### 4.2 Functions and Variables for Command Line

System variable: __

  `__` is the input expression currently being evaluated. That is, while an input expression expr is being evaluated, `__` is expr.

  `__` is assigned the input expression before the input is simplified or evaluated. However, the value of `__` is simplified (but not evaluated) when it is displayed.

  `__` is recognized by `batch` and `load`. In a file processed by `batch`, `__` has the same meaning as at the interactive prompt. In a file processed by `load`, `__` is bound to the input expression most recently entered at the interactive prompt or in a batch file; `__` is not bound to the input expressions in the file being processed. In particular, when `load (filename)` is called from the interactive prompt, `__` is bound to `load (filename)` while the file is being processed.

  See also `_` and `%`.

  Examples:

      (%i1) print ("I was called as", __);
      I was called as print(I was called as, __)
      (%o1)              print(I was called as, __)

      (%i2) foo (__);
      (%o2)                     foo(foo(__))

      (%i3) g (x) := (print ("Current input expression =", __), 0);
      (%o3) g(x) := (print("Current input expression =", __), 0)

      (%i4) [aa : 1, bb : 2, cc : 3];
      (%o4)                       [1, 2, 3]

      (%i5) (aa + bb + cc)/(dd + ee + g(x));
                                  cc + bb + aa
      Current input expression = --------------
                                 g(x) + ee + dd
                                      6
      (%o5)                        -------
                                   ee + dd

  Categories:Global variables ·

System variable: _

  `_` is the most recent input expression (e.g., `%i1`, `%i2`, `%i3`, …).

  `_` is assigned the input expression before the input is simplified or evaluated. However, the value of `_` is simplified (but not evaluated) when it is displayed.

  `_` is recognized by `batch` and `load`. In a file processed by `batch`, `_` has the same meaning as at the interactive prompt. In a file processed by `load`, `_` is bound to the input expression most recently evaluated at the interactive prompt or in a batch file; `_` is not bound to the input expressions in the file being processed.

  See also `__` and `%`.

  Examples:

      (%i1) 13 + 29;
      (%o1)                          42

      (%i2) :lisp $_
      ((MPLUS) 13 29)

      (%i2) _;
      (%o2)                          42

      (%i3) sin (%pi/2);
      (%o3)                           1

      (%i4) :lisp $_
      ((%SIN) ((MQUOTIENT) $%PI 2))

      (%i4) _;
      (%o4)                           1

      (%i5) a: 13$
      (%i6) b: 29$

      (%i7) a + b;
      (%o7)                          42

      (%i8) :lisp $_
      ((MPLUS) $A $B)

      (%i8) _;
      (%o8)                         b + a

      (%i9) a + b;
      (%o9)                          42

      (%i10) ev (_);
      (%o10)                         42

  Categories:Console interaction ·Global variables ·

System variable: %

  `%` is the output expression (e.g., `%o1`, `%o2`, `%o3`, …) most recently computed by Maxima, whether or not it was displayed.

  `%` is recognized by `batch` and `load`. In a file processed by `batch`, `%` has the same meaning as at the interactive prompt. In a file processed by `load`, `%` is bound to the output expression most recently computed at the interactive prompt or in a batch file; `%` is not bound to output expressions in the file being processed.

  See also `_`, `%%`, and `%th`.

  Categories:Console interaction ·Global variables ·

System variable: %%

  In compound statements, namely `block`, `lambda`, or `(s_1, ..., s_n)`, `%%` is the value of the previous statement.

  At the first statement in a compound statement, or outside of a compound statement, `%%` is undefined.

  `%%` is recognized by `batch` and `load`, and it has the same meaning as at the interactive prompt.

  See also `%`.

  Examples:

  The following two examples yield the same result.

      (%i1) block (integrate (x^5, x), ev (%%, x=2) - ev (%%, x=1));
                                     21
      (%o1)                          --
                                     2
      (%i2) block ([prev], prev: integrate (x^5, x),
                     ev (prev, x=2) - ev (prev, x=1));
                                     21
      (%o2)                          --
                                     2

  A compound statement may comprise other compound statements. Whether a statement be simple or compound, `%%` is the value of the previous statement.

      (%i3) block (block (a^n, %%*42), %%/6);
                                       n
      (%o3)                         7 a

  Within a compound statement, the value of `%%` may be inspected at a break prompt, which is opened by executing the `break` function. For example, entering `%%;` in the following example yields `42`.

