16.13 )history
ugSysCmdhistory
history
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 Axiom 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
file:input
Axiom.
Axiom 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.
history )on
set history on
set history off
history )off
Whether the facility is disabled or not,
the value of % in Axiom 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, Axiom will signal an error.
The environment information can either be saved in a file or entirely in
memory (the default).
Each frame
(ugSysCmdframe )
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 ugSysCmdcd ).
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.
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
Common 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 ugSysCmdcd ).
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
Axiom 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 Axiom process
the contents.
Also See:
)frame ugSysCmdframe,
)read ugSysCmdread,
)set ugSysCmdset, and
)undo ugSysCmdundo.