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# 13. File Input and Output

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## 13.1 Comments

A comment in Maxima input is any text between `/*` and `*/`.

The Maxima parser treats a comment as whitespace for the purpose of finding tokens in the input stream; a token always ends at a comment. An input such as `a/* foo */b` contains two tokens, `a` and `b`, and not a single token `ab`. Comments are otherwise ignored by Maxima; neither the content nor the location of comments is stored in parsed input expressions.

Comments can be nested to arbitrary depth. The `/*` and `*/` delimiters form matching pairs. There must be the same number of `/*` as there are `*/`.

Examples:

    (%i1) /* aa is a variable of interest */  aa : 1234;
    (%o1)                         1234
    (%i2) /* Value of bb depends on aa */  bb : aa^2;
    (%o2)                        1522756
    (%i3) /* User-defined infix operator */  infix ("b");
    (%o3)                           b
    (%i4) /* Parses same as a b c, not abc */  a/* foo */b/* bar */c;
    (%o4)                         a b c
    (%i5) /* Comments /* can be nested /* to any depth */ */ */  1 + xyz;
    (%o5)                        xyz + 1

·

@ref{Category: Syntax}

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## 13.2 Files

A file is simply an area on a particular storage device which contains data or text. Files on the disks are figuratively grouped into "directories". A directory is just a list of files. Commands which deal with files are:

       appendfile           batch                 batchload
       closefile            file_output_append    filename_merge
       file_search          file_search_maxima    file_search_lisp
       file_search_demo     file_search_usage     file_search_tests
       file_type            file_type_lisp        file_type_maxima
       load                 load_pathname         loadfile
       loadprint            pathname_directory    pathname_name
       pathname_type        printfile             save
       stringout            with_stdout           writefile

When a file name is passed to functions like `plot2d`, `save`, or `writefile` and the file name does not include a path, Maxima stores the file in the current working directory. The current working directory depends on the system like Windows or Linux and on the installation.

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## 13.3 Functions and Variables for File Input and Output

Function: appendfile (filename)

  Appends a console transcript to filename. `appendfile` is the same as `writefile`, except that the transcript file, if it exists, is always appended.

  `closefile` closes the transcript file opened by `appendfile` or `writefile`.

  ·

  @ref{Category: File output} · @ref{Category: Console interaction}

Function: batch (filename)
Function: batch (filename, `option`)

  `batch(filename)` reads Maxima expressions from filename and evaluates them. `batch` searches for filename in the list `file_search_maxima`. See also `file_search`.

  `batch(filename, `demo`)` is like `demo(filename)`. In this case `batch` searches for filename in the list `file_search_demo`. See `demo`.

  `batch(filename, `test`)` is like `run_testsuite` with the option `display_all=true`. For this case `batch` searches filename in the list `file_search_maxima` and not in the list `file_search_tests` like `run_testsuite`. Furthermore, `run_testsuite` runs tests which are in the list `testsuite_files`. With `batch` it is possible to run any file in a test mode, which can be found in the list `file_search_maxima`. This is useful, when writing a test file.

  filename comprises a sequence of Maxima expressions, each terminated with `;` or `$`. The special variable `%` and the function `%th` refer to previous results within the file. The file may include `:lisp` constructs. Spaces, tabs, and newlines in the file are ignored. A suitable input file may be created by a text editor or by the `stringout` function.

  `batch` reads each input expression from filename, displays the input to the console, computes the corresponding output expression, and displays the output expression. Input labels are assigned to the input expressions and output labels are assigned to the output expressions. `batch` evaluates every input expression in the file unless there is an error. If user input is requested (by `asksign` or `askinteger`, for example) `batch` pauses to collect the requisite input and then continue.

  It may be possible to halt `batch` by typing `control-C` at the console. The effect of `control-C` depends on the underlying Lisp implementation.

  `batch` has several uses, such as to provide a reservoir for working command lines, to give error-free demonstrations, or to help organize one's thinking in solving complex problems.

