User Level Required: interpreter
Command Syntax:
- )history )on
- )history )off
- )history )write historyInputFileName
- )history )show [n] [both]
- )history )save savedHistoryName
- )history )restore [savedHistoryName]
- )history )reset
- )history )change n
- )history )memory
- )history )file
- %
- %%(n)
- )set history on | off
Command Description:
The history facility within FriCAS allows you to restore your environment to that of another session and recall previous computational results. Additional commands allow you to review previous input lines and to create an .input file of the lines typed to FriCAS.
FriCAS saves your input and output if the history facility is turned on (which is the default). This information is saved if either of
)set history on
)history )on
has been issued. Issuing either
)set history off
)history )off
will discontinue the recording of information.
Whether the facility is disabled or not, the value of % in FriCAS always refers to the result of the last computation. If you have not yet entered anything, % evaluates to an object of type Variable(‘%). The function %% may be used to refer to other previous results if the history facility is enabled. In that case, %%(n) is the output from step n if n > 0. If n < 0, the step is computed relative to the current step. Thus %%(-1) is also the previous step, %%(-2), is the step before that, and so on. If an invalid step number is given, FriCAS will signal an error.
The environment information can either be saved in a file or entirely in memory (the default). Each frame ( description of command )frame ) has its own history database. When it is kept in a file, some of it may also be kept in memory for efficiency. When the information is saved in a file, the name of the file is of the form FRAME.axh where FRAME is the name of the current frame. The history file is placed in the current working directory (see description of command )cd ). Note that these history database files are not text files (in fact, they are directories themselves), and so are not in human-readable format.
The options to the )history command are as follows:
)change n
will set the number of steps that are saved in memory to n. This option
only has effect when the history data is maintained in a file. If you
have issued )history )memory (or not changed the default) there is no
need to use )history )change.
)on
will start the recording of information. If the workspace is not empty,
you will be asked to confirm this request. If you do so, the workspace
will be cleared and history data will begin being saved. You can also
turn the facility on by issuing )set history on.
)off
will stop the recording of information. The )history )show command will
not work after issuing this command. Note that this command may be issued
to save time, as there is some performance penalty paid for saving the
environment data. You can also turn the facility off by issuing )set
history off.
)file
indicates that history data should be saved in an external file on disk.
)memory
indicates that all history data should be kept in memory rather than
saved in a file. Note that if you are computing with very large objects
it may not be practical to kept this data in memory.
)reset
will flush the internal list of the most recent workspace calculations so
that the data structures may be garbage collected by the underlying Lisp
system. Like )history )change, this option only has real effect when
history data is being saved in a file.
)restore [savedHistoryName]
completely clears the environment and restores it to a saved session, if
possible. The )save option below allows you to save a session to a file
with a given name. If you had issued )history )save jacobi the command
)history )restore jacobi would clear the current workspace and load the
contents of the named saved session. If no saved session name is
specified, the system looks for a file called last.axh.
)save savedHistoryName
is used to save a snapshot of the environment in a file. This file is
placed in the current working directory (see description of command )cd
). Use )history )restore to restore the environment to the state
preserved in the file. This option also creates an input file containing
all the lines of input since you created the workspace frame (for
example, by starting your FriCAS session) or last did a )clear all or
)clear completely.
)show [n] [both]
can show previous input lines and output results. )show will display up
to twenty of the last input lines (fewer if you haven't typed in twenty
lines). )show n will display up to n of the last input lines. )show both
will display up to five of the last input lines and output results. )show
n both will display up to n of the last input lines and output results.
)write historyInputFile
creates an .input file with the input lines typed since the start of the
session/frame or the last )clear all or )clear completely. If
historyInputFileName does not contain a period (``.``) in the filename,
.input is appended to it. For example, )history )write chaos and )history
)write chaos.input both write the input lines to a file called
chaos.input in your current working directory. If you issued one or more
)undo commands, )history )write eliminates all input lines backtracked
over as a result of )undo. You can edit this file and then use )read to
have FriCAS process the contents.
Also See: