Недостатки чистого функционального программирования

static void Main ( string [ ] args )
{
    Console.WriteLine ( "Test string speed." );
    Console.WriteLine ( "Input string part:" );
    string part = Console.ReadLine ( );
    Console.WriteLine ( "Input delimeter:" );
    string delim = Console.ReadLine ( );

    //string
    Console.WriteLine ( "Input count for string:" );
    int sCount = 0;
    try
    {
        sCount = Int32.Parse ( Console.ReadLine ( ) );
    }
    catch { }
    string result = "";
    DateTime sBegin = DateTime.Now;
    Console.WriteLine ( "Test string start with "+sCount+" iteration... ["+sBegin+"]" );
    for (int i = 0; i<sCount; ++i )
    {
        result += part + delim;
    }
    DateTime sEnd = DateTime.Now;
    Console.WriteLine ( "Test string end. "+sCount+" iteration passed. [" + sEnd + "]" );
    Console.WriteLine ( "Result string length:" );
    Console.WriteLine ( result.Length );
    Console.WriteLine ( "Time Passed:" + ( sEnd - sBegin ) );

    //StringBuilder
    Console.WriteLine ( "Input count for builder. Input \"0\" if you want to keep current count("+sCount+"):" );
    int bCount = 0;
    try
    {
        bCount = Int32.Parse ( Console.ReadLine ( ) );
    }
    catch { }
    if ( bCount == 0 ) bCount = sCount;
    string bResult = "";
    StringBuilder builder = new StringBuilder();
    DateTime bBegin = DateTime.Now;
    Console.WriteLine ( "Test StringBuilder start with " + bCount + " iteration... [" + bBegin+"]" );
    for ( int i = 0; i < bCount; ++i )
    {
        builder.Append ( part );
        builder.Append ( delim );
    }
    bResult = builder.ToString ( );
    DateTime bEnd = DateTime.Now;
    Console.WriteLine ( "Test StringBuilder end. " + bCount + " iteration passed. [" + bEnd + "]" );
    Console.WriteLine ( "Builder Result length:" );
    Console.WriteLine ( bResult.Length );
    Console.WriteLine ( "Time Passed:" + ( bEnd - bBegin ) );
    
    //Result
    Console.WriteLine ( );
    Console.WriteLine ( "-------------------------------------------------" );
    Console.WriteLine ( );
    Console.WriteLine ( "Simple string time:" + ( sEnd - sBegin ) + "with " + sCount + " of iterations." );
    Console.WriteLine ( "StringBuilder time:" + ( bEnd - bBegin ) + "with " + bCount + " of iterations." );
    Console.WriteLine ( );
    Console.WriteLine ( "Press any key" );
    Console.ReadKey ( );
}

private void MakeRoom(int index, int count, out StringBuilder chunk, out int indexInChunk, bool doneMoveFollowingChars)
{
...

    chunk = this;
    while (chunk.m_ChunkOffset > index)
    {
            chunk.m_ChunkOffset += count;
            chunk = chunk.m_ChunkPrevious;
    }
    indexInChunk = index - chunk.m_ChunkOffset;
     
    // Cool, we have some space in this block, and you don't have to copy much to get it, go ahead
    // and use it.  This happens typically  when you repeatedly insert small strings at a spot
    // (typically the absolute front) of the buffer.    
    if (!doneMoveFollowingChars && chunk.m_ChunkLength <= DefaultCapacity * 2 && chunk.m_ChunkChars.Length - chunk.m_ChunkLength >= count)
    {
            for (int i = chunk.m_ChunkLength; i > indexInChunk; )
            {
                    --i;
                    chunk.m_ChunkChars[i + count] = chunk.m_ChunkChars[i];
            }
            chunk.m_ChunkLength += count;
            return;
    }

...
}