MATLAB COMPILER RELEASE NOTES User's Guide download pdf (Page 433)

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Programming Fundamentals

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Programming Fundamentals

Fast Key Lookup Provided with New Map Data Structure

This release introduces a new MATLAB class called a Map. An object of the Map class is

an array of any MATLAB data type that supports lookup table functionality. Unlike most

arrays in MATLAB that only allow access to the elements by means of integer indices,

indices for Map containers can be nearly any scalar numeric value or a character string.

The following example creates a Map object that is an array of strings. It is very much

like any other string array except that with each value of this array there is also a lookup

key associated with it. This particular Map contains the names of capital cities in the

United States. These are the values of the Map object. Associated with each capital city

value is the US state that it resides in. These are the keys of the Map object. You look

up values in the Map using key indices. Call the containers.Map constructor to create an

array of six capital cities indexed by six US states. (The capital of Alaska has purposely

been entered incorrectly):

US_Capitals = containers.Map( ...

{'Arizona', 'Nebraska', 'Nevada', ... % 6 States

'New York', 'Georgia', 'Alaska'}, ...

{'Phoenix', 'Lincoln', 'Carson City', ... % 6 Capitals

'Albany', 'Atlanta', 'Fairbanks'});

Show the capitals of three of the states by looking them up in the Map using the string

indices 'Nevada', 'Alaska' and 'Georgia':

values(US_Capitals, {'Nevada', 'Alaska', 'Georgia'})

ans =

'Carson City' 'Fairbanks' 'Atlanta'

Correct the capital city of Alaska by overwriting the entry at string index 'Alaska':

US_Capitals('Alaska') = 'Juneau';

US_Capitals('Alaska')

ans =

Juneau

The term containers.Map refers to a Map class that is part of a MATLAB package

called containers. For more information, see Map Containers in the Programming

Fundamentals documentation.

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