This function works with files being used on the READ statement.
Given a file handle or file name file, returns an integer scalar
1 if the last line in the file has been read or 0 if more lines are
available. Determining this requires attempting to read another line,
which means that REREAD on the next READ command
following EOF on the same file will be ineffective.
The EOF function gives a matrix program the flexibility to read
a file with text data without knowing the length of the file in
advance. For example, the following program will read all the lines
of data in data.txt, each consisting of three numbers, as rows
in matrix data:
MATRIX.
COMPUTE data={}.
LOOP IF NOT EOF('data.txt').
READ row/FILE='data.txt'/FIELD=1 TO 1000/SIZE={1,3}.
COMPUTE data={data; row}.
END LOOP.
PRINT data.
END MATRIX.