  `batch` evaluates its argument. `batch` returns the path of filename as a string, when called with no second argument or with the option `demo`. When called with the option `test`, the return value is a an empty list `[]` or a list with filename and the numbers of the tests which have failed.

  See also `load`, `batchload`, and `demo`.

  ·

  @ref{Category: Session management} · @ref{Category: File input}

Function: batchload (filename)

  Reads Maxima expressions from filename and evaluates them, without displaying the input or output expressions and without assigning labels to output expressions. Printed output (such as produced by `print` or `describe`) is displayed, however.

  The special variable `%` and the function `%th` refer to previous results from the interactive interpreter, not results within the file. The file cannot include `:lisp` constructs.

  `batchload` returns the path of filename, as a string. `batchload` evaluates its argument.

  See also `batch`, and `load`.

  ·

  @ref{Category: Session management} · @ref{Category: File input}

Function: closefile ()

  Closes the transcript file opened by `writefile` or `appendfile`.

  ·

  @ref{Category: File output} · @ref{Category: Console interaction}

Option variable: file_output_append

  Default value: `false`

  `file_output_append` governs whether file output functions append or truncate their output file. When `file_output_append` is `true`, such functions append to their output file. Otherwise, the output file is truncated.

  `save`, `stringout`, and `with_stdout` respect `file_output_append`. Other functions which write output files do not respect `file_output_append`. In particular, plotting and translation functions always truncate their output file, and `tex` and `appendfile` always append.

  ·

  @ref{Category: File output} · @ref{Category: Global flags}

Function: filename_merge (path, filename)

  Constructs a modified path from path and filename. If the final component of path is of the form `###.something`, the component is replaced with `filename.something`. Otherwise, the final component is simply replaced by filename.

  The result is a Lisp pathname object.

  ·

  @ref{Category: File input} · @ref{Category: File output}

Function: file_search (filename)
Function: file_search (filename, pathlist)

  `file_search` searches for the file filename and returns the path to the file (as a string) if it can be found; otherwise `file_search` returns `false`. `file_search (filename)` searches in the default search directories, which are specified by the `file_search_maxima`, `file_search_lisp`, and `file_search_demo` variables.

  `file_search` first checks if the actual name passed exists, before attempting to match it to "wildcard" file search patterns. See `file_search_maxima` concerning file search patterns.

  The argument filename can be a path and file name, or just a file name, or, if a file search directory includes a file search pattern, just the base of the file name (without an extension). For example,

      file_search ("/home/wfs/special/zeta.mac");
      file_search ("zeta.mac");
      file_search ("zeta");

  all find the same file, assuming the file exists and `/home/wfs/special/###.mac` is in `file_search_maxima`.

  `file_search (filename, pathlist)` searches only in the directories specified by pathlist, which is a list of strings. The argument pathlist supersedes the default search directories, so if the path list is given, `file_search` searches only the ones specified, and not any of the default search directories. Even if there is only one directory in pathlist, it must still be given as a one-element list.

  The user may modify the default search directories. See `file_search_maxima`.

  `file_search` is invoked by `load` with `file_search_maxima` and `file_search_lisp` as the search directories.

  ·

  @ref{Category: File input}

Option variable: file_search_maxima
Option variable: file_search_lisp
Option variable: file_search_demo
Option variable: file_search_usage
Option variable: file_search_tests

  These variables specify lists of directories to be searched by `load`, `demo`, and some other Maxima functions. The default values of these variables name various directories in the Maxima installation.

  The user can modify these variables, either to replace the default values or to append additional directories. For example,

      file_search_maxima: ["/usr/local/foo/###.mac",
          "/usr/local/bar/###.mac"]$

  replaces the default value of `file_search_maxima`, while

      file_search_maxima: append (file_search_maxima,
          ["/usr/local/foo/###.mac", "/usr/local/bar/###.mac"])$

  appends two additional directories. It may be convenient to put such an expression in the file `maxima-init.mac` so that the file search path is assigned automatically when Maxima starts. See also Introduction for Runtime Environment.

