(maxima.info)Introduction to numericalio

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Enter node , (file) or (file)node

74.1 Introduction to numericalio
================================

'numericalio' is a collection of functions to read and write files and
streams.  Functions for plain-text input and output can read and write
numbers (integer, float, or bigfloat), symbols, and strings.  Functions
for binary input and output can read and write only floating-point
numbers.

   If there already exists a list, matrix, or array object to store
input data, 'numericalio' input functions can write data into that
object.  Otherwise, 'numericalio' can guess, to some degree, the
structure of an object to store the data, and return that object.

74.1.1 Plain-text input and output
----------------------------------

In plain-text input and output, it is assumed that each item to read or
write is an atom: an integer, float, bigfloat, string, or symbol, and
not a rational or complex number or any other kind of nonatomic
expression.  The 'numericalio' functions may attempt to do something
sensible faced with nonatomic expressions, but the results are not
specified here and subject to change.

   Atoms in both input and output files have the same format as in
Maxima batch files or the interactive console.  In particular, strings
are enclosed in double quotes, backslash '\' prevents any special
interpretation of the next character, and the question mark '?' is
recognized at the beginning of a symbol to mean a Lisp symbol (as
opposed to a Maxima symbol).  No continuation character (to join broken
lines) is recognized.

74.1.2 Separator flag values for input
--------------------------------------

The functions for plain-text input and output take an optional argument,
<separator_flag>, that tells what character separates data.

   For plain-text input, these values of <separator_flag> are
recognized: 'comma' for comma separated values, 'pipe' for values
separated by the vertical bar character '|', 'semicolon' for values
separated by semicolon ';', and 'space' for values separated by space or
tab characters.  If the file name ends in '.csv' and <separator_flag> is
not specified, 'comma' is assumed.  If the file name ends in something
other than '.csv' and 'separator_flag' is not specified, 'space' is
assumed.

   In plain-text input, multiple successive space and tab characters
count as a single separator.  However, multiple comma, pipe, or
semicolon characters are significant.  Successive comma, pipe, or
semicolon characters (with or without intervening spaces or tabs) are
considered to have 'false' between the separators.  For example,
'1234,,Foo' is treated the same as '1234,false,Foo'.

74.1.3 Separator flag values for output
---------------------------------------

For plain-text output, 'tab', for values separated by the tab character,
is recognized as a value of <separator_flag>, as well as 'comma',
'pipe', 'semicolon', and 'space'.

   In plain-text output, 'false' atoms are written as such; a list
'[1234, false, Foo]' is written '1234,false,Foo', and there is no
attempt to collapse the output to '1234,,Foo'.

74.1.4 Binary floating-point input and output
---------------------------------------------

'numericalio' functions can read and write 8-byte IEEE 754
floating-point numbers.  These numbers can be stored either least
significant byte first or most significant byte first, according to the
global flag set by 'assume_external_byte_order'.  If not specified,
'numericalio' assumes the external byte order is most-significant byte
first.

   Other kinds of numbers are coerced to 8-byte floats; 'numericalio'
cannot read or write binary non-numeric data.

   Some Lisp implementations do not recognize IEEE 754 special values
(positive and negative infinity, not-a-number values, denormalized
values).  The effect of reading such values with 'numericalio' is
undefined.

   'numericalio' includes functions to open a stream for reading or
writing a stream of bytes.