Creates a FencedHash that takes its keys and original values from
def store(key, value)
# a source _hash_. The source _hash_ can be any object that
@hash = @hash
# responds to each_pair. Sets the default value for missing keys to
if @hash.has_key? key
# _obj_, so FencedHash#[] returns _obj_ when a key is not in fence.
@hash.store(key, value)
def initialize(hash, obj=nil)
else
@default = obj
c = if defined? KeyError then KeyError else IndexError end
@hash = {}
raise c, "fence prevents new key: #{key}"
hash.each_pair do |key, value|
# @hash[key][0] = current value
# @hash[key][1] = original value
@hash[key] = [value, value]
end
end
alias []= store
 
def initialize_clone(orig)
# Converts _self_ to a regular Hash. Returns a new Hash that has the
# Object#clone calls here in Ruby 2.0. If _orig_ was frozen, then
# same key-value pairs as _self_.
# each array of _values_ is frozen, so make frozen clones.
def to_hash
@hash.dupsuper
copy = {}
@hash.each_pair {|key, values| copy[key] = values.clone }
@hash = copy
end
 
def initialize_dup(orig)
# Converts _self_ to a String.
# Object#dup calls here in Ruby 2.0. If _orig_ was frozen, then
def to_s
# make duplicates that are not frozen.
"#<#{self.class}: #{@hash.inspect}>"
super
copy = {}
@hash.each_pair {|key, values| copy[key] = values.dup }
@hash = copy
end
alias inspect to_s
end</lang>
 
# Retrieves current value for _key_, like Hash#[]. If _key_ is not
<lang ruby># fh-test.rb
# in fence, returns default object.
require 'fencedhash'
def [](key)
require 'test/unit'
values = @hash[key]
 
if values
class TestFencedHash < Test::Unit::TestCase
values[0]
if RUBY_VERSION >= "1.9"
else
KeyEx = KeyError
FrozenEx = RuntimeError@default
else end
KeyEx = IndexError
FrozenEx = TypeError
end
 
# call-seq:
def setup
# @fh[key] = FencedHash[:qvalue => 11, :w => 22, :e =-> 33,value
# :r => 44fh.store(key, :t => 55,value) :y =-> 66]value
#
# Sets _value_ for a _key_. Returns _value. If _key_ is not in
# fence, raises KeyError.
def []=(key, value)
values = @hash[key]
if values
values[0] = value
else
raise KeyError, "fence prevents adding new key: #{key.inspect}"
end
end
alias store []=
 
# Resets all keys to their original values. Returns self.
def test_bracket_operator
def clear
assert_equal 11, @fh[:q]
@hash.each_value {|values| values[0] = values[1]}
assert_equal 22, @fh[:w]
self
assert_equal 33, @fh[:e]
assert_equal 44, @fh[:r]
assert_equal 55, @fh[:t]
assert_equal 66, @fh[:y]
assert_nil @fh[:u]
end
 
# Resets _key_ to its original value. Returns old value before
def test_delete
# reset. If _key_ is not in fence, returns +nil+.
assert_equal 44, (@fh.delete :r)
def delete(key)
assert_nil @fh.fetch(:r)
assert_nilvalues = @fh.delete(:r)hash[key]
if values
assert_nil @fh.delete(:u)
@fh[:r] old = "replacement"values[0]
values[0] = values[1]
assert_equal "replacement", (@fh.delete :r)
old # return old
end # else return nil
end
 
# call-seq:
def test_delete_if
# a = @fh.delete_if { |key, value| keyblock ==} :t ||-> value == 66 }fh
# fh.delete_if -> enumerator
assert_same @fh, a
#
assert_equal 2, @fh.values.grep(nil).length
# Yields each _key_ with current _value_ to _block_. Resets _key_
@fh[:y] = "why?"
# to its original value when block evaluates to true.
@fh[:t] = "tea!"
def delete_if
assert_equal 0, @fh.values.grep(nil).length
if block_given?
@hash.each_pair do |key, values|
yield(key, values[0]) and values[0] = values[1]
end
self
else
enum_for(:delete_if) { @hash.size }
end
end
 