  Multiple filename extensions and multiple paths can be specified by special "wildcard" constructions. The string `###` expands into the sought-after name, while a comma-separated list enclosed in curly braces `{foo,bar,baz}` expands into multiple strings. For example, supposing the sought-after name is `neumann`,

      "/home/{wfs,gcj}/###.{lisp,mac}"

  expands into `/home/wfs/neumann.lisp`, `/home/gcj/neumann.lisp`, `/home/wfs/neumann.mac`, and `/home/gcj/neumann.mac`.

  ·

  @ref{Category: File input} · @ref{Category: Global variables}

Function: file_type (filename)

  Returns a guess about the content of filename, based on the filename extension. filename need not refer to an actual file; no attempt is made to open the file and inspect the content.

  The return value is a symbol, either `object`, `lisp`, or `maxima`. If the extension is matches one of the values in `file_type_maxima`, `file_type` returns `maxima`. If the extension matches one of the values in `file_type_lisp`, `file_type` returns `lisp`. If none of the above, `file_type` returns `object`.

  See also `pathname_type`.

  See `file_type_maxima` and `file_type_lisp` for the default values.

  Examples:

      (%i2) map('file_type,
                ["test.lisp", "test.mac", "test.dem", "test.txt"]);
      (%o2)            [lisp, maxima, maxima, object]

  ·

  @ref{Category: File input}

Option variable: file_type_lisp

  Default value: `[l, lsp, lisp]`

  `file_type_lisp` is a list of file extensions that maxima recognizes as denoting a Lisp source file.

  See also `file_type`.

Option variable: file_type_maxima

  Default value: `[mac, mc, demo, dem, dm1, dm2, dm3, dmt]`

  `file_type_maxima` is a list of file extensions that maxima recognizes as denoting a Maxima source file.

  See also `file_type`.

Function: load (filename)

  Evaluates expressions in filename, thus bringing variables, functions, and other objects into Maxima. The binding of any existing object is clobbered by the binding recovered from filename. To find the file, `load` calls `file_search` with `file_search_maxima` and `file_search_lisp` as the search directories. If `load` succeeds, it returns the name of the file. Otherwise `load` prints an error message.

  `load` works equally well for Lisp code and Maxima code. Files created by `save`, `translate_file`, and `compile_file`, which create Lisp code, and `stringout`, which creates Maxima code, can all be processed by `load`. `load` calls `loadfile` to load Lisp files and `batchload` to load Maxima files.

  `load` does not recognize `:lisp` constructs in Maxima files, and while processing filename, the global variables `_`, `__`, `%`, and `%th` have whatever bindings they had when `load` was called.

  See also `loadfile`, `batch`, `batchload`, and `demo`. `loadfile` processes Lisp files; `batch`, `batchload`, and `demo` process Maxima files.

  See `file_search` for more detail about the file search mechanism.

  `load` evaluates its argument.

  ·

  @ref{Category: Session management} · @ref{Category: File input}

System variable: load_pathname

  Default value: `false`

  When a file is loaded with the functions `load`, `loadfile` or `batchload` the system variable `load_pathname` is bound to the pathname of the file which is processed.

  The variable `load_pathname` can be accessed from the file during the loading.

  Example:

  Suppose we have a batchfile `test.mac` in the directory

  `"/home/dieter/workspace/mymaxima/temp/"` with the following commands

      print("The value of load_pathname is: ", load_pathname)$
      print("End of batchfile")$

  then we get the following output

      (%i1) load("/home/dieter/workspace/mymaxima/temp/test.mac")$
      The value of load_pathname is:
                         /home/dieter/workspace/mymaxima/temp/test.mac
      End of batchfile

  ·

  @ref{Category: File input}

Function: loadfile (filename)

  Evaluates Lisp expressions in filename. `loadfile` does not invoke `file_search`, so `filename` must include the file extension and as much of the path as needed to find the file.

