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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE book [
<!ENTITY % eclent SYSTEM "ecl.ent">
%eclent;
]>
<book xmlns="http://docbook.org/ns/docbook" version="5.0" xml:lang="en">
<chapter xml:id="Program-development">
 <title>Program Development Facilities</title>

<section xml:id="The-stepper">
<title>The Stepper</title>
<blockquote>
<screen><indexterm role="fn"><primary>step</primary></indexterm>&#151; Macro: <function>step</function> <varname>form</varname></screen>
<para>Starts evaluating the <replaceable>form</replaceable> in the single-step mode.  In this mode, before
any form is evaluated, the Stepper will print the form and prompt the user for
a Stepper command.  The Stepper binds the two variables print-level
and print-length both to <literal>2</literal>, so that the current form may not
occupy too much space on the screen.  A Stepper command will be executed when
the user types the single character for the command followed by the required
arguments, if any, and presses the newline key.  If the user presses the
newline key without having typed any character, then the Stepper will assume
that the Stepper command <literal>n</literal> was abbreviated.</para>
</blockquote>
<para>The stepper commands are:</para>
<variablelist>
<varlistentry>
<term><literal>Newline</literal></term>
<listitem>
<para>Next.  Evaluates the current form in the single-step mode.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>:s</replaceable>, <replaceable>:skip</replaceable></term>
<listitem>
<para>Skip.  Evaluates the current form in the ordinary mode.  The single-step mode
will be resumed at completion of the evaluation.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>:b</replaceable>, <replaceable>:back</replaceable></term>
<listitem>
<para>Backwards.  Steps back to previous step form.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>:pr</replaceable>, <replaceable>:print</replaceable></term>
<listitem>
<para>Print.  Pretty-prints the current form.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>:form</replaceable></term>
<listitem>
<para>Form. Return the current form.  Nothing is done, but the current form is
returned as the value of this command.  As a consequence, it is printed by the
top level in the usual way and saved in the variable <literal>*</literal>.  The main
purpose of this command is to allow the current form to be examined further by
accessing <literal>*</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>:ret</replaceable>, <replaceable>:return</replaceable></term>
<listitem>
<para>Return. Return without evaluating the current form.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>:x</replaceable>, <replaceable>:exit</replaceable></term>
<listitem>
<para>Exit.  Evaluates the current form and any other forms in the ordinary mode.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>?</literal></term>
<listitem>
<para>Help. Lists the commands.</para>
</listitem>
</varlistentry>
</variablelist>
</section>

<section xml:id="Errors">
<title>Errors</title>
<blockquote>
<screen><indexterm role="vr"><primary>*break-enable*</primary></indexterm>&#151; Variable: <varname>*break-enable*</varname></screen>
<para>This variable is used to determine whether to enter the break loop (see Section
5.4) when an error occurs.  Even the function <literal>break</literal> checks this
variable.  Initially, this variable is set to <replaceable>T</replaceable>, and thus an error will
invoke the break loop.  If the value is (), functions that cause fatal
errors, such as <literal> error</literal>, will just print an error message and control
will return to the top-level loop (or to the current break loop, if already in
the break loop).  Functions that cause correctable errors, such as <literal>
cerror</literal>, will print an error message and a &ldquo;continue message&rdquo;, and control
will return to the next form.  In &ECL;, backtrace is not part of an error
message, but a break loop command will print backtrace.  Therefore, if
break-enable is (), no backtrace appears on the screen.</para>
<para>When the break loop is entered, break-enable will be bound to
().</para>
</blockquote>
</section>

