/// <summary>EP message to <c>str</c>.</summary>
/// <param name="concat">Incoming message from <c>concat</c>.</param>
/// <param name="ch">Incoming message from <c>ch</c>.</param>
/// <returns>The outgoing EP message to the <c>str</c> argument.</returns>
/// <remarks>
/// <para>The outgoing message is a distribution matching the moments of <c>str</c> as the random arguments are varied. The formula is <c>proj[p(str) sum_(concat,ch) p(concat,ch) factor(concat,ch,str)]/p(str)</c>.</para>
/// </remarks>
public static StringDistribution StrAverageConditional(StringDistribution concat, DiscreteChar ch)
{
return(StringConcatOp.Str2AverageConditional(concat, StringDistribution.Char(ch)));
}
/// <summary>EP message to <c>ch</c>.</summary>
/// <param name="concat">Incoming message from <c>concat</c>.</param>
/// <param name="str">Incoming message from <c>str</c>.</param>
/// <returns>The outgoing EP message to the <c>ch</c> argument.</returns>
/// <remarks>
/// <para>The outgoing message is a distribution matching the moments of <c>ch</c> as the random arguments are varied. The formula is <c>proj[p(ch) sum_(concat,str) p(concat,str) factor(concat,str,ch)]/p(ch)</c>.</para>
/// </remarks>
public static DiscreteChar ChAverageConditional(StringDistribution concat, StringDistribution str)
{
var result = StringConcatOp.Str2AverageConditional(concat, str);
return(SingleOp.CharacterAverageConditional(result));
}