Introduction for Runtime Environment
====================================

maxima-init.mac is a file which is loaded automatically when Maxima starts. You can use maxima-init.mac to customize your Maxima environment. maxima-init.mac, if it exists, is typically placed in the directory named by maxima_userdir, although it can be in any directory searched by the function file_search.

Here is an example maxima-init.mac file:

     setup_autoload ("specfun.mac", ultraspherical, assoc_legendre_p);
     showtime:all;

In this example, setup_autoload tells Maxima to load the specified file (specfun.mac) if any of the functions (ultraspherical, assoc_legendre_p) are called but not yet defined. Thus you needn't remember to load the file before calling the functions.

The statement showtime: all tells Maxima to set the showtime variable. The maxima-init.mac file can contain any other assignments or other Maxima statements.

Interrupts
==========

The user can stop a time-consuming computation with the ^C (control-C) character. The default action is to stop the computation and print another user prompt. In this case, it is not possible to restart a stopped computation.

If the Lisp variable *debugger-hook* is set to nil, by executing

     :lisp (setq *debugger-hook* nil)

then upon receiving ^C, Maxima will enter the Lisp debugger, and the user may use the debugger to inspect the Lisp environment. The stopped computation can be restarted by entering continue in the Lisp debugger. The means of returning to Maxima from the Lisp debugger (other than running the computation to completion) is different for each version of Lisp.

On Unix systems, the character ^Z (control-Z) causes Maxima to stop altogether, and control is returned to the shell prompt. The fg command causes Maxima to resume from the point at which it was stopped.

Functions and Variables for Runtime Environment
===============================================

 -- Declaration: feature
     Maxima understands two distinct types of features, system features and features which apply to mathematical expressions. See also status for information about system features. See also features and featurep for information about mathematical features.

     feature itself is not the name of a function or variable.

 -- Function: featurep (A, F)
     Attempts to determine whether the object A has the feature F on the basis of the facts in the current database.  If so, it returns true, else false.

     Note that featurep returns false when neither F nor the negation of F can be established.

     featurep evaluates its argument.

     See also declare and features.

          (%i1) declare (j, even)$
          (%i2) featurep (j, integer);
          (%o2)                           true

 -- System variable: maxima_tempdir

     maxima_tempdir names the directory in which Maxima creates some temporary files. In particular, temporary files for plotting are created in maxima_tempdir.

     The initial value of maxima_tempdir is the user's home directory, if Maxima can locate it; otherwise Maxima makes a guess about a suitable directory.

     maxima_tempdir may be assigned a string which names a directory.

 -- System variable: maxima_userdir

     maxima_userdir names a directory which Maxima searches to find Maxima and Lisp files. (Maxima searches some other directories as well; file_search_maxima and file_search_lisp are the complete lists.)

     The initial value of maxima_userdir is a subdirectory of the user's home directory, if Maxima can locate it; otherwise Maxima makes a guess about a suitable directory.

     maxima_userdir may be assigned a string which names a directory. However, assigning to maxima_userdir does not automatically change file_search_maxima and file_search_lisp; those variables must be changed separately.

 -- Function: room ()
 -- Function: room (true)
 -- Function: room (false)
     Prints out a description of the state of storage and stack management in Maxima. room calls the Lisp function of the same name.

       * room () prints out a moderate description.

       * room (true) prints out a verbose description.

       * room (false) prints out a terse description.

 -- Function: status (feature)
 -- Function: status (feature, PUTATIVE_FEATURE)
 -- Function: status (status)
     Returns information about the presence or absence of certain system-dependent features.

       * status (feature) returns a list of system features. These include Lisp version, operating system type, etc. The list may vary from one Lisp type to another.

       * status (feature, PUTATIVE_FEATURE) returns true if PUTATIVE_FEATURE is on the list of items returned by status (feature) and false otherwise. status quotes the argument PUTATIVE_FEATURE. The quote-quote operator '' defeats quotation. A feature whose name contains a special character, such as a hyphen, must be given as a string argument. For example, status (feature, "ansi-cl").

       * status (status) returns a two-element list [feature, status]. feature and status are the two arguments accepted by the status function; it is unclear if this list has additional significance.

     The variable features contains a list of features which apply to mathematical expressions. See features and featurep for more information.

 -- Function: time (%o1, %o2, %o3, ...)
     Returns a list of the times, in seconds, taken to compute the output lines %o1, %o2, %o3, .... The time returned is Maxima's estimate of the internal computation time, not the elapsed time. time can only be applied to output line variables; for any other variables, time returns unknown.

     Set showtime: true to make Maxima print out the computation time and elapsed time with each output line.

 -- Function: timedate ()
     Returns a string representing the current time and date. The string has the format HH:MM:SS Day, mm/dd/yyyy (GMT-n), where the fields are hours, minutes, seconds, day of week, month, day of month, year, and hours different from GMT.

     The return value is a Lisp string.

     Example:

          (%i1) d: timedate ();
          (%o1) 08:05:09 Wed, 11/02/2005 (GMT-7)
          (%i2) print ("timedate reports current time", d)$
          timedate reports current time 08:05:09 Wed, 11/02/2005 (GMT-7)

 -- Function: absolute_real_time ()

     Returns the number of seconds since midnight, January 1, 1900 UTC. The return value is an integer.

     See also elapsed_real_time and elapsed_run_time.

     Example:

          (%i1) absolute_real_time ();
          (%o1)                      3385045277
          (%i2) 1900 + absolute_real_time () / (365.25 * 24 * 3600);
          (%o2)                   2007.265612087104

 -- Function: elapsed_real_time ()

     Returns the number of seconds (including fractions of a second) since Maxima was most recently started or restarted. The return value is a floating-point number.

     See also absolute_real_time and elapsed_run_time.

     Example:

          (%i1) elapsed_real_time ();
          (%o1)                       2.559324
          (%i2) expand ((a + b)^500)$
          (%i3) elapsed_real_time ();
          (%o3)                       7.552087

 -- Function: elapsed_run_time ()

     Returns an estimate of the number of seconds (including fractions of a second) which Maxima has spent in computations since Maxima was most recently started or restarted. The return value is a floating-point number.

     See also absolute_real_time and elapsed_real_time.

     Example:

          (%i1) elapsed_run_time ();
          (%o1)                         0.04
          (%i2) expand ((a + b)^500)$
          (%i3) elapsed_run_time ();
          (%o3)                         1.26