  `loadfile` can process files created by `save`, `translate_file`, and `compile_file`. The user may find it more convenient to use `load` instead of `loadfile`.

  ·

  @ref{Category: Session management} · @ref{Category: File input}

Option variable: loadprint

  Default value: `true`

  `loadprint` tells whether to print a message when a file is loaded.

  - When `loadprint` is `true`, always print a message.
  - When `loadprint` is `'loadfile`, print a message only if a file is loaded by the function `loadfile`.
  - When `loadprint` is `'autoload`, print a message only if a file is automatically loaded. See `setup_autoload`.
  - When `loadprint` is `false`, never print a message.
  ·

  @ref{Category: File input} · @ref{Category: Global flags}

Function: pathname_directory (pathname)
Function: pathname_name (pathname)
Function: pathname_type (pathname)

  These functions return the components of pathname.

  Examples:

      (%i1) pathname_directory("/home/dieter/maxima/changelog.txt");
      (%o1)                 /home/dieter/maxima/
      (%i2) pathname_name("/home/dieter/maxima/changelog.txt");
      (%o2)                       changelog
      (%i3) pathname_type("/home/dieter/maxima/changelog.txt");
      (%o3)                          txt

  ·

  @ref{Category: File input}

Function: printfile (path)

  Prints the file named by path to the console. path may be a string or a symbol; if it is a symbol, it is converted to a string.

  If path names a file which is accessible from the current working directory, that file is printed to the console. Otherwise, `printfile` attempts to locate the file by appending path to each of the elements of `file_search_usage` via `filename_merge`.

  `printfile` returns path if it names an existing file, or otherwise the result of a successful filename merge.

  ·

  @ref{Category: File input} · @ref{Category: Console interaction}

Function: save (filename, name_1, name_2, name_3, …)
Function: save (filename, values, functions, labels, …)
Function: save (filename, [m, n])
Function: save (filename, name_1=expr_1, …)
Function: save (filename, all)
Function: save (filename, name_1=expr_1, name_2=expr_2, …)

  Stores the current values of name_1, name_2, name_3, …, in filename. The arguments are the names of variables, functions, or other objects. If a name has no value or function associated with it, it is ignored. `save` returns filename.

  `save` stores data in the form of Lisp expressions. The data stored by `save` may be recovered by `load (filename)`. See `load`.

  The global flag `file_output_append` governs whether `save` appends or truncates the output file. When `file_output_append` is `true`, `save` appends to the output file. Otherwise, `save` truncates the output file. In either case, `save` creates the file if it does not yet exist.

  The special form `save (filename, values, functions, labels, ...)` stores the items named by `values`, `functions`, `labels`, etc. The names may be any specified by the variable `infolists`. `values` comprises all user-defined variables.

  The special form `save (filename, [m, n])` stores the values of input and output labels m through n. Note that m and n must be literal integers. Input and output labels may also be stored one by one, e.g., `save ("foo.1", %i42, %o42)`. `save (filename, labels)` stores all input and output labels. When the stored labels are recovered, they clobber existing labels.

  The special form `save (filename, name_1=expr_1, name_2=expr_2, ...)` stores the values of expr_1, expr_2, …, with names name_1, name_2, … It is useful to apply this form to input and output labels, e.g., `save ("foo.1", aa=%o88)`. The right-hand side of the equality in this form may be any expression, which is evaluated. This form does not introduce the new names into the current Maxima environment, but only stores them in filename.

  These special forms and the general form of `save` may be mixed at will. For example, `save (filename, aa, bb, cc=42, functions, [11, 17])`.

  The special form `save (filename, all)` stores the current state of Maxima. This includes all user-defined variables, functions, arrays, etc., as well as some automatically defined items. The saved items include system variables, such as `file_search_maxima` or `showtime`, if they have been assigned new values by the user; see `myoptions`.

