Why are the branches of the if statement not implemented consistently?

[pjljvandelaar]

Dear JSONCPP developers,

I was looking at the following if statement starting on

jsoncpp/src/lib_json/json_writer.cpp

Line 734 in 69098a1

if (isArrayMultiLine) {

It took me some time to realize that the rather complex code in the then branch:

jsoncpp/src/lib_json/json_writer.cpp

Lines 738 to 757 in 69098a1

	unsigned index = 0;
	for (;;) {
	const Value& childValue = value[index];
	writeCommentBeforeValue(childValue);
	if (hasChildValue)
	writeWithIndent(childValues_[index]);
	else {
	if (!indented_)
	writeIndent();
	indented_ = true;
	writeValue(childValue);
	indented_ = false;
	}
	if (++index == size) {
	writeCommentAfterValueOnSameLine(childValue);
	break;
	}
	*document_ << ",";
	writeCommentAfterValueOnSameLine(childValue);
	}

is equal to joining the elements in the range [0,size) where size != 0 with a separator,
and a functional equivalent, yet simpler, implementation is

      for (unsigned index = 0; index < size ; ++index) {
        const Value& childValue = value[index];
        writeCommentBeforeValue(childValue);
        if (hasChildValue)
          writeWithIndent(childValues_[index]);
        else {
          if (!indented_)
            writeIndent();
          indented_ = true;
          writeValue(childValue);
          indented_ = false;
        }
        if (index < size -1) {
           *document_ << ",";
        }
        writeCommentAfterValueOnSameLine(childValue);
      }

I assume performance (saving a comparison) is the reason for the extra complexity.

Yet, when looking at the else branch

jsoncpp/src/lib_json/json_writer.cpp

Lines 764 to 768 in 69098a1

	for (unsigned index = 0; index < size; ++index) {
	if (index > 0)
	*document_ << ", ";
	*document_ << childValues_[index];
	}

that is not optimized, like the then branch, to

      unsigned index = 0;
      for (;;) {
        *document_ << childValues_[index];
        if (++index == size)
		break;
        *document_ << ", ";
      }

So I wonder

1. what is more important for jsoncpp code: readability or performance?
2. Shouldn't these two branches not be implemented consistently?

Thanks in advance for your answers (and possibly code improvements)!