/// <summary>
/// Creates formatting function for sequence which applies provided formatter to every sequence item
/// and joins results with <paramref name="glue"/>.
/// </summary>
/// <param name="fmt">Formats individual sequence elements.</param>
/// <param name="glue">Joins formatter results applied to subsequent items.</param>
/// <typeparam name="T">Type of collection elements.</typeparam>
public static Formatter <IEnumerable <T> > Collect <T>(Formatter <T> fmt, Writer glue = null)
{
glue = glue ?? WriteWhitespace;
return(seq => seq
.Select(fmt.Invoke)
.Aggregate((a, b) => IsEmpty(b) ? a : Writers.Sum(a, glue, b)));
}
/// <summary>
/// Combines 2 formatting function into one by applying them in sequence and executing <paramref name="separator"/>
/// <see cref="Writer"/> in between. If any <see cref="Formatter{T}"/> results in empty <see cref="Writer"/>
/// than only one (the other) will be applied.
/// </summary>
/// <param name="first"><see cref="Formatter{T}"/> function applied first.</param>
/// <param name="second"><see cref="Formatter{T}"/> function applied second.</param>
/// <param name="separator"><see cref="Writer"/> function applied in between.</param>
/// <typeparam name="T">Formatted value type.</typeparam>
public static Formatter <T> Join <T>(Formatter <T> first, Formatter <T> second, Writer separator)
{
return(obj =>
{
var firstWriter = first?.Invoke(obj);
var secondWriter = second?.Invoke(obj);
return IsEmpty(secondWriter)
? firstWriter
: IsEmpty(firstWriter)
? secondWriter
: Writers.Sum(firstWriter, separator, secondWriter);
});
}
/// <summary> /// Converts formatting function to function returning string representation of formatted value accumulated in /// <see cref="StringBuilder"/> by formatting function. /// </summary> /// <param name="formatter">Formatting function.</param> /// <returns>Function returning string representation of formatted value.</returns> public static Func <T, string> MakeToString <T>(Formatter <T> formatter) => o => Writers.ToString(formatter?.Invoke(o));
