<?xml version="1.0" encoding="UTF-8"?>
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<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="http://www.w3.org/2000/svg" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:db="http://docbook.org/ns/docbook" xmlns:scilab="http://www.scilab.org" xml:lang="en" xml:id="while">
    <refnamediv>
        <refname>while</refname>
        <refpurpose>Opens a block of instructions iterated on a heading condition</refpurpose>
    </refnamediv>
    <refsection>
        <title>Description</title>
        <para>
            The <literal>while</literal> clause must be terminated by
            <literal>"end"</literal>.
        </para>
        <para>
            <literal>while expr ,instructions,..., end</literal>
        </para>
        <para>
            <literal>while expr do instructions,..., end</literal>
        </para>
        <para>
            <literal>while expr then instructions,..., end</literal>
        </para>
        <para>Notes:</para>
        <itemizedlist>
            <listitem>
                <para>
                    The only constraint is that each <literal>then</literal> or
                    <literal>do</literal> keyword must be on the same line as
                    <literal>while</literal> keyword.
                </para>
            </listitem>
            <listitem>
                <para>
                    Keywords <literal>then</literal> or <literal>do</literal> can
                    be replaced by a carriage return or a comma. For compatibility
                    with Matlab it is also possible, but not recommended, to put a
                    space between the end of the expression and the beginning of
                    the first instruction.
                </para>
            </listitem>
        </itemizedlist>
        <para>
            According to the Code Conventions for the Scilab Programming Language it is recommended:
        </para>
        <itemizedlist>
            <listitem>
                <para>
                    Start each statement on a new line.
                </para>
            </listitem>
            <listitem>
                <para>
                    Write no more than one simple statement per line.
                </para>
            </listitem>
            <listitem>
                <para>
                    Break compound statements over multiple lines.
                </para>
            </listitem>
        </itemizedlist>
        <para>
            For example, use:
        </para>
        <programlisting role=""><![CDATA[
i = 0;
while i<5
    disp(i);
    i = i + 1;
end
]]></programlisting>
        <para>
            rather than
        </para>
        <programlisting role=""><![CDATA[
i = 0; while i<5, disp(i), i = i + 1; end
]]></programlisting>
        <warning>
          The number of characters used to define the body of any conditional instruction
          (if while for or select/case) must be limited to 16k.
        </warning>
    </refsection>
    <refsection>
        <title>Examples</title>
        <programlisting role="example"><![CDATA[
e=1; a=1; k=1;
while norm(a-(a+e),1) > %eps,
    e=e/2;
    k=k+1;
end
e,k
 ]]></programlisting>
    </refsection>
    <refsection role="see also">
        <title>See also</title>
        <simplelist type="inline">
            <member>
                <link linkend="or_op">|, ||</link>
            </member>
            <member>
                <link linkend="and_op">&amp;, &amp;&amp;</link>
            </member>
            <member>
                <link linkend="break">break</link>
            </member>
            <member>
                <link linkend="for">for</link>
            </member>
            <member>
                <link linkend="select">select</link>
            </member>
        </simplelist>
    </refsection>
    <refsection>
        <title>History</title>
        <revhistory>
            <revision>
                <revnumber>6.0.0</revnumber>
                <revremark>
                    <itemizedlist>
                      <listitem>
                        The <literal>[,else instructions]</literal> syntax is no longer supported.
                      </listitem>
                      <listitem>
                        <literal>while</literal> is now protected:
                        Assignments like <literal>while=1</literal> are no longer possible.
                      </listitem>
                  </itemizedlist>
                </revremark>
            </revision>
        </revhistory>
    </refsection>
</refentry>