      (%i4) block (a: 42, break ())$

      Entering a Maxima break point. Type 'exit;' to resume.
      _%%;
      42
      _

  Categories:Global variables ·

Function: %th (i)

  The value of the i’th previous output expression. That is, if the next expression to be computed is the n’th output, `%th (m)` is the (n - m)’th output.

  `%th` is recognized by `batch` and `load`. In a file processed by `batch`, `%th` has the same meaning as at the interactive prompt. In a file processed by `load`, `%th` refers to output expressions most recently computed at the interactive prompt or in a batch file; `%th` does not refer to output expressions in the file being processed.

  See also `%` and `%%`.

  Example:

  `%th` is useful in `batch` files or for referring to a group of output expressions. This example sets `s` to the sum of the last five output expressions.

      (%i1) 1;2;3;4;5;
      (%o1)                           1
      (%o2)                           2
      (%o3)                           3
      (%o4)                           4
      (%o5)                           5
      (%i6) block (s: 0, for i:1 thru 5 do s: s + %th(i), s);
      (%o6)                          15

  Categories:Console interaction ·

Special symbol: ?

  As prefix to a function or variable name, `?` signifies that the name is a Lisp name, not a Maxima name. For example, `?round` signifies the Lisp function `ROUND`. See Lisp and Maxima for more on this point.

  The notation `? word` (a question mark followed a word, separated by whitespace) is equivalent to `describe("word")`. The question mark must occur at the beginning of an input line; otherwise it is not recognized as a request for documentation. See also `describe`.

  Categories:Help ·Console interaction ·

Special symbol: ??

  The notation `?? word` (`??` followed a word, separated by whitespace) is equivalent to `describe("word", inexact)`. The question mark must occur at the beginning of an input line; otherwise it is not recognized as a request for documentation. See also `describe`.

  Categories:Help ·Console interaction ·

Input terminator: $

  The dollar sign `$` terminates an input expression, and the most recent output `%` and an output label, e.g. `%o1`, are assigned the result, but the result is not displayed.

  See also `;`.

  Example:

      (%i1) 1 + 2 + 3 $

      (%i2) %;
      (%o2)                           6

      (%i3) %o1;
      (%o3)                           6

Input terminator: ;

  The semicolon `;` terminates an input expression, and the resulting output is displayed.

  See also `$`.

  Example:

      (%i1) 1 + 2 + 3;
      (%o1)                           6

Option variable: inchar

  Default value: `%i`

  `inchar` is the prefix of the labels of expressions entered by the user. Maxima automatically constructs a label for each input expression by concatenating `inchar` and `linenum`.

  `inchar` may be assigned any string or symbol, not necessarily a single character. Because Maxima internally takes into account only the first char of the prefix, the prefixes `inchar`, `outchar`, and `linechar` should have a different first char. Otherwise some commands like `kill(inlabels)` do not work as expected.

  See also `labels`.

  Example:

      (%i1) inchar: "input";
      (%o1)                         input

      (input2) expand((a+b)^3);
                           3        2      2      3
      (%o2)               b  + 3 a b  + 3 a  b + a

  Categories:Display flags and variables ·

System variable: infolists

  Default value: `[]`

  `infolists` is a list of the names of all of the information lists in Maxima. These are:

  `labels`

    All bound `%i`, `%o`, and `%t` labels.

  `values`

    All bound atoms which are user variables, not Maxima options or switches, created by `:` or `::` or functional binding.

  `functions`

    All user-defined functions, created by `:=` or `define`.

  `arrays`

    All arrays, `hashed arrays` and `memoizing functions`.

  `macros`

    All user-defined macro functions, created by `::=`.

  `myoptions`

    All options ever reset by the user (whether or not they are later reset to their default values).

  `rules`

    All user-defined pattern matching and simplification rules, created by `tellsimp`, `tellsimpafter`, `defmatch`, or `defrule`.

  `aliases`

    All atoms which have a user-defined alias, created by the `alias`, `ordergreat`, `orderless` functions or by declaring the atom as a `noun` with `declare`.

  `dependencies`

    All atoms which have functional dependencies, created by the `depends`, `dependencies`, or `gradef` functions.

  `gradefs`

    All functions which have user-defined derivatives, created by the `gradef` function.

  `props`

    All atoms which have any property other than those mentioned above, such as properties established by `atvalue` or `matchdeclare`, etc., as well as properties established in the `declare` function.

  `structures`

    All structs defined using `defstruct`.