<section xml:id="The-break-loop">
<title>The Break Loop</title>
<para>The break loop is a read-eval-print loop similar to the top-level loop.  In
addition to ordinary Lisp forms, the break loop accepts various commands with
which the user can inspect and modify the state of the program execution.  Each
break loop command is identified with a keyword (i.e., a symbol in the
<literal>keyword</literal> package).  A break loop command is executed when the user inputs
a list whose first element is the keyword that identifies the command.  The
rest of the list is the arguments to the command.  They are evaluated before
being passed to the command.  If the command needs no arguments, then the user
may input only the keyword.  It is an error if the given keyword does not
identify any command.  Any other input to the break loop is regarded as an
ordinary Lisp form; the form will be evaluated and the resulting values will be
printed on the terminal.</para>
<para>There can be several instances of the break loop at the same time, and each
such instance is identified by a <emphasis>level number</emphasis>.  When the break loop is
entered during execution in the top-level loop, the break loop instance is
given the level number 1.  The break loop instance that is entered from the
level <emphasis>n</emphasis> break loop is given the level number <replaceable>n</replaceable><literal>+1</literal>.  The
prompt of the level <emphasis>n</emphasis> break loop is <replaceable>n</replaceable><literal>+1</literal> consecutive
<literal>&gt;</literal>'s, occasionally prefixed with the name of the current package.</para>
<para>The break loop keeps track of the invocation sequence of functions (including
special forms and macro expansion functions), which led up to the break loop
from the previous break loop (or from the top-level loop, if the current break
loop is level 1).  The invocation sequence is maintained in a pushdown stack of
<emphasis>events</emphasis>.  An event consists of an <emphasis>event function</emphasis> and an
<emphasis>event environment</emphasis>.  An event function is:</para>
<orderedlist numeration="arabic">
<listitem>
<para>an interpreted (i.e., not compiled) function (global function, local function, lambda-expression, or closure),</para>
</listitem>
<listitem>
<para>a special form within an interpreted function,</para>
</listitem>
<listitem>
<para>a macro expansion function called from an interpreted function,</para>
</listitem>
<listitem>
<para>a compiled function called from an interpreted function, or</para>
</listitem>
<listitem>
<para>a compiled function called from another compiled function which
was compiled while the <literal>safety</literal> optimize level is 3 or with a
<literal>notinline</literal> declaration for the called function (see Chapter 7).</para>
</listitem>
</orderedlist>
<para>An event is pushed on the event stack when execution of its event function
begins, and is popped away at the completion of the execution.  An event
environment is the `environment' of the event function at the time the next
event is pushed.  Actually, an event environment is a pointer to the main stack
of &ECL;.  For each interpreted event function (i.e., event function in
classes 1, 2, and 3), the pointer points to the first entry of the three
contiguous main stack entries that hold the lexical environment of the event
function.  For each compiled event function (i.e., event function in classes 4
and 5), the pointer is set to the first entry of the main stack area that is
used locally by the compiled code.  In most cases, the first argument to the
compiled function is saved in the first entry, the second argument in the
second entry, and so on.  The local variables of the function are allocated in
the entries following the arguments.  However, this is not always the case.
Refer to Section 7.3 for variable allocations in compiled functions.</para>
<para>By break level commands, the user can choose one of the events as the
<emphasis>current event</emphasis>.  If the current event function is an interpreted event
function, then the break loop evaluates Lisp forms in the lexical environment
retrieved from the event environment.  In particular, local variables may be
referenced by the variable names, local functions and local macros may be
invoked as usual, established blocks may be exited from, and tags may be used
as the destination of <literal>go</literal>.  If the current function is a compiled
function, Lisp forms are evaluated in the null environment.</para>
<para>Within the break loop, each event is represented by the <emphasis>event symbol</emphasis>.
The <replaceable>:backtrace</replaceable> command, for example, lists events in terms of their event
symbols.  If the event function is a named function (global or local) or a
macro expansion function, then the function or macro name is used as the event
symbol.  If the event function is a special form, then the name of the special
form is used.  If the event function is a lambda-expression (or a closure),
then the symbol lambda (or lambda-closure) is used.</para>
<para>To suppress unnecessary information, the user can hide (or make invisible) some
of the events.  Invisible events do not appear in the backtrace, for example.
Initially, only those events are invisible whose event symbols belong to the
