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32. Runtime Environment


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32.1 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.

Categories:  Session management


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32.2 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.

Categories:  Console interaction


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32.3 Functions and Variables for Runtime Environment

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.

Categories:  Global variables

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.

Categories:  Global variables

Function: room  
    room ()  
    room (true)  
    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.

Categories:  Debugging

Function: sstatus (keyword, item)

When keyword is the symbol feature, item is put on the list of system features. After sstatus (keyword, item) is executed, status (feature, item) returns true. If keyword is the symbol nofeature, item is deleted from the list of system features. This can be useful for package writers, to keep track of what features they have loaded in.

See also status.

Categories:  Programming

Function: status  
    status (feature)  
    status (feature, item)

Returns information about the presence or absence of certain system-dependent features.

See also sstatus.

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

Categories:  Programming

Function: system (command)

Executes command as a separate process. The command is passed to the default shell for execution. system is not supported by all operating systems, but generally exists in Unix and Unix-like environments.

Supposing _hist.out is a list of frequencies which you wish to plot as a bar graph using xgraph.

(%i1) (with_stdout("_hist.out",
           for i:1 thru length(hist) do (
             print(i,hist[i]))),
       system("xgraph -bar -brw .7 -nl < _hist.out"));

In order to make the plot be done in the background (returning control to Maxima) and remove the temporary file after it is done do:

system("(xgraph -bar -brw .7 -nl < _hist.out;  rm -f _hist.out)&")

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.

Categories:  Debugging

Function: timedate  
    timedate (T, tz_offset)

    timedate (T)
    timedate ()  

timedate(T, tz_offset) returns a string representing the time T in the time zone tz_offset. The string format is YYYY-MM-DD HH:MM:SS.NNN[+|-]ZZ:ZZ (using as many digits as necessary to represent the fractional part) if T has a nonzero fractional part, or YYYY-MM-DD HH:MM:SS[+|-]ZZ:ZZ if its fractional part is zero.

T measures time, in seconds, since midnight, January 1, 1900, in the GMT time zone.

tz_offset measures the offset of the time zone, in hours, east (positive) or west (negative) of GMT. tz_offset must be an integer, rational, or float between -24 and 24, inclusive. If tz_offset is not a multiple of 1/60, it is rounded to the nearest multiple of 1/60.

timedate(T) is equivalent to timedate(T, tz_offset) with tz_offset equal to the offset of the local time zone.

timedate() is equivalent to timedate(absolute_real_time()). That is, it returns the current time in the local time zone.

Example:

timedate with no argument returns a string representing the current time and date.

(%i1) d : timedate ();
(%o1)                      2010-06-08 04:08:09+01:00
(%i2) print ("timedate reports current time", d) $
timedate reports current time 2010-06-08 04:08:09+01:00

timedate with an argument returns a string representing the argument.

(%i1) timedate (0);
(%o1)                      1900-01-01 01:00:00+01:00
(%i2) timedate (absolute_real_time () - 7*24*3600);
(%o2)                      2010-06-01 04:19:51+01:00

timedate with optional timezone offset.

(%i1) timedate (1000000000, -9.5);
(%o1)               1931-09-09 16:16:40-09:30

Categories:  Time and date functions

Function: parse_timedate  
    parse_timedate (S)

Parses a string S representing a date or date and time of day and returns the number of seconds since midnight, January 1, 1900 GMT. If there is a nonzero fractional part, the value returned is a rational number, otherwise, it is an integer. parse_timedate returns false if it cannot parse S according to any of the allowed formats.

The string S must have one of the following formats, optionally followed by a timezone designation:

where the fields are year, month, day, hours, minutes, seconds, and fraction of a second, and square brackets indicate acceptable alternatives. The fraction may contain one or more digits.

Except for the fraction of a second, each field must have exactly the number of digits indicated: four digits for the year, and two for the month, day of the month, hours, minutes, and seconds.

A timezone designation must have one of the following forms:

where hh and mm indicate hours and minutes east (+) or west (-) of GMT. The timezone may be from +24 hours (inclusive) to -24 hours (inclusive).

A literal character Z is equivalent to +00:00 and its variants, indicating GMT.

If no timezone is indicated, the time is assumed to be in the local time zone.

Any leading or trailing whitespace (space, tab, newline, and carriage return) is ignored, but any other leading or trailing characters cause parse_timedate to fail and return false.

See also timedate and absolute_real_time.

Examples:

Midnight, January 1, 1900, in the local time zone, in each acceptable format. The result is the number of seconds the local time zone is ahead (negative result) or behind (positive result) GMT. In this example, the local time zone is 8 hours behind GMT.

