Info Catalog calc: Recalling Variables calc: Store and Recall calc: Let Command

calc: Operations on Variables

 
 13.3 Other Operations on Variables
 ==================================
 
 The ‘s e’ (‘calc-edit-variable’) command edits the stored value of a
 variable without ever putting that value on the stack or simplifying or
 evaluating the value.  It prompts for the name of the variable to edit.
 If the variable has no stored value, the editing buffer will start out
 empty.  If the editing buffer is empty when you press ‘C-c C-c’ to
 finish, the variable will be made void.  Editing Stack Entries,
 for a general description of editing.
 
    The ‘s e’ command is especially useful for creating and editing
 rewrite rules which are stored in variables.  Sometimes these rules
 contain formulas which must not be evaluated until the rules are
 actually used.  (For example, they may refer to ‘deriv(x,y)’, where ‘x’
 will someday become some expression involving ‘y’; if you let Calc
 evaluate the rule while you are defining it, Calc will replace
 ‘deriv(x,y)’ with 0 because the formula ‘x’ does not itself refer to
 ‘y’.)  By contrast, recalling the variable, editing with ‘`’, and
 storing will evaluate the variable’s value as a side effect of putting
 the value on the stack.
 
    There are several special-purpose variable-editing commands that use
 the ‘s’ prefix followed by a shifted letter:
 
 ‘s A’
      Edit ‘AlgSimpRules’.  Algebraic Simplifications.
 ‘s D’
      Edit ‘Decls’.  Declarations.
 ‘s E’
      Edit ‘EvalRules’.  Basic Simplifications.
 ‘s F’
      Edit ‘FitRules’.  Curve Fitting.
 ‘s G’
      Edit ‘GenCount’.  Solving Equations.
 ‘s H’
      Edit ‘Holidays’.  Business Days.
 ‘s I’
      Edit ‘IntegLimit’.  Calculus.
 ‘s L’
      Edit ‘LineStyles’.  Graphics.
 ‘s P’
      Edit ‘PointStyles’.  Graphics.
 ‘s R’
      Edit ‘PlotRejects’.  Graphics.
 ‘s T’
      Edit ‘TimeZone’.  Time Zones.
 ‘s U’
      Edit ‘Units’.  User-Defined Units.
 ‘s X’
      Edit ‘ExtSimpRules’.  Unsafe Simplifications.
 
    These commands are just versions of ‘s e’ that use fixed variable
 names rather than prompting for the variable name.
 
    The ‘s p’ (‘calc-permanent-variable’) command saves a variable’s
 value permanently in your Calc init file (the file given by the variable
 ‘calc-settings-file’, typically ‘~/.emacs.d/calc.el’), so that its value
 will still be available in future Emacs sessions.  You can re-execute
 ‘s p’ later on to update the saved value, but the only way to remove a
 saved variable is to edit your calc init file by hand.  (General
 Mode Commands, for a way to tell Calc to use a different file for the
 Calc init file.)
 
    If you do not specify the name of a variable to save (i.e., ‘s p
 <RET>’), all Calc variables with defined values are saved except for the
 special constants ‘pi’, ‘e’, ‘i’, ‘phi’, and ‘gamma’; the variables
 ‘TimeZone’ and ‘PlotRejects’; ‘FitRules’, ‘DistribRules’, and other
 built-in rewrite rules; and ‘PlotDataN’ variables generated by the
 graphics commands.  (You can still save these variables by explicitly
 naming them in an ‘s p’ command.)
 
    The ‘s i’ (‘calc-insert-variables’) command writes the values of all
 Calc variables into a specified buffer.  The variables are written with
 the prefix ‘var-’ in the form of Lisp ‘setq’ commands which store the
 values in string form.  You can place these commands in your Calc init
 file (or ‘.emacs’) if you wish, though in this case it would be easier
 to use ‘s p <RET>’.  (Note that ‘s i’ omits the same set of variables as
 ‘s p <RET>’; the difference is that ‘s i’ will store the variables in
 any buffer, and it also stores in a more human-readable format.)
 

Info Catalog calc: Recalling Variables calc: Store and Recall calc: Let Command