  `let_rule_packages`

    All user-defined `let` rule packages plus the special package `default_let_rule_package`. (`default_let_rule_package` is the name of the rule package used when one is not explicitly set by the user.)

  Categories:Declarations and inferences ·Global variables ·

Function: kill
`kill` (a_1, …, a_n)
`kill` (labels)
`kill` (inlabels, outlabels, linelabels)
`kill` (n)
`kill` ([m, n])
`kill` (values, functions, arrays, …)
`kill` (all)
`kill` (allbut (a_1, …, a_n))

  Removes all bindings (value, function, array, or rule) from the arguments a_1, …, a_n. An argument a_k may be a symbol or a single array element. When a_k is a single array element, `kill` unbinds that element without affecting any other elements of the array.

  Several special arguments are recognized. Different kinds of arguments may be combined, e.g., `kill (inlabels, functions, allbut (foo, bar))`.

  `kill (labels)` unbinds all input, output, and intermediate expression labels created so far. `kill (inlabels)` unbinds only input labels which begin with the current value of `inchar`. Likewise, `kill (outlabels)` unbinds only output labels which begin with the current value of `outchar`, and `kill (linelabels)` unbinds only intermediate expression labels which begin with the current value of `linechar`.

  `kill (n)`, where n is an integer, unbinds the n most recent input and output labels.

  `kill ([m, n])` unbinds input and output labels m through n.

  `kill (infolist)`, where infolist is any item in `infolists` (such as `values`, `functions`, or `arrays`) unbinds all items in infolist. See also `infolists`.

  `kill (all)` unbinds all items on all infolists. `kill (all)` does not reset global variables to their default values; see `reset` on this point.

  `kill (allbut (a_1, ..., a_n))` unbinds all items on all infolists except for a_1, …, a_n. `kill (allbut (infolist))` unbinds all items except for the ones on infolist, where infolist is `values`, `functions`, `arrays`, etc.

  The memory taken up by a bound property is not released until all symbols are unbound from it. In particular, to release the memory taken up by the value of a symbol, one unbinds the output label which shows the bound value, as well as unbinding the symbol itself.

  `kill` quotes its arguments. The quote-quote operator `''` defeats quotation.

  `kill (symbol)` unbinds all properties of symbol. In contrast, the functions `remvalue`, `remfunction`, `remarray`, and `remrule` unbind a specific property. Note that facts declared by `assume` don’t require a symbol they apply to, therefore aren’t stored as properties of symbols and therefore aren’t affected by `kill`.

  `kill` always returns `done`, even if an argument has no binding.

  Categories:Evaluation ·Console interaction ·Session management ·

Function: labels (symbol)

  Returns the list of input, output, or intermediate expression labels which begin with symbol. Typically symbol is the value of `inchar`, `outchar`, or `linechar`. If no labels begin with symbol, `labels` returns an empty list.

  By default, Maxima displays the result of each user input expression, giving the result an output label. The output display is suppressed by terminating the input with `$` (dollar sign) instead of `;` (semicolon). An output label is constructed and bound to the result, but not displayed, and the label may be referenced in the same way as displayed output labels. See also `%`, `%%`, and `%th`.

  Intermediate expression labels can be generated by some functions. The option variable `programmode` controls whether `solve` and some other functions generate intermediate expression labels instead of returning a list of expressions. Some other functions, such as `ldisplay`, always generate intermediate expression labels.

  See also `inchar`, `outchar`, `linechar`, and `infolists`.

  Categories:Display functions ·Console interaction ·

System variable: labels

  The variable `labels` is the list of input, output, and intermediate expression labels, including all previous labels if `inchar`, `outchar`, or `linechar` were redefined.

  Categories:Display flags and variables ·Console interaction ·

Option variable: linechar

  Default value: `%t`

  `linechar` is the prefix of the labels of intermediate expressions generated by Maxima. Maxima constructs a label for each intermediate expression (if displayed) by concatenating `linechar` and `linenum`.

  `linechar` may be assigned any string or symbol, not necessarily a single character. Because Maxima internally takes into account only the first char of the prefix, the prefixes `inchar`, `outchar`, and `linechar` should have a different first char. Otherwise some commands like `kill(inlabels)` do not work as expected.

  Intermediate expressions might or might not be displayed. See `programmode` and `labels`.

  Categories:Display flags and variables ·

System variable: linenum

  The line number of the current pair of input and output expressions.

