Input and output

printf

call v%printf([unit=] [, prefix=] [, sep=] [, suffix=] [, iostat=] [, iomsg=])

Argument	Type	Default	Meaning
unit	integer(I4P), in	standard output	an open unit
prefix	character(*), in	''	written before the components
sep	character(*), in	', '	written between the components
suffix	character(*), in	''	written after the components
iostat	integer(I4P), out		the I/O status
iomsg	character(*), out		the I/O message

One line: prefix, x, sep, y, sep, z, suffix. Each component is written with a sign and the shortest digits that read back as the same value (+0.1, -2.0, +0.3333333333333333, +1.0E-7), by PENF's str. For a fixed layout, print the components with a format of your own.

save_into_file and load_from_file

call v%save_into_file(unit= [, fmt=] [, pos=] [, iostat=] [, iomsg=])
call v%load_from_file(unit= [, fmt=] [, pos=] [, iostat=] [, iomsg=])

Argument	Type	Meaning
unit	integer(I4P), in	an open unit, required
fmt	character(*), in	a format for three reals, e.g. '(3F10.4)', for a formatted unit
pos	integer(I8P), in	the position, in file storage units, on a unit opened with access='stream'
iostat	integer(I4P), out	the I/O status: 0, negative at the end of the file, positive on an error
iomsg	character(*), out	the I/O message

Each call writes or reads one record of three values, x, y, z, on a unit opened by you:

• unformatted (no fmt): the exact bits; a double precision vector takes 24 bytes.
• formatted (fmt given): text, with the digits of the format only. fmt is passed to the write/read statement as a character format: '*' is not list-directed I/O and is rejected; list-directed I/O is read(u, *) v%x, v%y, v%z.
• stream (pos given): at that position, on a unit opened with access='stream'; vector n of a file of vectors starts at (n - 1) * v%iolen() + 1.

There is no rec=: on a direct access unit, write and read the components (write(u, rec=i) v%x, v%y, v%z).

iolen

v%iolen(), or iolen(v), is the length of the three components in file storage units, as inquire(iolength=n) v%x, v%y, v%z: the recl of a direct access file of vectors, the stride of a stream file. With gfortran a storage unit is a byte: 12 for vector_R4P, 24 for vector_R8P.

Errors

Always pass iostat

The three procedures never stop the program on an I/O error, unlike a plain read or write: without iostat a failed read or write is silently ignored, and on a read the vector keeps the value it had. Pass iostat, and check it.

call v%load_from_file(unit=u, iostat=ios, iomsg=msg)
if (ios /= 0) error stop 'cannot read the vector: '//trim(msg)

iolen is not pure, and neither are the three procedures: they cannot be called from a pure procedure, nor are they elemental.