docno|NN =|SYM "|'' lists-|NN 046|CD -|: 12158926|CD "|'' name|NN =|SYM "|'' Neil|NNP Soiffer|NNP "|'' email|NN =|SYM "|'' soiffer@wri.com|NN "|'' sent|VBD =|SYM "|'' Wed|NNP ,|, 5|CD Jun|NNP 1996|CD 19:06:49|NN -|: 0700|CD "|'' id|NN =|SYM "|'' 199606060206.AA06946@drizzle.wri.com|NN "|'' subject|JJ =|SYM "|'' Re|NNP :|: Comments|NNS on|IN parsing|VBG steps|NNS :|: "|'' To|TO :|: dsr@w3.org|NN Cc|NNP :|: w3c-math-erb@w3.org|NN >|NN >|NN Mathematica|NNP 's|POS parsing|VBG ,|, which|WDT works|VBZ in|IN a|DT manner|NN similar|JJ to|TO what|WP Bruce|NNP >|NN >|NN describes|VBZ ,|, has|VBZ no|DT problem|NN handling|VBG complex|JJ embellishments|NNS .|. 

>|NN I|PRP can|MD see|VB value|NN in|IN allowing|VBG prefix|NN and|CC postfix|NN operators|NNS to|TO act|VB as|IN >|NN operator|NN embellishments|NNS ,|, for|IN instance|NN to|TO add|VB accents|NNS to|TO operators|NNS or|CC >|NN to|TO change|VB their|PRP$ relative|JJ size|NN ,|, or|CC position|NN .|. 

>|NN If|IN these|DT embellishment|NN prefix|NN and|CC postfix|NN operators|NNS have|VBP a|DT high|JJ >|NN precedence|NN and|CC hence|RB bind|NN tightly|RB to|TO the|DT adjacent|JJ operator|NN then|RB >|NN I|PRP do|VBP n't|RB see|VB any|DT problems|NNS .|. 
Am|NNP I|PRP missing|VBG something|NN ?|. 

I|PRP think|VBP that|IN there|EX is|VBZ a|DT problem|NN with|IN prefix|NN embellishments|NNS .|. 
The|DT arguments|NNS are|VBP technical|JJ ,|, so|RB people|NNS who|WP do|VBP n't|RB care|VB can|MD stop|VB reading|VBG .|. 

When|WRB the|DT parser|NN encounters|VBZ something|NN like|IN a|DT +|NN _|NN 2|CD b|SYM ,|, it|PRP knows|VBZ by|IN the|DT time|NN of|IN reading|VBG the|NNP '|POS +|NN '|'' that|IN it|PRP must|MD have|VB a|DT right|JJ operand|NN .|. 
The|DT most|RBS reasonable|JJ "|'' error|NN correction|NN "|'' would|MD be|VB to|TO have|VB the|DT '|POS _|NN '|'' embellishe|NN '|'' +|NN '|'' .|. 

However|RB ,|, consider|VBP the|DT following|VBG :|: &|CC bold|JJ +|NN 2|CD with|IN '|POS &|CC bold|JJ '|POS being|VBG a|DT high-precedence|JJ prefix|NN operator|NN .|. 
When|WRB the|DT parser|NN sees|VBZ the|NNP '|POS +|NN '|'' ,|, it|PRP sees|VBZ that|IN it|PRP must|MD be|VB a|DT prefix|NN operator|NN ,|, and|CC so|RB will|MD shift|VB the|NNP '|POS 2|CD '|POS on|IN .|. 
So|RB ,|, this|DT expression|NN would|MD result|VB in|IN :|: {|( &|CC bold|JJ {|( +|NN 2|CD }|) }|) 

To|TO get|VB what|WP you|PRP probably|RB wanted|VBD ,|, you|PRP would|MD need|VB to|TO write|VB {|( &|CC bold|JJ +|NN }|) 2|CD 
For|IN a|DT large|JJ number|NN of|IN cases|NNS ,|, such|JJ as|IN '|POS &|CC bold|JJ x|SYM +|NN 2|CD '|POS ,|, the|DT right|JJ thing|NN would|MD happen|VB .|. 
It|PRP is|VBZ just|RB when|WRB you|PRP try|VBP to|TO embellish|VB an|DT operator|NN .|. 
A|DT high-precedence|JJ postfix|NN &|CC bold|JJ would|MD not|RB have|VB this|DT problem|NN .|. 

Since|IN the|DT details|NNS of|IN why|WRB a|DT prefix|NN embellishing|VBG operator|NN sometimes|RB "|'' works|VBZ "|'' right|NN and|CC sometimes|RB does|VBZ n't|RB are|VBP probably|RB beyond|IN most|JJS authors|NNS ,|, I|PRP think|VBP we|PRP should|MD avoid|VB them|PRP .|. 
Or|CC if|IN we|PRP must|MD have|VB them|PRP ,|, tell|VB people|NNS to|TO always|RB uses|VBZ braces|NNS to|TO properly|RB group|VB it|PRP .|. 

Neil|NNP 
