On subsequent appearances, the reader simply uses the existing symbol. EQ is not guaranteed to be true for identical characters or numbers. Like EQL , the comparison of characters within strings is case-sensitive. This kind of test typically compiles into one or two machine instructions and is very fast. If you know the type of your data in advance, you can use comparisons that are specialized to test that particular type of data.
Tests are available for characters, strings, lists, and numbers.
And, of course, there are also comparisons for other relationships besides equality. This book may not be reproduced without the written consent of its author. Online distribution is restricted to the author's site.