Precedences: * > . > +
Example:
((a.(a*) ) + ((b*).b)) can be written as a .a* + b*.b ,
and a .a* + b*.b can be written as a+ + b+
1) Reduction of the number of parentheses by
3) Expression rr* or r*r is simplified to r+ 
Simplification
2) Expression r.s is simplified to rs
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