  `save` evaluates filename and quotes all other arguments.

  ·

  @ref{Category: Session management} · @ref{Category: File output}

Function: stringout (filename, expr_1, expr_2, expr_3, …)
Function: stringout (filename, [m, n])
Function: stringout (filename, input)
Function: stringout (filename, functions)
Function: stringout (filename, values)

  `stringout` writes expressions to a file in the same form the expressions would be typed for input. The file can then be used as input for the `batch` or `demo` commands, and it may be edited for any purpose. `stringout` can be executed while `writefile` is in progress.

  The global flag `file_output_append` governs whether `stringout` appends or truncates the output file. When `file_output_append` is `true`, `stringout` appends to the output file. Otherwise, `stringout` truncates the output file. In either case, `stringout` creates the file if it does not yet exist.

  The general form of `stringout` writes the values of one or more expressions to the output file. Note that if an expression is a variable, only the value of the variable is written and not the name of the variable. As a useful special case, the expressions may be input labels (`%i1`, `%i2`, `%i3`, …) or output labels (`%o1`, `%o2`, `%o3`, …).

  If `grind` is `true`, `stringout` formats the output using the `grind` format. Otherwise the `string` format is used. See `grind` and `string`.

  The special form `stringout (filename, [m, n])` writes the values of input labels m through n, inclusive.

  The special form `stringout (filename, input)` writes all input labels to the file.

  The special form `stringout (filename, functions)` writes all user-defined functions (named by the global list `functions`) to the file.

  The special form `stringout (filename, values)` writes all user-assigned variables (named by the global list `values`) to the file. Each variable is printed as an assignment statement, with the name of the variable, a colon, and its value. Note that the general form of `stringout` does not print variables as assignment statements.

  ·

  @ref{Category: Session management} · @ref{Category: File output}

Function: with_stdout (f, expr_1, expr_2, expr_3, …)
Function: with_stdout (s, expr_1, expr_2, expr_3, …)

  Evaluates expr_1, expr_2, expr_3, … and writes any output thus generated to a file f or output stream s. The evaluated expressions are not written to the output. Output may be generated by `print`, `display`, `grind`, among other functions.

  The global flag `file_output_append` governs whether `with_stdout` appends or truncates the output file f. When `file_output_append` is `true`, `with_stdout` appends to the output file. Otherwise, `with_stdout` truncates the output file. In either case, `with_stdout` creates the file if it does not yet exist.

  `with_stdout` returns the value of its final argument.

  See also `writefile`.

      (%i1) with_stdout ("tmp.out", for i:5 thru 10 do
            print (i, "! yields", i!))$
      (%i2) printfile ("tmp.out")$
      5 ! yields 120
      6 ! yields 720
      7 ! yields 5040
      8 ! yields 40320
      9 ! yields 362880
      10 ! yields 3628800

  ·

  @ref{Category: File output}

Function: writefile (filename)

  Begins writing a transcript of the Maxima session to filename. All interaction between the user and Maxima is then recorded in this file, just as it appears on the console.

  As the transcript is printed in the console output format, it cannot be reloaded into Maxima. To make a file containing expressions which can be reloaded, see `save` and `stringout`. `save` stores expressions in Lisp form, while `stringout` stores expressions in Maxima form.

  The effect of executing `writefile` when filename already exists depends on the underlying Lisp implementation; the transcript file may be clobbered, or the file may be appended. `appendfile` always appends to the transcript file.

  It may be convenient to execute `playback` after `writefile` to save the display of previous interactions. As `playback` displays only the input and output variables (`%i1`, `%o1`, etc.), any output generated by a print statement in a function (as opposed to a return value) is not displayed by `playback`.

  `closefile` closes the transcript file opened by `writefile` or `appendfile`.