system internal package system.  When the break loop is entered, the last
visible event becomes the current event.</para>
<para>The break loop commands are described below.  Some of the commands allow
abbreviation in the keywords that identify them.  For example, the user may
abbreviate <replaceable>:current</replaceable> as <replaceable>:c</replaceable>.  The break loop commands return no values
at all.</para>
<blockquote>
<screen><indexterm role="fn"><primary>:current</primary></indexterm>&#151; Break Command: <function>:current</function></screen>
<screen><indexterm role="fn"><primary>:c</primary></indexterm>&#151; Break Command: <function>:c</function> <varname></varname></screen>
<para>Prints the event symbol of the current event.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:previous</primary></indexterm>&#151; Break Command: <function>:previous</function> <varname>&amp;optional</varname> <varname>n</varname></screen>
<screen><indexterm role="fn"><primary>:p</primary></indexterm>&#151; Break Command: <function>:p</function> <varname>&amp;optional n</varname></screen>
<para>Makes the <replaceable>n</replaceable>-th previous visible event the
new current event.  Invisible events are not counted.  If there are
less than <replaceable>n</replaceable> previous events, then the first visible event in the
invocation sequence becomes the new current event. <replaceable>n</replaceable> must be a
positive integer and the default is <literal>1</literal>.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:next</primary></indexterm>&#151; Break Command: <function>:next</function> <varname>&amp;optional</varname> <varname>n</varname></screen>
<screen><indexterm role="fn"><primary>:n</primary></indexterm>&#151; Break Command: <function>:n</function> <varname>&amp;optional n</varname></screen>
<para>Makes the <replaceable>n</replaceable>-th next visible event the
new current event.  If there are less than <replaceable>n</replaceable> next events,
then the last visible event in the invocation sequence
becomes the new current event. <replaceable>n</replaceable>  must be a positive integer and the
default is <literal>1</literal>.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:backtrace</primary></indexterm>&#151; Break Command: <function>:backtrace</function></screen>
<screen><indexterm role="fn"><primary>:b</primary></indexterm>&#151; Break Command: <function>:b</function> <varname></varname></screen>
<para>Prints the event symbols of all visible events in order.  The symbol of
the current event is printed
in upper-case letters and the event symbols of other events are in lower-case.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:help</primary></indexterm>&#151; Break Command: <function>:help</function></screen>
<screen><indexterm role="fn"><primary>:h</primary></indexterm>&#151; Break Command: <function>:h</function> <varname></varname></screen>
<para>Lists the break loop commands.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:quit</primary></indexterm>&#151; Break Command: <function>:quit</function> <varname>&amp;optional</varname> <varname>n</varname></screen>
<screen><indexterm role="fn"><primary>:q</primary></indexterm>&#151; Break Command: <function>:q</function> <varname>&amp;optional n</varname></screen>
<para>Returns control to the level <replaceable>n</replaceable> break loop.  If <replaceable>n</replaceable> is 0 or if <replaceable>n</replaceable>
is omitted, then control will return to the top-level loop. <replaceable>n</replaceable> must be a
non-negative integer smaller than the current break level.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:continue</primary></indexterm>&#151; Break Command: <function>:continue</function></screen>
<screen><indexterm role="fn"><primary>:c</primary></indexterm>&#151; Break Command: <function>:c</function> <varname></varname></screen>
<para>Returns control to the caller of the break loop.  If the break loop has been
entered from <literal>cerror</literal>, <literal>cerror</literal> returns () as its value and
control will resume at that point.  Otherwise, this command returns control to
the previous break loop (or to the top-level loop, if the current break level
is <literal>1</literal>).</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:variables</primary></indexterm>&#151; Break Command: <function>:variables</function></screen>
<screen><indexterm role="fn"><primary>:v</primary></indexterm>&#151; Break Command: <function>:v</function> <varname></varname></screen>
<para>Prints the names of the bound variables in the current
environment.  To see the value of a bound variable, just type the
variable name.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:functions</primary></indexterm>&#151; Break Command: <function>:functions</function></screen>
<para>Prints the names of the local functions and local macros in the current
environment.  To see the definition of a local function or macro, use the
function special form in the usual way.  That is, <literal>(function <replaceable>name</replaceable>)</literal>
will return the definition of the local function or macro whose name is
<replaceable>name</replaceable>.  Local functions and local macros may be invoked as usual.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:blocks</primary></indexterm>&#151; Break Command: <function>:blocks</function></screen>