  Categories:Display flags and variables ·Console interaction ·

System variable: myoptions

  Default value: `[]`

  `myoptions` is the list of all options ever reset by the user, whether or not they get reset to their default value.

  Categories:Global variables ·Session management ·Console interaction ·

Option variable: nolabels

  Default value: `false`

  When `nolabels` is `true`, input and output result labels (`%i` and `%o`, respectively) are displayed, but the labels are not bound to results, and the labels are not appended to the `labels` list. Since labels are not bound to results, garbage collection can recover the memory taken up by the results.

  Otherwise input and output result labels are bound to results, and the labels are appended to the `labels` list.

  Intermediate expression labels (`%t`) are not affected by `nolabels`; whether `nolabels` is `true` or `false`, intermediate expression labels are bound and appended to the `labels` list.

  See also `batch`, `load`, and `labels`.

  Categories:Global flags ·Session management ·

Option variable: optionset

  Default value: `false`

  When `optionset` is `true`, Maxima prints out a message whenever a Maxima option is reset. This is useful if the user is doubtful of the spelling of some option and wants to make sure that the variable he assigned a value to was truly an option variable.

  Example:

      (%i1) optionset:true;
      assignment: assigning to option optionset
      (%o1)                         true
      (%i2) gamma_expand:true;
      assignment: assigning to option gamma_expand
      (%o2)                         true

  Categories:Global flags ·Session management ·Console interaction ·

Option variable: outchar

  Default value: `%o`

  `outchar` is the prefix of the labels of expressions computed by Maxima. Maxima automatically constructs a label for each computed expression by concatenating `outchar` and `linenum`.

  `outchar` may be assigned any string or symbol, not necessarily a single character. Because Maxima internally takes into account only the first char of the prefix, the prefixes `inchar`, `outchar` and `linechar` should have a different first char. Otherwise some commands like `kill(inlabels)` do not work as expected.

  See also `labels`.

  Example:

      (%i1) outchar: "output";
      (output1)                    output

      (%i2) expand((a+b)^3);
                           3        2      2      3
      (output2)           b  + 3 a b  + 3 a  b + a

  Categories:Display flags and variables ·

Function: playback
`playback` ()
`playback` (n)
`playback` ([m, n])
`playback` ([m])
`playback` (input)
`playback` (slow)
`playback` (time)
`playback` (grind)

  Displays input, output, and intermediate expressions, without recomputing them. `playback` only displays the expressions bound to labels; any other output (such as text printed by `print` or `describe`, or error messages) is not displayed. See also `labels`.

  `playback` quotes its arguments. The quote-quote operator `''` defeats quotation. `playback` always returns `done`.

  `playback ()` (with no arguments) displays all input, output, and intermediate expressions generated so far. An output expression is displayed even if it was suppressed by the `$` terminator when it was originally computed.

  `playback (n)` displays the most recent n expressions. Each input, output, and intermediate expression counts as one.

  `playback ([m, n])` displays input, output, and intermediate expressions with numbers from m through n, inclusive.

  `playback ([m])` is equivalent to `playback ([m, m])`; this usually prints one pair of input and output expressions.

  `playback (input)` displays all input expressions generated so far.

  `playback (slow)` pauses between expressions and waits for the user to press `enter`. This behavior is similar to `demo`. `playback (slow)` is useful in conjunction with `save` or `stringout` when creating a secondary-storage file in order to pick out useful expressions.

  `playback (time)` displays the computation time for each expression.

  `playback (grind)` displays input expressions in the same format as the `grind` function. Output expressions are not affected by the `grind` option. See `grind`.

  Arguments may be combined, e.g., `playback ([5, 10], grind, time, slow)`.

  Categories:Display functions ·Console interaction ·

Option variable: prompt

  Default value: `_`

  `prompt` is the prompt symbol of the `demo` function, `playback (slow)` mode, and the Maxima break loop (as invoked by `break`).

  Categories:Global variables ·Console interaction ·

Function: quit ()

  Terminates the Maxima session. Note that the function must be invoked as `quit();` or `quit()$`, not `quit` by itself.

  To stop a lengthy computation, type `control-C`. The default action is to return to the Maxima prompt. If `*debugger-hook*` is `nil`, `control-C` opens the Lisp debugger. See also Debugging.

  Categories:Console interaction ·

Function: read (expr_1, …, expr_n)

  Prints expr_1, …, expr_n, then reads one expression from the console and returns the evaluated expression. The expression is terminated with a semicolon `;` or dollar sign `$`.