  ·

  @ref{Category: File output} · @ref{Category: Console interaction}

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## 13.4 Functions and Variables for TeX Output

Function: tex (expr)
Function: tex (expr, destination)
Function: tex (expr, false)
Function: tex (label)
Function: tex (label, destination)
Function: tex (label, false)

  Prints a representation of an expression suitable for the TeX document preparation system. The result is a fragment of a document, which can be copied into a larger document but not processed by itself.

  `tex (expr)` prints a TeX representation of expr on the console.

  `tex (label)` prints a TeX representation of the expression named by label and assigns it an equation label (to be displayed to the left of the expression). The TeX equation label is the same as the Maxima label.

  destination may be an output stream or file name. When destination is a file name, `tex` appends its output to the file. The functions `openw` and `opena` create output streams.

  `tex (expr, false)` and `tex (label, false)` return their TeX output as a string.

  `tex` evaluates its first argument after testing it to see if it is a label. Quote-quote `''` forces evaluation of the argument, thereby defeating the test and preventing the label.

  See also `texput`.

  Examples:

      (%i1) integrate (1/(1+x^3), x);
                                          2 x - 1
                        2            atan(-------)
                   log(x  - x + 1)        sqrt(3)    log(x + 1)
      (%o1)      - --------------- + ------------- + ----------
                          6             sqrt(3)          3
      (%i2) tex (%o1);
      $$-{{\log \left(x^2-x+1\right)}\over{6}}+{{\arctan \left({{2\,x-1
       }\over{\sqrt{3}}}\right)}\over{\sqrt{3}}}+{{\log \left(x+1\right)
       }\over{3}}\leqno{\tt (\%o1)}$$
      (%o2)                          (\%o1)
      (%i3) tex (integrate (sin(x), x));
      $$-\cos x$$
      (%o3)                           false
      (%i4) tex (%o1, "foo.tex");
      (%o4)                          (\%o1)

  `tex (expr, false)` returns its TeX output as a string.

      (%i1) S : tex (x * y * z, false);
      (%o1) $$x\,y\,z$$
      (%i2) S;
      (%o2) $$x\,y\,z$$

  ·

  @ref{Category: TeX output} · @ref{Category: File output}

Function: tex1 (e)

  Returns a string which represents the TeX output for the expressions e. The TeX output is not enclosed in delimiters for an equation or any other environment.

  Examples:

      (%i1) tex1 (sin(x) + cos(x));
      (%o1)                     \sin x+\cos x

Function: texput (a, s)
Function: texput (a, f)
Function: texput (a, s, operator_type)
Function: texput (a, [s_1, s_2], matchfix)
Function: texput (a, [s_1, s_2, s_3], matchfix)

  Assign the TeX output for the atom a, which can be a symbol or the name of an operator.

  `texput (a, s)` causes the `tex` function to interpolate the string s into the TeX output in place of a.

  `texput (a, f)` causes the `tex` function to call the function f to generate TeX output. f must accept one argument, which is an expression which has operator a, and must return a string (the TeX output). f may call `tex1` to generate TeX output for the arguments of the input expression.

  `texput (a, s, operator_type)`, where operator_type is `prefix`, `infix`, `postfix`, `nary`, or `nofix`, causes the `tex` function to interpolate s into the TeX output in place of a, and to place the interpolated text in the appropriate position.

  `texput (a, [s_1, s_2], matchfix)` causes the `tex` function to interpolate s_1 and s_2 into the TeX output on either side of the arguments of a. The arguments (if more than one) are separated by commas.

  `texput (a, [s_1, s_2, s_3], matchfix)` causes the `tex` function to interpolate s_1 and s_2 into the TeX output on either side of the arguments of a, with s_3 separating the arguments.

  Examples:

  Assign TeX output for a variable.

      (%i1) texput (me,"\\mu_e");
      (%o1)                         \mu_e
      (%i2) tex (me);
      $$\mu_e$$
      (%o2)                         false

  Assign TeX output for an ordinary function (not an operator).

