Work with Associative Arrays

Using JSL, you can find, add, or delete keys in an associative array.

Find the Number of Keys

To determine the number of keys that an associative array contains, use the N Items() function.

cary = Associative Array();

cary["state"] = "NC";

cary["population"] = 116234;

cary["weather"] = "cloudy";

cary["population"] += 10;

cary["weather"] = "sunny";

cary["high schools"] = {"Cary", "Green Hope", "Panther Creek"};

N Items( cary );

4

Add and Delete Keys and Values

To add or delete key-value pairs from an associative array, use the following functions:

• Insert()

• Insert Into()

• Remove()

• Remove From()

Notes:

• Insert() and Remove() return a named copy of the given associative array with the key-value pair added or removed.

• Insert Into() and Remove From() add or remove the key-value pairs directly from the given associative array.

• Insert() and Insert Into() take three arguments: the associative array, a key, and a value.

• Remove() and Remove From() take two arguments: the associative array and a key.

• If you insert a key with no value provided, the key is assigned a value of 1.

Examples

The following examples illustrate Insert() and Insert Into():

cary = Associative Array();

cary["state"] = "NC";

cary["population"] = 116234;

cary["weather"] = "cloudy";

cary["population"] += 10;

cary["weather"] = "sunny";

cary["high schools"] = {"Cary", "Green Hope", "Panther Creek"};

newcary = Insert( cary, "time zone", "Eastern" );

Show( cary, newcary );

cary = ["high schools" => {"Cary", "Green Hope", "Panther Creek"}, "population" => 116244, "state" => "NC", "weather" => "sunny"];

newcary = ["high schools" => {"Cary", "Green Hope", "Panther Creek"}, "population" => 116244, "state" => "NC", "time zone" => "Eastern", "weather" => "sunny"];

cary = Associative Array();

cary["state"] = "NC";

cary["population"] = 116234;

cary["weather"] = "cloudy";

cary["population"] += 10;

cary["weather"] = "sunny";

cary["high schools"] = {"Cary", "Green Hope", "Panther Creek"};

Insert Into(cary, "county", "Wake");

Show( cary );

cary = ["county" => "Wake", "high schools" => {"Cary", "Green Hope", "Panther Creek"}, "population" => 116244, "state" => "NC", "weather" => "sunny"];

Note that cary <<Insert is a message sent to an associative array that does the same thing as the function Insert Into(). For example, these two statements are equivalent:

cary << Insert( "county", "Wake" );

Insert Into( cary, "county", "Wake" );

The following examples illustrate Remove() and Remove From():

cary = Associative Array();

cary["state"] = "NC";

cary["population"] = 116234;

cary["weather"] = "cloudy";

cary["population"] += 10;

cary["weather"] = "sunny";

cary["high schools"] = {"Cary", "Green Hope", "Panther Creek"};

newcary = Remove( cary, "high schools" );

Show( cary, newcary );

cary = ["high schools" => {"Cary", "Green Hope", "Panther Creek"}, "population" => 116244, "state" => "NC", "weather" => "sunny"];

newcary = ["population" => 116244, "state" => "NC", "weather" => "sunny"];

Remove From( cary, "weather" );

Show( cary );

cary = ["high schools" => {"Cary", "Green Hope", "Panther Creek"}, "population" => 116244, "state" => "NC", "weather" => "sunny"];

newcary = ["population" => 116244, "state" => "NC", "weather" => "sunny"];

cary = ["high schools" => {"Cary", "Green Hope", "Panther Creek"}, "population" => 116244, "state" => "NC"];

Note that aa << Remove is a message sent to an associative array that does the same thing as the function Remove From(). For example, these two statements are equivalent:

cary << Remove( "weather" );

Remove From( cary, "weather" );

Find Keys or Values in an Associative Array

To determine whether a certain key is contained within an associative array, use the Contains() function.

cary = Associative Array();

cary["state"] = "NC";

cary["population"] = 116234;

cary["weather"] = "cloudy";

cary["population"] += 10;

cary["weather"] = "sunny";

cary["high schools"] = {"Cary", "Green Hope", "Panther Creek"};

Contains(cary, "high schools");

1

Contains(cary, "lakes");

0

To obtain a list of all keys contained in an associative array, use the << Get Keys message.

cary << Get Keys;

{"high schools", "population", "state", "weather"}

To obtain a list of all values contained in an associative array, use the <<Get Values message.

cary << Get Values;

{{"Cary", "Green Hope", "Panther Creek"}, 116244, "NC", "sunny"}

If you want to see only the values for certain keys, you can specify them as arguments. The keys must be given as a list.

cary << Get Values({"state", "population"});

{"NC", 116244}

To see a value for a single key, use the <<Get Value message. Specify only one key and do not place it in a list.

cary << Get Value("weather");

"sunny"

To obtain a list of all key-value pairs in an associative array, use the <<Get Contents message.

cary << Get Contents;

{{"high schools", {"Cary", "Green Hope", "Panther Creek"}},

{"population", 116244},

{"state", "NC"},

{"weather", "sunny"}}

Note: Using the <<Get Contents message, the returned list does not include the default value. Keys are listed alphabetically.

Iterate through an Associative Array

To iterate through as associative array, use the <<First and <<Next messages. <<First returns the first key in the associative array. <<Next(key) returns the key that follows the key that is given as the argument.

The following example removes all key-value pairs from the associative array cary, leaving an empty associative array:

currentkey = cary << First;

total = N Items( cary );

For( i = 1, i <= total, i++,

	nextkey = cary << Next( currentkey );

	Remove From( cary, currentkey );

	currentkey = nextkey;

);

Show( cary );

cary = [=>];

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