File: asis_ug_6.html

package info (click to toggle)
asis 2008-5
links: PTS
area: main
in suites: squeeze
size: 9,724 kB
ctags: 615
sloc: ada: 95,867; makefile: 259; xml: 19
file content (505 lines) | stat: -rw-r--r-- 22,775 bytes
<HTML>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<!-- Created on May, 22  2008 by texi2html 1.64-gnat-1 -->
<!-- 
Written by: Lionel Cons <Lionel.Cons@cern.ch> (original author)
            Karl Berry  <karl@freefriends.org>
            Olaf Bachmann <obachman@mathematik.uni-kl.de>
            and many others.
Maintained by: Olaf Bachmann <obachman@mathematik.uni-kl.de>
Send bugs and suggestions to <texi2html@mathematik.uni-kl.de>
 
-->
<HEAD>
<TITLE>ASIS-for-GNAT User's Guide: ASIS Interpreter asistant</TITLE>
<META NAME="description" CONTENT="ASIS-for-GNAT User's Guide: ASIS Interpreter asistant">
<META NAME="keywords" CONTENT="ASIS-for-GNAT User's Guide: ASIS Interpreter asistant">
<META NAME="resource-type" CONTENT="document">
<META NAME="distribution" CONTENT="global">
<META NAME="Generator" CONTENT="texi2html 1.64-gnat-1">

</HEAD>

<BODY LANG="" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#800080" ALINK="#FF0000">

<A NAME="SEC38"></A>
<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_5.html#SEC37"> &lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC39"> &gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_7.html#SEC44"> &lt;&lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug.html#SEC_Top"> Up </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_7.html#SEC44"> &gt;&gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug.html#SEC_Top">Top</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_toc.html#SEC_Contents">Contents</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_15.html#SEC56">Index</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_abt.html#SEC_About"> ? </A>]</TD>
</TR></TABLE>
<H1> 5. ASIS Interpreter <CODE>asistant</CODE> </H1>
<!--docid::SEC38::-->
<P>

This chapter describes <CODE>asistant</CODE>, an interactive interface to ASIS queries.
<A NAME="IDX136"></A>
</P><P>

<BLOCKQUOTE><TABLE BORDER=0 CELLSPACING=0> 
<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="asis_ug_6.html#SEC39">5.1 <CODE>asistant</CODE> Introduction</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP"></TD></TR>
<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="asis_ug_6.html#SEC40">5.2 <CODE>asistant</CODE> commands</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP"></TD></TR>
<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="asis_ug_6.html#SEC41">5.3 <CODE>asistant</CODE> variables</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP"></TD></TR>
<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="asis_ug_6.html#SEC42">5.4 Browsing an ASIS tree</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP"></TD></TR>
<TR><TD ALIGN="left" VALIGN="TOP"><A HREF="asis_ug_6.html#SEC43">5.5 Example</A></TD><TD>&nbsp;&nbsp;</TD><TD ALIGN="left" VALIGN="TOP"></TD></TR>
</TABLE></BLOCKQUOTE>
<P>

<A NAME="asistant introduction"></A>
<HR SIZE="6">
<A NAME="SEC39"></A>
<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC38"> &lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC40"> &gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC38"> &lt;&lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC38"> Up </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_7.html#SEC44"> &gt;&gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug.html#SEC_Top">Top</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_toc.html#SEC_Contents">Contents</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_15.html#SEC56">Index</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_abt.html#SEC_About"> ? </A>]</TD>
</TR></TABLE>
<H2> 5.1 <CODE>asistant</CODE> Introduction </H2>
<!--docid::SEC39::-->
<P>

The <CODE>asistant</CODE> tool allows you
to use ASIS without building your own ASIS applications. It
provides a simple command language that allows you to define variables of ASIS
types and to assign them values by calling ASIS queries.
</P><P>

This tool may be very useful while you are learning ASIS:
it lets you try different ASIS queries and see the results immediately.
It does not crash when there is an error in calling an ASIS query
(such as passing an inappropriate <CODE>Element</CODE>); instead <CODE>asistant</CODE> reports an
error and lets you try again.
</P><P>

