Maps in Scilab

Maps are Scilab’s built-in associative data type (sometimes called hashes or dicts in other languages).

To create an empty map, use the mlist function.

m = mlist(['keys', 'vals'], [], []);

Set key/value pairs using typical name(key) = val syntax.

m.keys($ + 1) = 'k1';
m.vals($ + 1) = 7;
m.keys($ + 1) = 'k2';
m.vals($ + 1) = 13;

Printing a map with disp will show all of its key/value pairs.

disp(m);

Get a value for a key with its index.

index = find(m.keys == 'k1');
v1 = m.vals(index);
disp('v1: ' + string(v1));

If the key doesn’t exist, the zero value (e.g., 0 for integers) of the value type is returned.

index = find(m.keys == 'k3');
if isempty(index) then
    v3 = 0;
else
    v3 = m.vals(index);
end
disp('v3: ' + string(v3));

The size function returns the number of key/value pairs when called on a map.

len = length(m.keys);
disp('len: ' + string(len));

To remove key/value pairs from a map, use appropriate indexing.

index = find(m.keys == 'k2');
m.keys(index) = [];
m.vals(index) = [];
disp(m);

To remove all key/value pairs from a map, simply clear the lists.

m.keys = [];
m.vals = [];
disp(m);

The second return value when getting a value from a map indicates if the key was present in the map.

index = find(m.keys == 'k2');
prs = ~isempty(index);
disp('prs: ' + string(prs));

You can also declare and initialize a new map in the same line with this syntax.

n = mlist(['keys', 'vals'], ['foo', 'bar'], [1, 2]);
disp(n);

Note that maps appear in the form [keys:values] when printed with disp.

if equals(n.vals, [1, 2]) then
    disp('n == n2');
end

--> disp(m)
 keys: ["k1" "k2"]
 vals: [7 13]

--> disp('v1: ' + string(v1))
v1: 7

--> disp('v3: ' + string(v3))
v3: 0

--> disp('len: ' + string(len))
len: 2

--> disp(m)
 keys: ["k1"]
 vals: [7]

--> disp(m)
 keys: []
 vals: []

--> disp('prs: ' + string(prs))
prs: F

--> disp(n)
 keys: ["foo" "bar"]
 vals: [1 2]

--> disp('n == n2')
n == n2