# The default value for keys not in fence.
def test_default
attr_accessor :default
fruit = FencedHash.new(0, [:apple, :banana, :cranberry])
assert_equal [0, 0, 0], fruit.values
fruit[:apple] += 1
fruit[:banana] += 5
fruit[:cranberry] *= 5
assert_equal 1, fruit[:apple]
assert_equal 5, fruit[:banana]
assert_equal 0, fruit[:cranberry]
assert_equal 0, fruit.default
end
 
# call-seq:
def test_default_assign
# fh.each_key {|key| block} -> fh
assert_nil @fh.default
# fh.each_key -> enumerator
@fh.delete :w
#
 
# Yields each key in fence to the block.
@fh.default = -1
def each_key(&block)
assert_equal -1, @fh.default
@fh.deleteif :eblock
@hash.each_key(&block)
 
assert_nil @fh[:w] self
else
assert_equal -1, @fh[:e]
enum_for(:each_key) { @hash.size }
end
end
 
# call-seq:
def test_default_proc
# fh.each_pair {|key, value| block} -> fh
count = 0
# fh.each_pair -> enumerator
fruit = FencedHash.new([:apple, :banana, :cranberry]) do |h, k|
#
if h.key? k then h[k] = [] else count += 1 end
# Yields each key-value pair to the block, like Hash#each_pair.
# This yields each [key, value] as an array of 2 elements.
def each_pair
if block_given?
@hash.each_pair {|key, values| yield [key, values[0]] }
self
else
enum_for(:each_pair) { @hash.size }
end
fruit[:apple].push :red
fruit[:banana].concat [:green, :yellow]
fruit[:cranberry].push :red
assert_equal 1, fruit[:orange]
assert_equal [:red], fruit[:apple]
assert_equal [:green, :yellow], fruit[:banana]
assert_equal [:red], fruit.delete(:cranberry)
assert_equal 2, fruit[:orange]
assert_equal [], fruit[:cranberry]
assert_nil fruit.delete(:orange)
assert_equal 3, fruit[:orange]
assert_equal [], fruit.default_proc[FencedHash[1 => 2], 1]
end
 
# call-seq
def test_each
# fh.each_value {|value| block} -> fh
count = 0
# fh.each_value -> enumerator
@fh.each do |key, value|
#
assert_kind_of Symbol, key
# Yields current value of each key-value pair to the block.
assert_kind_of Integer, value
def each_value
assert_equal true, (@fh.has_key? key)
if block_given?
assert_equal true, (@fh.has_value? value)
@hash.each_value {|values| yield values[0] }
count += 1
else
enum_for(:each_value) { @hash.size }
end
assert_equal 6, count
end
 
# call-seq:
def test_eql?
# fenhsh.fetch(key [,default])
other = FencedHash[:r, 44, :t, 55, :y, 66,
# fenhsh.fetch(key) {|key| block }
:q, 11, :w, 22, :e, 33]
#
float = FencedHash[:y, 66.0, :t, 55.0, :r, 44.0,
# Fetches value for _key_. Takes same arguments as Hash#fetch.
:e, 33.0, :w, 22.0, :q, 11.0]
def fetch(*argv)
tt = [true, true]
ffargc = [false, false]argv.length
unless argc.between?(1, 2)
 
raise(ArgumentError,
if RUBY_VERSION >= "1.9"
"wrong number of arguments (#{argc} for 1..2)")
assert_equal tt, [(@fh.eql? other), (other.eql? @fh)]
end
assert_equal ff, [(@fh.eql? float), (float.eql? @fh)]
if argc == 2 and block_given?
assert_equal ff, [(other.eql? float), (float.eql? other)]
warn("#{caller[0]}: warning: " +
"block supersedes default value argument")
end
 
key, default = argv
assert_equal tt, [@fh == other, other == @fh]
values = @hash[key]
assert_equal tt, [@fh == float, float == @fh]
if values
assert_equal tt, [other == float, float == other]
values[0]
 
helsif = @fh.to_hashblock_given?
if RUBY_VERSION >=yield "1.9"key
elsif argc == 2
assert_equal ff, [(@fh.eql? h), (h.eql? @fh)]
default
else
raise KeyError, "key not found: #{key.inspect}"
end
assert_equal ff, [@fh == h, h == @fh]
end
 