You can also use <CODE>asistant</CODE> as a debug and "ASIS visualization" tool in
an ASIS application project.  If you have problems
finding out which query should be used in a given situation, or why a given
query does not work correctly with a given piece of Ada code, you may use
<CODE>asistant</CODE> to reconstruct the situation that causes the problems,
and then experiment with ASIS queries.
</P><P>

Though primarily an interactive tool, <CODE>asistant</CODE> also can interpret
sequences of commands written to a file (called a "script file"
<A NAME="IDX137"></A>
below). The <CODE>asistant</CODE> tool can also store in a file the log of an interactive
session that can then be reused as a script file.
</P><P>

The full documentation of <CODE>asistant</CODE> may be found in the
<CITE><CODE>asistant</CODE> Users' Guide</CITE> (file <TT>`asistant.ug'</TT> in the <CODE>asistant</CODE> source directory).
Here is a brief overview of <CODE>asistant</CODE> usage.
</P><P>

The executable for <CODE>asistant</CODE> is created in the <CODE>asistant</CODE>
source directory as a part of the standard procedure of installing
ASIS-for-GNAT as an Ada library (or it is placed in the <TT>`GNATPRO/bin'</TT>
directory when installing ASIS from the binary distribution). Put this
executable somewhere on your path<A NAME="DOCF4" HREF="asis_ug_fot.html#FOOT4">(4)</A>,
and then type
"<CODE>asistant</CODE>" to call <CODE>asistant</CODE> in an interactive mode. As a result,
the program will output brief information about itself and then the
<CODE>asistant</CODE> prompt "<CODE>></CODE>" will appear:
<A NAME="IDX138"></A>
</P><P>

<TABLE><tr><td>&nbsp;</td><td class=smallexample><FONT SIZE=+0><pre>ASIStant - ASIS Tester And iNTerpreter, v1.2
(C) 1997-2002, Free Software Foundation, Inc.
  Asis Version: ASIS 2.0.R

&#62;
</FONT></pre></td></tr></table></P><P>

Now you can input <CODE>asistant</CODE> commands (<CODE>asistant</CODE> supports
in its command language the same form of comments as Ada, and names in
<CODE>asistant</CODE> are not case-sensitive):
</P><P>

<TABLE><tr><td>&nbsp;</td><td class=smallexample><FONT SIZE=+0><pre>&#62;Initialize ("") -- the ASIS Initialize query is called with an
                 -- empty string as a parameter

&#62;set (Cont) --  the non-initialized variable Cont of the ASIS
            --  Context type is created

&#62;Associate (Cont, "", "") --  the ASIS Associate query with two empty
                          --  strings as parameters is called for Cont

&#62;Open (Cont)  --  the ASIS Open query is called for Cont

&#62;set (C_U, Compilation_Unit_Body ("Test", Cont)) -- the variable C_U
  --  of the ASIS Compilation_Unit type is created and initialized as
  --  the result of the call to the ASIS query Compilation_Unit_Body.
  --  As a result, C_U will represent a compilation unit named "Test"
  --  and contained in the ASIS Context named Cont

&#62;set (Unit, Unit_Declaration (C_U))  --  the variable Unit of the ASIS
  --  Element type is created and initialized as the result of calling
  --  the ASIS Unit_Declaration query

&#62;print (Unit) --  as a result of this command, some information about
              --  the current value of Unit will be printed (a user can set
              --  the desired level of detail of this information):

A_PROCEDURE_BODY_DECLARATION at ( 1 : 1 )-( 9 : 9 )

--  suppose now, that we do make an error - we call an ASIS query for
--  an inappropriate element:

&#62;set (Elem, Assignment_Expression (Unit))

--  ASIS will raise an exception, asistant will output the ASIS debug
--  information:

Exception is raised by ASIS query ASSIGNMENT_EXPRESSION.
Status : VALUE_ERROR
Diagnosis :
Inappropriate Element Kind in Asis.Statements.Assignment_Expression

--  it does not change any of the existing variables and it prompts
--  a user again:

