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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:db="http://docbook.org/ns/docbook"
          xmlns:scilab="http://www.scilab.org" xml:lang="en" xml:id="setfield">
    <refnamediv>
        <refname>setfield</refname>
        <refpurpose>change the value of an element of a mlist, tlist or list</refpurpose>
    </refnamediv>
    <refsynopsisdiv>
        <title>Syntax</title>
        <synopsis>uL = setfield(a, v, L)</synopsis>
    </refsynopsisdiv>
    <refsection>
        <title>Arguments</title>
        <variablelist>
            <varlistentry>
                <term>L</term>
                <listitem>
                    a <literal>list</literal>, <literal>tlist</literal> or <literal>mlist</literal>
                    list: the list whose component must be changed.
                    <para/>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>a</term>
                <listitem>
                    Address of the component to change. It can be either its field name
                    specified as a string, or its index specified as a positive integer.
                    See <link linkend="insertion">insertion</link> for more details.
                    <para/>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>v</term>
                <listitem>
                    Any Scilab object: the value to assign.
                    <para/>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>uL</term>
                <listitem>
                    The updated list.
                    <para/>
                </listitem>
            </varlistentry>
        </variablelist>
    </refsection>
    <refsection>
        <title>Description</title>
        <para>
            <literal>L=setfield(a,v,L)</literal> addresses and changes the
            i<superscript>th</superscript> element of a list, in a unified way
            over lists, tlists and mlists.
        </para>
        <para>
            For simple lists and for tlists, <literal>L=setfield(a,v,L)</literal>
            is equivalent to <literal>L(a)=v</literal>, that is simpler and should be preferred.
            The same stands for any mlist if the address <varname>a</varname> is a
            field's name.
        </para>
        <para>
            However, for any mlist L, if <literal>i</literal> is an index, the insertion
            <literal>L(i)=v</literal> is not predefined, in order to let the user define
            an overload implementing a matrix-oriented insertion, if required.
            Yet <literal>setfield(i,v,L)</literal> is always defined, with the same meaning as
            for other list and tlist types.
        </para>
    </refsection>
    <refsection>
        <title>Examples</title>
        <para>
            For a tlist, <literal>setfield(3, v, T)</literal> is equivalent to
            <literal>T(3)=v</literal> :
        </para>
        <programlisting role="example"><![CDATA[
T = tlist(['V','a','b'], [%z (1-%z) %z^2], [%f %t %t]);
// The insertion is predefined:
T(3) = [%t %t %f];
T(3)

T = setfield(3, [%f %t %f], T);
T(3)
 ]]></programlisting>
    <screen><![CDATA[
--> T = tlist(['V','a','b'], [%z (1-%z) %z^2], [%f %t %t]);
--> // The insertion is predefined:
--> T(3) = [%t %t %f];
--> T(3)
 ans  =
  T T F

--> T = setfield(3, [%f %t %f], T);
--> T(3)
 ans  =
  F T F
]]></screen>
        <para>
            For a mlist, there is no predefined indexed insertion routine, to
            let the user define a matrix-oriented insertion overload if required.
        </para>
        <programlisting role="example"><![CDATA[
M = mlist(['V','a','b'], [%z (1-%z) %z^2], [%f %t %t]);
M.b = [%t %t %t];
M.b                 // OK, while ...
M(3) = [%f %t %f];  // => error

// But a raw direct insertion with setfield() is always possible:
M = setfield(3, [%t %f %t], M);
getfield(3, M)
 ]]></programlisting>
    <screen><![CDATA[
--> M = mlist(['V','a','b'], [%z (1-%z) %z^2], [%f %t %t]);
--> M.b = [%t %t %t];
--> M.b                 // OK, while ...
 ans  =
  T T T

--> M(3) = [%f %t %f];  // => error
Function not defined for given argument type(s),
  check arguments or define function %b_i_V for overloading.

--> // But a raw direct insertion with setfield() is always possible:
--> M = setfield(3, [%t %f %t], M);
--> getfield(3, M)
 ans  =
  T F T
]]></screen>
    </refsection>
    <refsection role="see also">
        <title>See also</title>
        <simplelist type="inline">
            <member>
                <link linkend="insertion">insertion</link>
            </member>
            <member>
                <link linkend="getfield">getfield</link>
            </member>
        </simplelist>
    </refsection>
    <refsection>
        <title>History</title>
        <revhistory>
            <revision>
                <revnumber>6.0.0</revnumber>
                <revdescription>
                    <itemizedlist>
                        <listitem>
                            The updated list is now returned, instead of being changed "in place".
                        </listitem>
                        <listitem>
                            setfield() can no longer be used for cells arrays.
                        </listitem>
                    </itemizedlist>
                </revdescription>
            </revision>
        </revhistory>
    </refsection>
</refentry>
