TEXT_IO

To work with text files, an Ada program must import the TEXT_IO package.

TEXT_IO provides:

• procedures for reading and writing characters and strings
  • GET, PUT, GET_LINE, PUT_LINE
• generic packages for I/O of integers, floats, enumeration types
  • since characters typed by a user need to be converted to the appropriate numeric or enumeration value
• procedures and functions to detect or impose the page/line/character structure
  • described below

Page - line - character

Procedures to create the page/line/character structure:

• go to a given character position:
  • SET_COL - go to nominated column in output file (on next line, if already past that position on this line)
• go to a given line:
  • NEW_LINE - go to next line of output
  • SET_LINE - go to nominated line in output file
• go to next page:
  • NEW_PAGE - go to next page of output

Procedures to recognise the page/line/character structure:

• SKIP_LINE - go to start of next line of input
• SKIP_PAGE - go to start of next page of input

Functions to recognise position within the page/line/character structure:

• PAGE - what page number are we up to in the file?
• LINE - what line number are we up to on the page?
• COL - what character position are we up to on the line?

Example:

        SET_LINE (2);
        SET_COL (30); PUT ("Student Results Report");

        SET_LINE (4);
        SET_COL ( 5); PUT ("Student name");
        SET_COL (35); PUT ("Assignments");
        SET_COL (50); PUT ("Exams");
        SET_COL (65); PUT ("Average");

        SET_LINE (6);

Line Length

For output files, you can define automatic line and page lengths

• SET_LINE_LENGTH for lines
• SET_PAGE_LENGTH for pages

SET_LINE_LENGTH:

• EOL generated automatically when limit reached
• default is 0 (unconstrained)

Example:

    SET_LINE_LENGTH (30);
    for i in 1 .. 20 loop
        PUT (i**2, width => 5);
    end loop;



    '    1    4    9   16   25   36'
    '   49   64   81  100  121  144'
    '  169  196  225  256  289  324'
    '  361  400'

SET_PAGE_LENGTH is analogous