&#62; ...
</FONT></pre></td></tr></table></P><P>

<A NAME="asistant commands"></A>
<HR SIZE="6">
<A NAME="SEC40"></A>
<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC39"> &lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC41"> &gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC41"> &lt;&lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC38"> Up </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_7.html#SEC44"> &gt;&gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug.html#SEC_Top">Top</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_toc.html#SEC_Contents">Contents</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_15.html#SEC56">Index</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_abt.html#SEC_About"> ? </A>]</TD>
</TR></TABLE>
<H2> 5.2 <CODE>asistant</CODE> commands </H2>
<!--docid::SEC40::-->
<P>

The list of <CODE>asistant</CODE> commands given in this section is incomplete;
its purpose is only to give a general idea of <CODE>asistant</CODE>'s capabilities.
Standard metalanguage is assumed (i.e., "<CODE>[</CODE><EM>construct</EM><CODE>]</CODE>"
denotes an optional instance of "<EM>construct</EM>").
</P><P>

<DL COMPACT>
<DT><CODE>Help [(name)]</CODE>
<DD><A NAME="IDX139"></A>
Outputs the profile of the ASIS query "<CODE>name</CODE>"; when called with no argument,
 generates general <CODE>asistant</CODE> help information.
<P>

<DT><CODE>Set (name)</CODE>
<DD><A NAME="IDX140"></A>
Creates a (non-initialized) variable "<CODE>name</CODE>" of the ASIS <CODE>Context</CODE> type.
<P>

<DT><CODE>Set (name, expr)</CODE>
<DD>Evaluates the expression "<CODE>expr</CODE>" (it may be any legal <CODE>asistant</CODE>
 expression; a call to some ASIS query is the most common case in practice)
 and creates the variable "<CODE>name</CODE>" of the type and with the value of
"<CODE>expr</CODE>".
<P>

<DT><CODE>Print (expr)</CODE>
<DD><A NAME="IDX141"></A>
Evaluates the expression "<CODE>expr</CODE>" and outputs its value (some information may be
 omitted depending on the level specified by the <CODE>PrintDetail</CODE> command).
<P>

<DT><CODE>Run (<TT>`filename'</TT>)</CODE>
<DD><A NAME="IDX142"></A>
Launches the script from a file <TT>`filename'</TT>, reading further commands from it.
<A NAME="IDX143"></A>
<P>

<DT><CODE>Pause</CODE>
<DD><A NAME="IDX144"></A>
Pauses the current script and turns <CODE>asistant</CODE> into interactive mode.
<P>

<DT><CODE>Run</CODE>
<DD>Resumes a previously <CODE>Pause</CODE>d script.
<P>

<DT><CODE>Browse</CODE>
<DD><A NAME="IDX145"></A>
Switches <CODE>asistant</CODE> into step-by-step ASIS tree browsing.
<P>

<DT><CODE>Log (<TT>`filename'</TT>)</CODE>
<DD><A NAME="IDX146"></A>
Opens the file <TT>`filename'</TT> for session logging.
<P>

<DT><CODE>Log</CODE>
<DD>Closes the current log file.
<P>

<DT><CODE>PrintDetail</CODE>
<DD><A NAME="IDX147"></A>
Toggles whether the <CODE>Print</CODE> command outputs additional information.
<P>

<DT><CODE>Quit [(exit-status)]</CODE>
<DD><A NAME="IDX148"></A>
Quits <CODE>asistant</CODE>.
</DL>
<P>

<A NAME="asistant variables"></A>
<HR SIZE="6">
<A NAME="SEC41"></A>
<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC40"> &lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC42"> &gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC42"> &lt;&lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC38"> Up </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_7.html#SEC44"> &gt;&gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug.html#SEC_Top">Top</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_toc.html#SEC_Contents">Contents</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_15.html#SEC56">Index</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_abt.html#SEC_About"> ? </A>]</TD>
</TR></TABLE>
<H2> 5.3 <CODE>asistant</CODE> variables </H2>
<!--docid::SEC41::-->
<P>

The <CODE>asistant</CODE> tool lets you define variables with Ada-style (simple) names.
Variables can be of
any ASIS type and of conventional <CODE>Integer</CODE>, <CODE>Boolean</CODE> and <CODE>String</CODE> type.
All the variables are created and assigned dynamically by the <CODE>Set</CODE>
command; there are no predefined variables.
</P><P>

There is no type checking in <CODE>asistant</CODE>: each call to a <CODE>Set</CODE>
command may be considered as creating the first argument from scratch and
initializing it by the value provided by the second argument.
</P><P>