# Freezes this FencedHash.
def test_fetch
def freeze
assert_equal 11, @fh.fetch(:q)
@hash.each_value {|values| values.freeze }
assert_equal 22, @fh.fetch(:w)
super
assert_equal 33, @fh.fetch(:e)
assert_equal 44, @fh.fetch(:r)
assert_equal 55, @fh.fetch(:t)
assert_equal 66, @fh.fetch(:y)
assert_raises(KeyEx) { @fh.fetch :u }
end
 
# Returns true if _key_ is in fence.
def test_freeze
def has_key?(key)
assert_equal false, @fh.frozen?
@fhhash.freezehas_key?(key)
 
2.times do
assert_equal true, @fh.frozen?
assert_raises(FrozenEx) { @fh.clear }
assert_raises(FrozenEx) { @fh.delete :q }
assert_raises(FrozenEx) { @fh.delete_if { true } }
assert_raises(FrozenEx) { @fh.keep_if { false } }
assert_raises(FrozenEx) { @fh.store :w, "different" }
assert_raises(FrozenEx) { @fh[:w] = "different" }
 
# Repeat the tests with a clone. The clone must be frozen.
@fh = @fh.clone
end
 
# A duplicate is not frozen.
@fh = @fh.dup
assert_equal false, @fh.frozen?
@fh[:w] = "different"
assert_equal "different", @fh[:w]
end
alias include? has_key?
alias member? has_key?
 
# call-seq:
def test_has_key
# fh.keep_if {|key, value| block } -> fh
2.times do |t|
# fh.keep_if -> enumerator
assert_equal true, (@fh.has_key? :y)
#
assert_equal true, (@fh.include? :y)
# Yields each _key_ with current _value_ to _block_. Resets _key_
assert_equal true, (@fh.key? :y)
# to its original value when block evaluates to false.
assert_equal true, (@fh.member? :y)
def keep_if
 
if block_given?
assert_equal false, (@fh.has_key? :u)
@hash.each_pair do |key, values|
assert_equal false, (@fh.include? :u)
yield(key, values[0]) or values[0] = values[1]
assert_equal false, (@fh.key? :u)
end
assert_equal false, (@fh.member? :u)
self
 
else
# Repeat the tests.
enum_for(:keep_if) { @hash.size }
# The fence must prevent any changes to the keys.
@fh.delete :y
(@fh[:u] = "value") rescue "ok"
end
end
 
# Returns array of keys in fence.
def test_has_value
def keys
assert_equal true, (@fh.has_value? 22)
@hash.keys
assert_equal true, (@fh.value? 22)
 
assert_equal false, (@fh.has_value? 4444)
assert_equal false, (@fh.value? 4444)
end
 
# Returns number of key-value pairs.
def test_inject
def length
# To get an :inject method, FencedHash should mix in Enumerable.
@hash.length
assert_kind_of Enumerable, @fh
assert_equal 231, @fh.inject(0) { |sum, kv| sum + kv[1] }
end
alias size length
 
# Converts self to a regular Hash.
def test_keep_if
def to_h
a = @fh.keep_if { |key, value| key == :t || value == 66 }
result = Hash.new(@default)
assert_same @fh, a
assert_equal@hash.each_pair 4{|key, @fh.values.grep(nil).length| result[key] = values[0]}
@fh.delete :yresult
@fh.delete :t
assert_equal 6, @fh.values.grep(nil).length
end
 
# Converts self to a String.
def test_keys
def to_s
assert_equal([:e, :q, :r, :t, :w, :y],
"#<#{self.class}: #{to_h}>"
@fh.keys.sort_by { |o| o.to_s })
end
alias inspect to_s
 