<para>Prints the names of the blocks established in the current environment.  If a
block <replaceable>block</replaceable> is established, then the <literal>return-from</literal> form
<literal>(return-from <replaceable>block value</replaceable>)</literal> works as usual.  That is, the block form
that established <replaceable>block</replaceable> will return <replaceable>value</replaceable> as its value and control
will resume at that point.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:tags</primary></indexterm>&#151; Break Command: <function>:tags</function></screen>
<para>Prints the tags established in the current environment.  If a tag <replaceable>tag</replaceable> is
established, then the <literal>go</literal> form <literal>(go <replaceable>tag</replaceable>)</literal> works as usual.
That is, control will resume at the position of <replaceable>tag</replaceable> in the surrounding
<literal>tagbody</literal>.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:local</primary></indexterm>&#151; Break Command: <function>:local</function> <varname>&amp;optional</varname> <varname>n</varname></screen>
<screen><indexterm role="fn"><primary>:l</primary></indexterm>&#151; Break Command: <function>:l</function> <varname>&amp;optional n</varname></screen>
<para>If <replaceable>n</replaceable> is <literal>0</literal> or if it is omitted, then this command prints the value
stored in the main stack entry that is pointed to by the current event
environment. <replaceable>n</replaceable> is an offset from that entry.  If <replaceable>n</replaceable> is positive,
then the value of the <emphasis>n</emphasis>-th next (i.e., toward the top of the main stack)
entry is printed.  If <replaceable>n</replaceable> is negative, then the value of the <replaceable>n</replaceable>-th
previous (i.e., toward the bottom of the main stack) entry is printed. <replaceable>n</replaceable>
must be an integer.  It is an error if the specified entry does not lie between
the bottom and the top of the stack.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:hide</primary></indexterm>&#151; Break Command: <function>:hide</function> <varname>symbol</varname></screen>
<para>Hides all events whose event symbol is <replaceable>symbol</replaceable>.  In particular, by
<literal>:hide 'lambda</literal> and <literal>hide 'lambda-closure</literal>, all events become
invisible whose event functions are lambda-expressions and closures,
respectively.  If the event symbol of the current event happens to be
<replaceable>symbol</replaceable>, then the last previous visible event will become the new current
event.  <replaceable>symbol</replaceable> must be a symbol.</para>
<para>Events of <literal>eval</literal> and <literal>evalhook</literal> may never become invisible and
attempts to hide them are simply ignored.  It is always the case that the first
event function is either <literal>eval</literal> or <literal>evalhook</literal>.  Keeping both of them
visible is the simplest way to avoid the silly attempts of the user to hide all
events.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:hide-package</primary></indexterm>&#151; Break Command: <function>:hide-package</function> <varname>package</varname></screen>
<para>Hides all events whose event symbol belongs to the package
<replaceable>package</replaceable>. <replaceable>package</replaceable> may be any object that represents a package, i.e.,
a package object, a symbol, or a string.  If the event symbol of the current
event happens to belong to the package <replaceable>package</replaceable>, then the last previous
visible event will become the new current event.  Even if <literal>lisp</literal> package
was specified as <replaceable>package</replaceable>, events of <literal>eval</literal> and <literal>evalhook</literal> do
not become invisible.  See the description of <replaceable>:hide</replaceable> above.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:unhide</primary></indexterm>&#151; Break Command: <function>:unhide</function> <varname>symbol</varname></screen>
<para><replaceable>:unhide</replaceable> is the inverse command of <replaceable>:hide</replaceable>.  If, however, <replaceable> symbol</replaceable>
belongs to one of the <replaceable>:hide-package</replaceable>d packages, events of <replaceable>symbol</replaceable>
become visible only after the package is <literal>:unhide-package
'd</literal>. <replaceable>symbol</replaceable> must be a symbol.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>:unhide-package</primary></indexterm>&#151; Break Command: <function>:unhide-package</function> <varname>package</varname></screen>
<para><replaceable>:unhide-package</replaceable> is the inverse command of <replaceable>:hide-package</replaceable>.  However, an
event whose event symbol belongs to <replaceable>package</replaceable> becomes visible only after
the symbol is <literal>unhide 'd</literal>, if the symbol was <replaceable>:code 'd</replaceable>
before. <replaceable>package</replaceable> may be any object that represents a package, i.e., a
package object, a symbol, or a string.</para>
</blockquote>
<para>Example:</para>
<para><screen>
&gt; (defun fact (x) (if (= x 0) one (* x (fact (1- x)))))
fact                    ;;;  Wrong definition for  fact, the factorial.