<A NAME="Browsing an ASIS tree"></A>
<HR SIZE="6">
<A NAME="SEC42"></A>
<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC41"> &lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC43"> &gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC43"> &lt;&lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC38"> Up </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_7.html#SEC44"> &gt;&gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug.html#SEC_Top">Top</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_toc.html#SEC_Contents">Contents</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_15.html#SEC56">Index</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_abt.html#SEC_About"> ? </A>]</TD>
</TR></TABLE>
<H2> 5.4 Browsing an ASIS tree </H2>
<!--docid::SEC42::-->
<P>

You perform ASIS tree browsing by invoking the <CODE>asistant</CODE> service function
<CODE>Browse</CODE>. This will disable the <CODE>asistant</CODE> command interpreter
and activate the Browser command interpreter. The Browser <CODE>Q</CODE> command
switches back into the <CODE>asistant</CODE> environment by enabling the <CODE>asistant</CODE>
command interpreter and disabling the Browser interpreter.
</P><P>

<CODE>Browse</CODE> has a single parameter of <CODE>Element</CODE> type, which establishes
where the ASIS tree browsing will begin.
<CODE>Browse</CODE> returns a
result of type <CODE>Element</CODE>, namely the <CODE>Element</CODE> at which the tree browsing was
stopped. Thus, if you type:
</P><P>

<TABLE><tr><td>&nbsp;</td><td class=smallexample><FONT SIZE=+0><pre>&#62; set (e0, Browse (e1))
</FONT></pre></td></tr></table></P><P>

you will start ASIS tree browsing from <CODE>e1</CODE>; when you finish
browsing, <CODE>e0</CODE> will represent the last <CODE>Element</CODE> visited during the
browsing.
</P><P>

If you type:
</P><P>

<TABLE><tr><td>&nbsp;</td><td class=smallexample><FONT SIZE=+0><pre>&#62; Browse (e1)
</FONT></pre></td></tr></table></P><P>

you will be able to browse the ASIS tree, but the last <CODE>Element</CODE> of the
browsing will be discarded.
</P><P>

Browser displays the ASIS <CODE>Element</CODE> it currently points at and expects one of
the following commands:
</P><P>

<DL COMPACT>
<DT><CODE>U</CODE>
<DD>Go one step up the ASIS tree (equivalent to calling the ASIS
 <CODE>Enclosing_Element</CODE> query);
<A NAME="IDX149"></A>
<P>

<DT><CODE>D</CODE>
<DD>Go one step down the ASIS tree, to the left-most component of the current <CODE>Element</CODE>
<P>

<DT><CODE>N</CODE>
<DD>Go to the right sibling (to the next <CODE>Element</CODE> in the ASIS tree hierarchy)
<P>

<DT><CODE>P</CODE>
<DD>Go to the left sibling (to the previous <CODE>Element</CODE> in the ASIS tree hierarchy)
<P>

<DT><CODE>\k1k2</CODE>
<DD>where <CODE>k1</CODE> is either <CODE>D</CODE> or <CODE>d</CODE>, and
<CODE>k2</CODE> is either <CODE>T</CODE> or <CODE>t</CODE>.
Change the form of displaying the current <CODE>Element</CODE>: <CODE>D</CODE> turns ON displaying the
debug image, <CODE>d</CODE> turns it OFF. <CODE>T</CODE> turns ON displaying the text image, <CODE>t</CODE>
turns it OFF.
<P>

<DT><CODE>&#60;SPACE&#62;&#60;query&#62;</CODE>
<DD>Call the &#60;query&#62; for the current <CODE>Element</CODE>.
<P>

<DT><CODE>Q</CODE>
<DD>Go back to the <CODE>asistant</CODE> environment; the Browser command interpreter is
disabled and the <CODE>asistant</CODE> command interpreter is enabled with the
current <CODE>Element</CODE> returned as a result of the call to <CODE>Browse</CODE>.
</DL>
<P>

