Sequences and laziness

 

"A seq is like a logical cursor."

 
 --Rich Hickey

Sequences (commonly known as seqs) are a way to sequentially consume a succession of data. As with iterators, they let a user begin consuming elements from the head and proceed realizing one element after another. However, unlike iterators, sequences are immutable. Also, since sequences are only a view of the underlying data, they do not modify the storage structure of the data.

What makes sequences stand apart is they are not data structures per se; rather, they are a data abstraction over a stream of data. The data may be produced by an algorithm or a data source connected to an I/O operation. For example, the resultset-seq function accepts a java.sql.ResultSet JDBC instance ...

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