      (%i1) texput (lcm, "\\mathrm{lcm}");
      (%o1)                     \mathrm{lcm}
      (%i2) tex (lcm (a, b));
      $$\mathrm{lcm}\left(a , b\right)$$
      (%o2)                         false

  Call a function to generate TeX output.

      (%i1) texfoo (e) := block ([a, b], [a, b] : args (e),
        concat("\\left[\\stackrel{",tex1(b),"}{",tex1(a),"}\\right]"))$
      (%i2) texput (foo, texfoo);
      (%o2)                        texfoo
      (%i3) tex (foo (2^x, %pi));
      $$\left[\stackrel{\pi}{2^{x}}\right]$$
      (%o3)                         false

  Assign TeX output for a prefix operator.

      (%i1) prefix ("grad");
      (%o1)                         grad
      (%i2) texput ("grad", " \\nabla ", prefix);
      (%o2)                        \nabla
      (%i3) tex (grad f);
      $$ \nabla f$$
      (%o3)                         false

  Assign TeX output for an infix operator.

      (%i1) infix ("~");
      (%o1)                           ~
      (%i2) texput ("~", " \\times ", infix);
      (%o2)                        \times
      (%i3) tex (a ~ b);
      $$a \times b$$
      (%o3)                         false

  Assign TeX output for a postfix operator.

      (%i1) postfix ("##");
      (%o1)                          ##
      (%i2) texput ("##", "!!", postfix);
      (%o2)                          !!
      (%i3) tex (x ##);
      $$x!!$$
      (%o3)                         false

  Assign TeX output for a nary operator.

      (%i1) nary ("@@");
      (%o1)                          @@
      (%i2) texput ("@@", " \\circ ", nary);
      (%o2)                         \circ
      (%i3) tex (a @@ b @@ c @@ d);
      $$a \circ b \circ c \circ d$$
      (%o3)                         false

  Assign TeX output for a nofix operator.

      (%i1) nofix ("foo");
      (%o1)                          foo
      (%i2) texput ("foo", "\\mathsc{foo}", nofix);
      (%o2)                     \mathsc{foo}
      (%i3) tex (foo);
      $$\mathsc{foo}$$
      (%o3)                         false

  Assign TeX output for a matchfix operator.

      (%i1) matchfix ("<<", ">>");
      (%o1)                          <<
      (%i2) texput ("<<", [" \\langle ", " \\rangle "], matchfix);
      (%o2)                [ \langle ,  \rangle ]
      (%i3) tex (<<a>>);
      $$ \langle a \rangle $$
      (%o3)                         false
      (%i4) tex (<<a, b>>);
      $$ \langle a , b \rangle $$
      (%o4)                         false
      (%i5) texput ("<<", [" \\langle ", " \\rangle ", " \\, | \\,"],
            matchfix);
      (%o5)           [ \langle ,  \rangle ,  \, | \,]
      (%i6) tex (<<a>>);
      $$ \langle a \rangle $$
      (%o6)                         false
      (%i7) tex (<<a, b>>);
      $$ \langle a \, | \,b \rangle $$
      (%o7)                         false

  ·

  @ref{Category: TeX output}

Function: get_tex_environment (op)
Function: set_tex_environment (op, before, after)

  Customize the TeX environment output by `tex`. As maintained by these functions, the TeX environment comprises two strings: one is printed before any other TeX output, and the other is printed after.

  Only the TeX environment of the top-level operator in an expression is output; TeX environments associated with other operators are ignored.

  `get_tex_environment` returns the TeX enviroment which is applied to the operator op; returns the default if no other environment has been assigned.

  `set_tex_environment` assigns the TeX environment for the operator op.

