use
==============================================

Purpose
----------------

Loads a compiled file at the beginning of the compilation of a source program.

.. _use:
.. index:: use

Format
----------------

::

    use fname;

**Parameters**

    :fname: (*literal or ^string*), the name of a compiled file created using the `compile` or the `saveall` command.

Remarks
-------

The `use` command can be used ONCE at the TOP of a program to load in a
compiled file which the rest of the program will be added to. In other
words, if *xy.e* had the following lines:

::

   library pgraph;
   external proc xy;
   x = seqa(0.1,0.1,100);

it could be compiled to :file:`xy.gcg`. Then the following program could be run:

::

   use xy;
   xy(x, sin(x));

which would be equivalent to:

::

   new;
   library pgraph;
   x = seqa(0.1,0.1,100);
   xy(x, sin(x));

The `use` command can be used at the top of files that are to be compiled
with the `compile` command. This can greatly shorten compile time for a
set of closely related programs. For example:

::

   library pgraph;
   external proc xy,logx,logy,loglog,hist;
   saveall pgraph;

This would create a file called :file:`pgraph.gcg` containing all the
procedures, strings and matrices needed to run PQG programs. Other
programs could be compiled very quickly with the following statement at
the top of each:

::

   use pgraph;

or the same statement could be executed once, for instance from the
command prompt, to instantly load all the procedures for PQG.

When the compiled file is loaded with `use`, all previous symbols and
procedures are deleted before the program is loaded. It is therefore
unnecessary to execute a `new` before `use`'ing a compiled file.

`use` can appear only ONCE at the TOP of a program.

.. seealso:: Functions `compile`, `run`, `saveall`