UTF8 Expect[num,arr,index,count,consumed:out]
{
	byte <- [arr]Index[index]
	{
		If[[128u8]>[byte]]
		{
			//Error: ASCII byte when we were expecting part of a mutlibyte sequence
			//treat each byte as a separate character
			ncount <- [1i32]+[[count]+[consumed]]
		}{
			If[[192u8]>[byte]]
			{
				If[[num]=[1]]
				{
					//Sequence is complete count as single character
					ncount <- [1i32]+[count]
				}{
					out <- UTF8 Expect[[num]-[1], arr, [index]+[1], count, [1i32]+[consumed]]
				}
			}{
				//Error: too high to be a continuation byte
				ncount <- [1i32]+[[count]+[consumed]]
			}
		}
	}{
		//Error: string ended in the middle of a multi-byte sequence
		out <- [count]+[consumed]
	}
	Val[ncount]
	{
		[arr]Next[index]
		{
			out <- Count UTF8[arr, ~, ncount]
		}{
			out <- Val[ncount]
		}
	}
}

Count UTF8[arr,index,count:out]
{
	byte <- [arr]Index[index]
	If[[128u8]>[byte]]
	{ ncount <- [1i32]+[count] }
	{
		If[[192u8]>[byte]]
		{
			//Error: Encoding for 2nd,3rd or 4th byte of sequence
			//treat as a single character
			ncount <- [1i32]+[count]
		}{
			If[[224u8]>[byte]]
			{
				out <- UTF8 Expect[1, arr, [index]+[1], count, 1]
			}{
				If[[240u8]>[byte]]
				{
					out <- UTF8 Expect[2, arr, [index]+[1], count, 1]
				}{
					If[[245u8]>[byte]]
					{
						out <- UTF8 Expect[3, arr, [index]+[1], count, 1]
					}{
						//Error: Out of range of Unicode standard
						//treat as a single character
						ncount <- [1i32]+[count]
					}
				}
			}
		}
	}
	[arr]Next[index]
	{
		out <- Count UTF8[arr, ~, ncount]
	}{
		out <- Val[ncount]
	}
}

Blueprint String
{
	Buffer
	Length(Int32,Naked)
}

String[in(Array):out(String)]
{
	out <- [[Build[String()]]Buffer <<[in]]Length <<[Count UTF8[in, 0, 0]]
}

Print@String[string:out]
{	
	//TODO: Sanitize string (remove terminal escapes and replace invalid UTF)
	write[1i32, [string]Buffer >>, Int64[[[string]Buffer >>]Length >>]]
	{ out <- write[1i32, [Array[]]Append[10u8], 1i64] }
}

Flatten@String[string:out]
{
	out <- string
}

Slice@String[string,slicepoint:left,right]
{
	//TODO: Handle invalid slicepoints
	left <- String Slice[string, 0i32, slicepoint]
	right <- String Slice[string, slicepoint, [[string]Length >>]-[slicepoint]]
}

Blueprint String Slice
{
	Source
	Offset(Int32,Naked)	
	Length(Int32,Naked)
}

String Slice[source,offset,length:out(String Slice)]
{
	out <- [[[Build[String Slice()]]Source <<[source]]Offset <<[offset]]Length <<[length]
}