  See also `readonly`

  Example:

      (%i1) foo: 42$
      (%i2) foo: read ("foo is", foo, " -- enter new value.")$
      foo is 42  -- enter new value.
      (a+b)^3;
      (%i3) foo;
                                           3
      (%o3)                         (b + a)

  Categories:Console interaction ·

Function: readonly (expr_1, …, expr_n)

  Prints expr_1, …, expr_n, then reads one expression from the console and returns the expression (without evaluation). The expression is terminated with a `;` (semicolon) or `$` (dollar sign).

  See also `read`.

  Examples:

      (%i1) aa: 7$
      (%i2) foo: readonly ("Enter an expression:");
      Enter an expression:
      2^aa;
                                        aa
      (%o2)                            2
      (%i3) foo: read ("Enter an expression:");
      Enter an expression:
      2^aa;
      (%o3)                            128

  Categories:Console interaction ·

Function: reset ()

  Resets many global variables and options, and some other variables, to their default values.

  `reset` processes the variables on the Lisp list `*variable-initial-values*`. The Lisp macro `defmvar` puts variables on this list (among other actions). Many, but not all, global variables and options are defined by `defmvar`, and some variables defined by `defmvar` are not global variables or options.

  Categories:Session management ·

Option variable: showtime

  Default value: `false`

  When `showtime` is `true`, the computation time and elapsed time is printed with each output expression.

  The computation time is always recorded, so `time` and `playback` can display the computation time even when `showtime` is `false`.

  See also `timer`.

  Categories:Display flags and variables ·Debugging ·

Function: to_lisp ()

  Enters the Lisp system under Maxima. `(to-maxima)` returns to Maxima.

  Example:

  Define a function and enter the Lisp system under Maxima. The definition is inspected on the property list, then the function definition is extracted, factored and stored in the variable `$result`. The variable can be used in Maxima after returning to Maxima.

      (%i1) f(x):=x^2+x;
                                        2
      (%o1)                    f(x) := x  + x
      (%i2) to_lisp();
      Type (to-maxima) to restart, ($quit) to quit Maxima.
      MAXIMA> (symbol-plist '$f)
      (MPROPS (NIL MEXPR ((LAMBDA) ((MLIST) $X)
                                   ((MPLUS) ((MEXPT) $X 2) $X))))
      MAXIMA> (setq $result ($factor (caddr (mget '$f 'mexpr))))
      ((MTIMES SIMP FACTORED) $X ((MPLUS SIMP IRREDUCIBLE) 1 $X))
      MAXIMA> (to-maxima)
      Returning to Maxima
      (%o2)                         true
      (%i3) result;
      (%o3)                       x (x + 1)

  Categories:Console interaction ·

Function: eval_string_lisp (str)

  Sequentially read lisp forms from the string str and evaluate them. Any values produced from the last form are returned as a Maxima list.

  Examples:

      (%i1) eval_string_lisp ("");
      (%o1) []

      (%i2) eval_string_lisp ("(values)");
      (%o2) []

      (%i3) eval_string_lisp ("69");
      (%o3) [69]

      (%i4) eval_string_lisp ("1 2 3");
      (%o4) [3]

      (%i5) eval_string_lisp ("(values 1 2 3)");
      (%o5) [1,2,3]

      (%i6) eval_string_lisp ("(defun $foo (x) (* 2 x))");
      (%o6) [foo]

      (%i7) foo (5);
      (%o7) 10

  See also eval_string.

  Categories:Debugging ·Evaluation ·

System variable: values

  Initial value: `[]`

  `values` is a list of all bound user variables (not Maxima options or switches). The list comprises symbols bound by `:`, or `::`.

  If the value of a variable is removed with the commands `kill`, `remove`, or `remvalue` the variable is deleted from `values`.

  See `functions` for a list of user defined functions.

  Examples:

  First, `values` shows the symbols `a`, `b`, and `c`, but not `d`, it is not bound to a value, and not the user function `f`. The values are removed from the variables. `values` is the empty list.

      (%i1) [a:99, b:: a-90, c:a-b, d, f(x):=x^2];
                                                 2
      (%o1)              [99, 9, 90, d, f(x) := x ]

      (%i2) values;
      (%o2)                       [a, b, c]

      (%i3) [kill(a), remove(b,value), remvalue(c)];
      (%o3)                   [done, done, [c]]

      (%i4) values;
      (%o4)                          []

  Categories:Evaluation ·Global variables ·