Browser immediately interprets the keystroke and displays the new current
<CODE>Element</CODE>. If the message <CODE>"Cannot go in this direction."</CODE> appears, this
means that traversal in this direction from current node is impossible (that
is, the current node is either a terminal <CODE>Element</CODE> and it is not possible to go
down, or it is the leftmost or the rightmost component of some <CODE>Element</CODE>, and
it is not possible to go left or right, or it is the top <CODE>Element</CODE> in its
enclosing unit structure and it is not possible to go up).
</P><P>

It is possible to issue some ordinary ASIS queries from inside the Browser
(for example, semantic queries). These queries should accept one parameter of
type <CODE>Element</CODE> and return <CODE>Element</CODE> as a result.
</P><P>

When you press <CODE>&#60;SPACE&#62;</CODE>, you are asked to enter the query name. If the
query is legal, the current <CODE>Element</CODE> is replaced by the result of the call to
the given query with the current <CODE>Element</CODE> as a parameter.
</P><P>

<A NAME="Example"></A>
<HR SIZE="6">
<A NAME="SEC43"></A>
<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC42"> &lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_7.html#SEC44"> &gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC38"> &lt;&lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC38"> Up </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_7.html#SEC44"> &gt;&gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug.html#SEC_Top">Top</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_toc.html#SEC_Contents">Contents</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_15.html#SEC56">Index</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_abt.html#SEC_About"> ? </A>]</TD>
</TR></TABLE>
<H2> 5.5 Example </H2>
<!--docid::SEC43::-->
<P>

Suppose we have an ASIS <CODE>Compilation_Unit</CODE> <CODE>Demo</CODE> in the source file <TT>`demo.adb'</TT>:
</P><P>

<TABLE><tr><td>&nbsp;</td><td class=smallexample><FONT SIZE=+0><pre>procedure Demo is
   function F (I : Integer) return Integer;

   function F (I : Integer) return Integer is
   begin
      return (I + 1);
   end F;

   N : Integer;

begin
    N := F (3);
end Demo;
</FONT></pre></td></tr></table></P><P>

Suppose also that the tree for this source is created in the current directory.
Below is a sequence of <CODE>asistant</CODE> commands which does process this
unit. Explanation is provided via <CODE>asistant</CODE> comments.
</P><P>

<TABLE><tr><td>&nbsp;</td><td class=smallexample><FONT SIZE=+0><pre>initialize ("")

--  Create and open a Context comprising all the tree files
--  in the current directory:

Set (Cont)
Associate (Cont, "", "")
Open (Cont)

-- Get a Compilation_Unit (body) named "Demo" from this Context:

Set (CU, Compilation_Unit_Body ("Demo", Cont))

--  Go into the unit structure and get to the expression
--  in the right part of the assignment statements in the unit body:

Set (Unit, Unit_Declaration (CU))
Set (Stmts, Body_Statements (Unit, False))
Set (Stmt, Stmts (1))
Set (Expr, Assignment_Expression (Stmt))

-- Output the debug image and the text image of this expression:

Print (Expr)
Print (Element_Image (Expr))

--  This expression is of A_Function_Call kind, so it's possible to ask
--  for the declaration of the called function:

Set (Corr_Called_Fun, Corresponding_Called_Function (Expr))

--  Print the debug and the text image of the declaration of the called
--  function:

Print (Corr_Called_Fun)
Print (Element_Image (Corr_Called_Fun))

-- Close the asistant session:

Quit
</FONT></pre></td></tr></table></P><P>

<A NAME="ASIS Application Templates"></A>
<HR SIZE="6">
<TABLE CELLPADDING=1 CELLSPACING=1 BORDER=0>
<TR><TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_6.html#SEC38"> &lt;&lt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_7.html#SEC44"> &gt;&gt; </A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT"> &nbsp; <TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug.html#SEC_Top">Top</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_toc.html#SEC_Contents">Contents</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_15.html#SEC56">Index</A>]</TD>
<TD VALIGN="MIDDLE" ALIGN="LEFT">[<A HREF="asis_ug_abt.html#SEC_About"> ? </A>]</TD>
</TR></TABLE>
<BR>  
<FONT SIZE="-1">
This document was generated
by <I>Mail Server</I> on <I>May, 22  2008</I>
using <A HREF="http://www.mathematik.uni-kl.de/~obachman/Texi2html/"><I>texi2html</I></A>

</BODY>
</HTML>