&gt; (fact 6)              ;;;  Tries to calculate factorial 6.

Error: The variable ONE is unbound.
Error signalled by IF.

Broken at IF:           ;;;  Enters the break-loop.
&gt;&gt; :h                   ;;;  Help.

Break commands:
:q(uit)         Return to some previous break level.
:pop            Pop to previous break level.
:c(ontinue)     Continue execution.
:b(acktrace)    Print backtrace.
:f(unction)     Show current function.
:p(revious)     Go to previous function.
:n(ext)         Go to next function.
:g(o)           Go to next function.
:fs             Search forward for function.
:bs             Search backward for function.
:v(ariables)    Show local variables, functions, blocks, and tags.
:l(ocal)        Return the nth local value on the stack.
:hide           Hide function.
:unhide         Unhide function.
:hp             Hide package.
:unhp           Unhide package.
:unhide-all     Unhide all variables and packages.
:vs             Show value stack.
:bds            Show binding stack.
:m(essage)      Show error message.
:hs             Help stack.

Top level commands:
:cf             Compile file.
:exit or ^D     Exit Lisp.
:ld             Load file.
:step           Single step form.
:tr(ace)        Trace function.
:untr(ace)      Untrace function.

Help commands:
:apropos        Apropos.
:doc(ument)     Document.
:h(elp) or ?    Help.  Type ":help help" for more information.

&gt;&gt; :b                   ;;;  Backtrace.
Backtrace: eval &gt; fact &gt; if &gt; fact &gt; if &gt; fact &gt; if &gt; fact &gt;
if &gt; fact &gt; if &gt; fact &gt; if &gt; fact &gt; IF

&gt;&gt;: p                   ;;;  Moves to the previous event.
Broken at FACT.

&gt;&gt; :b                   ;;;  Now inside of  fact  but outside of  if.
Backtrace: eval &gt; fact &gt; if &gt; fact &gt; if &gt; fact &gt; if &gt; fact &gt;
if &gt; fact &gt; if &gt; fact &gt; if &gt; FACT &gt; if

&gt;&gt; :v                   ;;;  Shows local variables.
Local variables:
X: 1
Block names: FACT.

&gt;&gt; x                    ;;;  The value of x is 1.
1

&gt;&gt; (return-from fact 1) ;;;  Returns from the  fact  block with value  1.
720                     ;;;  Now the correct answer.

