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# 63. numericalio

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## 63.1 Introduction to numericalio

`numericalio` is a collection of functions to read and write data files and streams.

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.

separator_flag tells which character separates elements. It is an optional argument for all read and write functions.

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### 63.1.1 Separator flag values for input

For 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 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`.

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### 63.1.2 Separator flag values for output

For 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 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`.

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## 63.2 Functions and Variables for numericalio

Function: read_matrix (file_name)
Function: read_matrix (file_name, separator_flag)
Function: read_matrix (S)
Function: read_matrix (S, separator_flag)

  Reads the file file_name or file stream S and returns its entire content as a matrix. If separator_flag is not specified, the file is assumed space-delimited.

  `read_matrix` infers the size of the matrix from the input data. Each line of the file becomes one row of the matrix. If some lines have different lengths, `read_matrix` complains.

Function: read_lisp_array (file_name, A)
Function: read_lisp_array (file_name, A, separator_flag)
Function: read_lisp_array (S, A)
Function: read_lisp_array (S, A, separator_flag)

  Reads the file file_name or file stream S and returns its entire content as a Lisp array. If separator_flag is not specified, the file is assumed space-delimited.

  `read_lisp_array` requires that the array be declared by `make_array` before calling the read function. (This obviates the need to infer the array dimensions, which could be a problem for arrays with multiple dimensions.)

  `read_lisp_array` does not check to see that the input file conforms in some way to the array dimensions; the input is read as a flat list, then the array is filled using `fillarray`.

Function: read_maxima_array (file_name, A)
Function: read_maxima_array (file_name, A, separator_flag)
Function: read_maxima_array (S, A)
Function: read_maxima_array (S, A, separator_flag)

  Reads the file file_name or file stream S and returns its entire content as a Maxima array. If separator_flag is not specified, the file is assumed space-delimited.

  `read_maxima_array` requires that the array be declared by `array` before calling the read function. (This obviates the need to infer the array dimensions, which could be a hassle for arrays with multiple dimensions.)

  `read_maxima_array` does not check to see that the input file conforms in some way to the array dimensions; the input is read as a flat list, then the array is filled using `fillarray`.

Function: read_hashed_array (file_name, A)
Function: read_hashed_array (file_name, A, separator_flag)
Function: read_hashed_array (S, A)
Function: read_hashed_array (S, A, separator_flag)

  Reads the file file_name or file stream S and returns its entire content as a hashed array. If separator_flag is not specified, the file is assumed space-delimited.

  `read_hashed_array` treats the first item on a line as a hash key, and associates the remainder of the line (as a list) with the key. For example, the line `567 12 17 32 55` is equivalent to `A[567]: [12, 17, 32, 55]$`. Lines need not have the same numbers of elements.

Function: read_nested_list (file_name)
Function: read_nested_list (file_name, separator_flag)
Function: read_nested_list (S)
Function: read_nested_list (S, separator_flag)

  Reads the file file_name or file stream S and returns its entire content as a nested list. If separator_flag is not specified, the file is assumed space-delimited.

  `read_nested_list` returns a list which has a sublist for each line of input. Lines need not have the same numbers of elements. Empty lines are not ignored: an empty line yields an empty sublist.

Function: read_list (file_name)
Function: read_list (file_name, separator_flag)
Function: read_list (S)
Function: read_list (S, separator_flag)

  Reads the file file_name or file stream S and returns its entire content as a flat list. If separator_flag is not specified, the file is assumed space-delimited.

Function: write_data (X, file_name)
Function: write_data (object, file_name, separator_flag)
Function: write_data (X, S)
Function: write_data (object, S, separator_flag)

  `write_data` writes the object X to the file file_name or file stream S.

  `write_data` writes matrices in row-major form, with one line per row.

  `write_data` writes Lisp and Maxima declared arrays in row-major form, with a new line at the end of every slab. Higher-dimensional slabs are separated by additional new lines.

  `write_data` writes hashed arrays with a key followed by the associated list on each line.

  `write_data` writes a nested list with each sublist on one line.

  `write_data` writes a flat list all on one line.

  When `write_data` writes to a file, the global variable `file_output_append` governs whether the output file is appended or truncated.

  No special action concerning appending or truncating is taken when `write_data` writes to a file stream. The file stream is not closed by `write_data`.

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