# Returns array of current values.
def test_length
def values
assert_equal 6, @fh.length
@hash.each_value.map {|values| values[0]}
assert_equal 6, @fh.size
end
 
# Returns array of current values for keys, like Hash#values_at.
def test_store
def values_at(*keys)
assert_raises(KeyEx) { @fh[:a] = 111 }
keys.map {|key| self[key]}
assert_equal 222, (@fh[:e] = 222)
assert_equal 222, (@fh.fetch :e)
assert_equal 333, @fh.store(:e, 333)
assert_equal 333, @fh[:e]
end
end</syntaxhighlight>
 
=={{header|Scala}}==
def test_values
{{Out}}Best seen running in your browser either by [https://scalafiddle.io/sf/OuVZ3bT/0 ScalaFiddle (ES aka JavaScript, non JVM)] or [https://scastie.scala-lang.org/qW5qzmdKSZSyAbZEqDROoA Scastie (remote JVM)].
assert_equal [11, 22, 33, 44, 55, 66], @fh.values.sort!
<syntaxhighlight lang="scala">object CreateMapObject extends App {
end
val map = Map('A' -> 65, 'B' -> 66, 'C' -> 67)
 
println(map)
if RUBY_VERSION >= "1.8.7"
}</syntaxhighlight>
def test_delete_if_enum
a = @fh.delete_if.with_index { |kv, i| i >= 2 }
assert_same @fh, a
assert_equal 4, @fh.values.grep(nil).length
end
 
=={{header|Tcl}}==
def test_keep_if_enum
This solution uses a dict(ionary), so requires Tcl 8.5 or better. Variable traces are used to detect write or unset access to such a protected variable, restore it to the backup value at protection time, and throw an exception
a = @fh.keep_if.with_index { |kv, i| i >= 2 }
assert_same @fh, a
assert_equal 2, @fh.values.grep(nil).length
end
end
 
<syntaxhighlight lang="tcl">proc protect _var {
if RUBY_VERSION >= "1.9"
upvar 1 $_var var
def test_class_bracket_operator
trace add variable var {write unset} [list protect0 $var]
from_pairs = FencedHash[10, "ten", 20, "twenty", 30, "thirty"]
}
from_alist = FencedHash[ [ [10, "ten"], [20, "twenty"], [30, "thirty"] ] ]
proc protect0 {backup name1 name2 op} {
from_hash = FencedHash[10 => "ten", 20 => "twenty", 30 => "thirty"]
upvar 1 $name1 var
from_fhash = FencedHash[from_pairs]
trace remove variable var {write unset} [list protect 0 $backup]
set var $backup
trace add variable var {write unset} [list protect0 $backup]
return -code error "$name1 is protected"
}
proc trying cmd { #-- convenience function for demo
puts "trying: $cmd"
if [catch {uplevel 1 $cmd} msg] {puts $msg}
}</syntaxhighlight>
Testing:
dict set dic 1 one
dict set dic 2 two
puts dic:$dic
protect dic
trying "dict set dic 3 three"
puts dic:$dic
trying "dict unset dic 1"
trying "unset dic"
puts dic:$dic
 
displays on stdout:
[from_pairs, from_alist, from_hash, from_fhash, from_pairs
dic:1 one 2 two
].each_cons(2) do |a, b|
trying: dict set dic 3 three
assert_equal a, b
can't set "dic": dic is protected
assert_not_same a, b
dic:1 one 2 two
end
trying: dict unset dic 1
end
can't set "dic": dic is protected
trying: unset dic
dic:1 one 2 two
 