&gt;                      ;;;  Top-level.
</screen></para>
</section>

<section xml:id="Describe-and-inspect">
<title>Describe and Inspect</title>
<blockquote>
<screen><indexterm role="fn"><primary>describe</primary></indexterm>&#151; Function: <function>describe</function> <varname>object</varname></screen>
<para>Prints the information about <replaceable>object</replaceable> to the stream that is the value of
<literal>*standard-output*</literal>.  The description of an object consists of several
fields, each of which is described in a recursive manner.  For example, a
symbol may have fields such as home package, variable documentation, value,
function documentation, function binding, type documentation, <literal>deftype</literal>
definition, properties.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>inspect</primary></indexterm>&#151; Function: <function>inspect</function> <varname>object</varname></screen>
<para>Prints the information about <replaceable>object</replaceable> in an interactive manner.  The output
of inspect is similar to that of <literal>describe</literal>, but after printing the label
and the value of a field (the value itself is not <literal>describe 'd</literal>), it
prompts the user to input a one-character command.  The input to <literal>inspect</literal>
is taken from the stream that is the value of <literal>*query-io*</literal>.  Normally, the
inspection of <replaceable>object</replaceable> terminates after all of its fields have been
inspected.  The following commands are supported:</para>
<variablelist>
<varlistentry>
<term><literal>n</literal></term>
<listitem>
<para>Next. Goes to the next level; the field is inspected recursively.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>s</literal></term>
<listitem>
<para>Skip. Skips the inspection of the field. <literal>inspect</literal> proceeds to the next
field.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>p</literal></term>
<listitem>
<para>Print. Pretty-prints the field and prompts again.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>u</literal> <replaceable>form</replaceable></term>
<listitem>
<para>Update. The <replaceable>form</replaceable> is evaluated and the field is replaced by the resulting
value.  If the field cannot be updated, the message <literal>Not updated.</literal>  will
be printed.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>a</literal></term>
<listitem>
<para>Abort. Aborts the inspection of the current object.  The field and
the rest of the fields are not inspected.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>e</literal> <replaceable>form</replaceable></term>
<listitem>
<para>Eval. Evaluates the specified form in the null environment and prints the
resulting values.  Then prompts again with the same field.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>q</literal></term>
<listitem>
<para>Quit. Aborts the entire inspection.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>?</literal></term>
<listitem>
<para>Help. Lists the <literal>inspect</literal> commands.</para>
</listitem>
</varlistentry>
</variablelist>
</blockquote>
</section>

<section xml:id="The-profiler">
<title>The Profiler</title>
<para>The profiler tool is enabled by default in the basic &ECL; configuration.  It
can be disabled with the <literal>configure</literal> option <literal>--disable-profiler</literal>.</para>
<blockquote>
<screen><indexterm role="fn"><primary>profile</primary></indexterm>&#151; sys: <function>profile</function> <varname>grain</varname> <varname>&amp;optional</varname> <varname>address</varname></screen>
<para>This function activates the profiling of subsequent executions.  <replaceable>grain</replaceable> is
a value between 1 and 16384 which indicates the granularity of code segments to
consider. There is a counter for each such segment.  With each clock tick, the
current segment is identified and its corresponding histogram count is
incremented.  A value of 0 for <replaceable>grain</replaceable> means stop profiling.  <replaceable>address</replaceable>
indicates the base address for the code being profiled.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>display-profile</primary></indexterm>&#151; sys: <function>display-profile</function></screen>
<para>Displays the histogram of accumulated tick counts.  The ticks are attributed to
the compiled Lisp function whose base address is closest to the start of the
segment.  This may not be totally accurate for system functions which invoke
some auxiliary function to do the job.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>clear-profile</primary></indexterm>&#151; sys: <function>clear-profile</function></screen>
<para>Clears the profile histogram.</para>
</blockquote>
<blockquote>
<screen><indexterm role="vr"><primary>sys</primary></indexterm>&#151; Variable: <varname>sys</varname> <type>*profile-array*</type></screen>
<para>Contains the profile histogram: two short integer counters are packed in each
value of this array of fixnums.</para>
</blockquote>
</section>

<section xml:id="Online-help">
<title>Online Help</title>
<para>Online help is provided by the following functions.</para>
<blockquote>
<screen><indexterm role="fn"><primary>help</primary></indexterm>&#151; Function: <function>help</function> <varname>&amp;optional symbol</varname></screen>
<para><literal>help</literal> with no arguments prints a greeting message to &ECL; beginners.
<literal>help</literal> with a symbol argument prints the documentation associated
with the symbol.</para>
</blockquote>
<blockquote>
<screen><indexterm role="fn"><primary>help*</primary></indexterm>&#151; Function: <function>help*</function> <varname>string &amp;optional package</varname></screen>
<para>Prints the documentation associated with those symbols in the specified
<replaceable>package</replaceable> whose print names contain <replaceable>string</replaceable> as substring.
<replaceable>string</replaceable> may be a symbol, in which case the print name of that symbol is
used. <replaceable>package</replaceable> is optional and defaults to the LISP package.
If <replaceable>package</replaceable> is (), then all packages are searched.</para>
</blockquote>
</section>
</chapter>
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