about assign direction types for characters

[li bo]

Hi,

I have read the reference code for BIDI algorithm implement in
http://www.unicode.org/Public/PROGRAMS/BidiReferenceCpp/

I'm confused about some codes in Bidi.cpp.

Before determining embedding levels for characters, assign directional types
like this
        // assign directional types
        classify(pszInput, types, cch);
And after determining embedding levels, assign directional types again ,but
for WS,S
        // assign directional types again, but for WS, S this time
        classify(pszInput, types, cch, true);

Why not assign directional types for WS and S in the first time?

Thanks


alex