  Examples:

      (%i1) get_tex_environment (":=");
      (%o1) [
      \begin{verbatim}
      , ;
      \end{verbatim}
      ]
      (%i2) tex (f (x) := 1 - x);

      \begin{verbatim}
      f(x):=1-x;
      \end{verbatim}

      (%o2)                         false
      (%i3) set_tex_environment (":=", "$$", "$$");
      (%o3)                       [$$, $$]
      (%i4) tex (f (x) := 1 - x);
      $$f(x):=1-x$$
      (%o4)                         false

  ·

  @ref{Category: TeX output}

Function: get_tex_environment_default ()
Function: set_tex_environment_default (before, after)

  Customize the TeX environment output by `tex`. As maintained by these functions, the TeX environment comprises two strings: one is printed before any other TeX output, and the other is printed after.

  `get_tex_environment_default` returns the TeX environment which is applied to expressions for which the top-level operator has no specific TeX environment (as assigned by `set_tex_environment`).

  `set_tex_environment_default` assigns the default TeX environment.

  Examples:

      (%i1) get_tex_environment_default ();
      (%o1)                       [$$, $$]
      (%i2) tex (f(x) + g(x));
      $$g\left(x\right)+f\left(x\right)$$
      (%o2)                         false
      (%i3) set_tex_environment_default ("\\begin{equation}
      ", "
      \\end{equation}");
      (%o3) [\begin{equation}
      ,
      \end{equation}]
      (%i4) tex (f(x) + g(x));
      \begin{equation}
      g\left(x\right)+f\left(x\right)
      \end{equation}
      (%o4)                         false

  ·

  @ref{Category: TeX output}

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## 13.5 Functions and Variables for Fortran Output

Option variable: fortindent

  Default value: `0`

  `fortindent` controls the left margin indentation of expressions printed out by the `fortran` command. `0` gives normal printout (i.e., 6 spaces), and positive values will causes the expressions to be printed farther to the right.

  ·

  @ref{Category: Translation and compilation}

Function: fortran (expr)

  Prints expr as a Fortran statement. The output line is indented with spaces. If the line is too long, `fortran` prints continuation lines. `fortran` prints the exponentiation operator `^` as `**`, and prints a complex number `a + b %i` in the form `(a,b)`.

  expr may be an equation. If so, `fortran` prints an assignment statement, assigning the right-hand side of the equation to the left-hand side. In particular, if the right-hand side of expr is the name of a matrix, then `fortran` prints an assignment statement for each element of the matrix.

  If expr is not something recognized by `fortran`, the expression is printed in `grind` format without complaint. `fortran` does not know about lists, arrays, or functions.

  `fortindent` controls the left margin of the printed lines. `0` is the normal margin (i.e., indented 6 spaces). Increasing `fortindent` causes expressions to be printed further to the right.

  When `fortspaces` is `true`, `fortran` fills out each printed line with spaces to 80 columns.

  `fortran` evaluates its arguments; quoting an argument defeats evaluation. `fortran` always returns `done`.

  See also the function `f90` for printing one or more expressions as a Fortran 90 program.

  Examples:

      (%i1) expr: (a + b)^12$
      (%i2) fortran (expr);
            (b+a)**12
      (%o2)                         done
      (%i3) fortran ('x=expr);
            x = (b+a)**12
      (%o3)                         done
      (%i4) fortran ('x=expand (expr));
            x = b**12+12*a*b**11+66*a**2*b**10+220*a**3*b**9+495*a**4*b**8+792
           1   *a**5*b**7+924*a**6*b**6+792*a**7*b**5+495*a**8*b**4+220*a**9*b
           2   **3+66*a**10*b**2+12*a**11*b+a**12
      (%o4)                         done
      (%i5) fortran ('x=7+5*%i);
            x = (7,5)
      (%o5)                         done
      (%i6) fortran ('x=[1,2,3,4]);
            x = [1,2,3,4]
      (%o6)                         done
      (%i7) f(x) := x^2$
      (%i8) fortran (f);
            f
      (%o8)                         done

  ·

  @ref{Category: Translation and compilation}

Option variable: fortspaces

  Default value: `false`

  When `fortspaces` is `true`, `fortran` fills out each printed line with spaces to 80 columns.

  ·

  @ref{Category: Translation and compilation}

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