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# Component files

A component file (jfile) can be thought of as a boxed list stored in a file. An item of the boxed list on file is referred to as a component. The script jfiles.ijs provides the utilities for working with jfiles.

       load 'jfiles'
       f =. 'user\data.jf'
       jcreate f
    1

       'first component' jappend f
    0

       (1.5+i.2 3) jappend f
    1

       ('asdf';23) jappend f
    2 3

       (<'mum';'dad') jappend f
    4

The `jsize` result gives file information, including the indexes of the first and last items.

       jsize f
    0 5 1408 0

       jread f;0
    +---------------+
    ¦first component¦
    +---------------+

       jread f;1
    +-----------+
    ¦1.5 2.5 3.5¦
    ¦4.5 5.5 6.5¦
    +-----------+

       jread f;2
    +----+
    ¦asdf¦
    +----+

       jread f;3
    +--+
    ¦23¦
    +--+

       jread f;4
    +---------+
    ¦+-------+¦
    ¦¦mum¦dad¦¦
    ¦+-------+¦
    +---------+

       'new' jreplace f;3
    3

       jread f;i.5
    +----------------------------------------------+
    ¦first component¦1.5 2.5 3.5¦asdf¦new¦+-------+¦
    ¦               ¦4.5 5.5 6.5¦    ¦   ¦¦mum¦dad¦¦
    ¦               ¦           ¦    ¦   ¦+-------+¦
    +----------------------------------------------+

Jfiles are documented in the J Online Documentation.

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