DefaultDirectory , PrettyPrinter , Help , HistorySize .

# Startup configuration

Yacas allows you to configure a few things at startup. The file `~/.yacasrc` is written in the Yacas language and will be executed when Yacas is run. The following functions can be useful in the `~/.yacasrc` file.

DefaultDirectory | add directory to path for Yacas scripts
PrettyPrinter | set routine to use as pretty-printer
Help | get documentation for some command
HistorySize | set size of history file

###

DefaultDirectory -- add directory to path for Yacas scripts

##### Internal function

##### Calling format:

    DefaultDirectory(path)

##### Parameters:

`path` -- a string containing a full path where yacas script files reside

##### Description:

When loading files, yacas is also allowed to look in the folder "path". `path` will be prepended to the file name before trying to load the file. This means that "path" should end with a forward slash (under Unix-like operating systems).

Yacas first tries to load a file from the current directory, and otherwise it tries to load from directories defined with this function, in the order they are defined. Note there will be at least one directory specified at start-up time, defined during compilation. This is the directory Yacas searches for the initialization scripts and standard scripts.

##### Examples:

    In> DefaultDirectory("/home/user/myscripts/");
    Out> True;

##### See also:

Load , Use , DefLoad , FindFile .

###

PrettyPrinter -- set routine to use as pretty-printer

##### Standard library

##### Calling format:

    PrettyPrinter(printer)

##### Parameters:

printer - a string containing the name of a function that can pretty-print an expression

##### Description:

This function sets up the function printer to print out the results on the command line. This can be reset to the internal printer with `PrettyPrinter()`.

##### Examples:

    In> Taylor(x,0,5)Sin(x)
    Out> x-x^3/6+x^5/120;
    In> PrettyPrinter("PrettyForm");

    True

    Out>
    In> Taylor(x,0,5)Sin(x)

         3    5
        x    x
    x - -- + ---
        6    120

    Out>
    In> PrettyPrinter();
    Out> True;
    In> Taylor(x,0,5)Sin(x)
    Out> x-x^3/6+x^5/120;

##### See also:

PrettyForm , Write .

###

Help -- get documentation for some command

##### Standard library

##### Calling format:

    Help()
    Help(function)

##### Parameters:

function - a string containing the name of a function to show help for

##### Description:

When help is requested by the user, by typing `?`function or `??`, the functions `Help()` (for `??`) and `Help(`function`)` (for `?`function) are called. By default, `lynx` is used as a browser (another recommended text-only browser is `links`). The help resides in the subdirectory `documentation/` under the directory the math scripts were installed in. So the help files can be found using `FindFile`.

The function `Help` is auxiliary and should not be used to actually get online help.

##### Examples:

To use netscape for browsing help, enter the following commands:

    Help(_f) <-- SystemCall("netscape " :
      FindFile("documentation/ref.html"):"#":f);
    Help() := SystemCall("netscape " :
      FindFile("documentation/books.html"));

##### See also:

SystemCall , FindFile .

###

HistorySize -- set size of history file

##### Internal function

##### Calling format:

    HistorySize(n)

##### Parameters:

`n` -- number of lines to store in history file

##### Description:

When exiting, yacas saves the command line history to a file `~/.yacas_history`. By default it will only save the last 50 lines, to save space on the hard disk. This can be overridden with this function. Passing -1 tells the system to save all lines.

##### Examples:

    In> HistorySize(200)
    Out> True;
    In> quit