Topic: APLX Help : Help on APL language : System Functions & Variables : ⎕FDROP Drop components from start or end of file
[ Previous | Next | Contents | Index | APL Home ]

www.microapl.co.uk

⎕FDROP Drop components from start or end of file


The ⎕FDROP function deletes one or more components from the start or end of the file, without renumbering the remaining components. The syntax is:

      ⎕FDROP TIENO N {PASS}

TIENO is the tie number you used to tie or create the file (or the tie number returned by APLX if you tied or created it using 0 instead of your own tie number). If you tied the file using a pass number, you must provide the same pass number, as the PASS parameter.

The parameter N is a positive or negative integer. If it is positive, the first N components of the file are deleted. If it is negative, the last -N components are deleted. In both cases, existing components are not re-numbered.

For example, suppose you have a file with components numbered from 1 to 12. After executing the two statements:

      ⎕FDROP TIENO,2
      ⎕FDROP TIENO, ¯3

the first component in the file will be component 3, and the last will be component 9. The original components 1, 2, 10, 11, 12 will no longer exist. The original components 3 through 9 still exist, and retain the same component numbers.

See also the function ⎕FDELETE which deletes a single component anywhere in the file, re-numbering the remaining components accordingly.


Topic: APLX Help : Help on APL language : System Functions & Variables : ⎕FDROP Drop components from start or end of file
[ Previous | Next | Contents | Index | APL Home ]