(%i1) parse_timedate ("1900-01-01 00:00:00,000");
(%o1)                         28800
(%i2) parse_timedate ("1900-01-01 00:00:00.000");
(%o2)                         28800
(%i3) parse_timedate ("1900-01-01T00:00:00,000");
(%o3)                         28800
(%i4) parse_timedate ("1900-01-01T00:00:00.000");
(%o4)                         28800
(%i5) parse_timedate ("1900-01-01 00:00:00");
(%o5)                         28800
(%i6) parse_timedate ("1900-01-01T00:00:00");
(%o6)                         28800
(%i7) parse_timedate ("1900-01-01");
(%o7)                         28800

Midnight, January 1, 1900, GMT, in different indicated time zones.

(%i1) parse_timedate ("1900-01-01 19:00:00+19:00");
(%o1)                           0
(%i2) parse_timedate ("1900-01-01 07:00:00+07:00");
(%o2)                           0
(%i3) parse_timedate ("1900-01-01 01:00:00+01:00");
(%o3)                           0
(%i4) parse_timedate ("1900-01-01Z");
(%o4)                           0
(%i5) parse_timedate ("1899-12-31 21:00:00-03:00");
(%o5)                           0
(%i6) parse_timedate ("1899-12-31 13:00:00-11:00");
(%o6)                           0
(%i7) parse_timedate ("1899-12-31 08:00:00-16:00");
(%o7)                           0

Categories:  Time and date functions

Function: encode_time  
    encode_time (year, month, day, hours, minutes, seconds, tz_offset)  
    encode_time (year, month, day, hours, minutes, seconds)

Given a time and date specified by year, month, day, hours, minutes, and seconds, encode_time returns the number of seconds (possibly including a fractional part) since midnight, January 1, 1900 GMT.

year must be an integer greater than or equal to 1899. However, 1899 is allowed only if the resulting encoded time is greater than or equal to 0.

month must be an integer from 1 to 12, inclusive.

day must be an integer from 1 to n, inclusive, where n is the number of days in the month specified by month.

hours must be an integer from 0 to 23, inclusive.

minutes must be an integer from 0 to 59, inclusive.

seconds must be an integer, rational, or float greater than or equal to 0 and less than 60. When seconds is not an integer, encode_time returns a rational, such that the fractional part of the return value is equal to the fractional part of seconds. Otherwise, seconds is an integer, and the return value is likewise an integer.

tz_offset measures the offset of the time zone, in hours, east (positive) or west (negative) of GMT. tz_offset must be an integer, rational, or float between -24 and 24, inclusive. If tz_offset is not a multiple of 1/3600, it is rounded to the nearest multiple of 1/3600.

If tz_offset is not present, the offset of the local time zone is assumed.

See also decode_time.

Examples:

(%i1) encode_time (1900, 1, 1, 0, 0, 0, 0);
(%o1)                           0
(%i2) encode_time (1970, 1, 1, 0, 0, 0, 0);
(%o2)                      2208988800
(%i3) encode_time (1970, 1, 1, 8, 30, 0, 8.5);
(%o3)                      2208988800
(%i4) encode_time (1969, 12, 31, 16, 0, 0, -8);
(%o4)                      2208988800
(%i5) encode_time (1969, 12, 31, 16, 0, 1/1000, -8);
                          2208988800001
(%o5)                     -------------
                              1000
(%i6) % - 2208988800;
                               1
(%o6)                         ----
                              1000

Categories:  Time and date functions

Function: decode_time  
    decode_time (T, tz_offset)  
    decode_time (T)

Given the number of seconds (possibly including a fractional part) since midnight, January 1, 1900 GMT, returns the date and time as represented by a list comprising the year, month, day of the month, hours, minutes, seconds, and time zone offset.

tz_offset measures the offset of the time zone, in hours, east (positive) or west (negative) of GMT. tz_offset must be an integer, rational, or float between -24 and 24, inclusive. If tz_offset is not a multiple of 1/3600, it is rounded to the nearest multiple of 1/3600.

If tz_offset is not present, the offset of the local time zone is assumed.

See also encode_time.

Examples:

(%i1) decode_time (0, 0);
(%o1)               [1900, 1, 1, 0, 0, 0, 0]
(%i2) decode_time (0);
(%o2)             [1899, 12, 31, 16, 0, 0, - 8]
(%i3) decode_time (2208988800, 9.25);
                                          37
(%o3)              [1970, 1, 1, 9, 15, 0, --]
                                          4
(%i4) decode_time (2208988800);
(%o4)             [1969, 12, 31, 16, 0, 0, - 8]
(%i5) decode_time (2208988800 + 1729/1000, -6);
                                      1729
(%o5)           [1969, 12, 31, 18, 0, ----, - 6]
                                      1000
(%i6) decode_time (2208988800 + 1729/1000);
                                      1729
(%o6)           [1969, 12, 31, 16, 0, ----, - 8]
                                      1000

Categories:  Time and date functions

Function: absolute_real_time ()

Returns the number of seconds since midnight, January 1, 1900 GMT. 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

Categories:  Time and date functions

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

Categories:  Time and date functions

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

Categories:  Time and date functions


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