=={{header|Wren}}==
def test_default_proc_assign
<syntaxhighlight lang="wren">class FixedSizeMap {
assert_nil @fh.default_proc
construct new(map) {
p = @fh.default_proc = proc { |h, k| h[k] = :deleted }
// copy the map so it cannot be mutated from the original reference
assert_same p, @fh.default_proc
_map = {}
for (me in map.toList) _map[me.key] = me.value
}
 
containsKey(key) { _map[key] != null }
assert_equal 11, @fh.delete(:q)
assert_equal :deleted, @fh[:q]
assert_raises(KeyEx) { @fh[:u] }
 
count { @fh_map.defaultcount = :value}
assert_nil @fh.default_proc
@fh.default_proc = p
assert_nil @fh.default
end
 
keys { _map.keys }
def test_each_rewind
 
class << @fh
values { _map.values }
attr_reader :test_rewind
 
def rewind
[key] { _map[key] }
@test_rewind = "correct"
[key] =(value) { end
// do nothing if key doesn't already exist
end
if (_map[key] != null) _map[key] = value
assert_nil @fh.test_rewind
}
 
reset(key) {
var t = _map[key].type
// leave unaltered if no suitable default value
_map[key] = (t == Num) ? 0 :
(t == String) ? "":
(t == Bool) ? false :
(t == List) ? [] :
(t == Map) ? {} : _map[key]
}
 
iterate(iterator) { _map.iterate(iterator) }
iteratorValue(iterator) { _map.iteratorValue(iterator) }
 
toString { _map.toString }
}
 
var map = { "a": 1, "b": 2 }
var fsm = FixedSizeMap.new(map)
System.print(fsm)
System.print(fsm.count)
fsm["a"] = 3
fsm["b"] = 4
System.print(fsm)
System.print(fsm.containsKey("c"))
fsm["c"] = 5 // attempt to add a new key/value pair
System.print(fsm) // ignored
fsm.reset("a")
System.print(fsm)
System.print(fsm.keys.toList)
System.print(fsm.values.toList)
for (me in fsm) System.print([me.key, me.value])
</syntaxhighlight>
 
{{out}}
<pre>
{b: 2, a: 1}
2
{b: 4, a: 3}
false
{b: 4, a: 3}
{b: 4, a: 0}
[b, a]
[4, 0]
[b, 4]
[a, 0]
</pre>
 
=={{header|zkl}}==
zkl has two dictionary objects: SD, a small dictionary that is created immutable and the "regular" dictionary has has a makeReadOnly method. They both behave the same when locked down.
<syntaxhighlight lang="zkl">d:=SD("one",1,"two",2);
d.keys; //-->L("one","two")
d["one"]; //-->1
d.add("three",3); // error thrown
d.pop("one") // error thrown</syntaxhighlight>
 
# @fh.each.rewind must call @fh.rewind. If @fh forwards :each
# to another object then this test fails.
@fh.each.rewind
assert_equal "correct", @fh.test_rewind
end
 
def test_insertion_order
assert_equal [:q, :w, :e, :r, :t, :y], @fh.keys
assert_equal [11, 22, 33, 44, 55, 66], @fh.values
end
 
def test_key
assert_equal :q, @fh.key(11)
assert_equal :w, @fh.key(22)
assert_equal :e, @fh.key(33)
assert_equal :r, @fh.key(44)
assert_equal :t, @fh.key(55)
assert_equal :y, @fh.key(66)
assert_nil @fh.key(77)
end
end
end</lang>
 
{{omit from|AWK|Cannot tie the []= operator nor the delete command to custom functions.}}
Line 756 ⟶ 1,489:
{{omit from|C|No associative arrays.}}
{{omit from|dc|No associative arrays.}}
{{omit from|Go|No operator overriding.}}
{{omit from|GUISS}}
{{omit from|PureBasic}}
{{omit from|sed|No associative arrays.}}
{{omit from|UNIX Shell|Bourne shell does not have these, but bashisms may be available on some shells}}
{{omit from|Tcl|The value system and object system do not interact in a way that is necessary to support the prerequisites of this task. In particular, native dicts and arrays are not objects, and objects formally occupy part of the space of functions and not values or variables.}}
{{omit from|PicoLisp|Can't change the behavior of the property system without changing the language around it.}}
PureFox
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