20101109

20101109 - = CS 441 Fall 2010 - JWJ Pre-class notes - do...

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============================ CS 441 Fall 2010 -- JWJ Pre-class notes - do not distribute Tuesday, November 9, 2010 ============================ Topics Syntax-directed translation. S-attributed syntax-directed definition, L-attributed syntax-directed definition YACC and Bison Concepts/Definitions A warm-up exercise: write a program to compute the length of the list. Write two recursive functions: one that returns the value, the other that uses one of the arguments to compute the length. Constructing syntax-trees for with syntax-directed definitions E --> E_1 + T E.nptr = mknode(+, E_1.nptr, T.nptr) E -> T E.nptr = T.nptr T -> ( T ) T.nptr = E.nptr T -> id T.nptr = mkleaf(id, id.entry) Exercise -- construct a syntax tree for b + 5 + ( c ) Potential issues with evaluationg attributes: - an inherited atribute for a symbol on the RHS must be computed in action before that symbol - an action cannot use a synthesized attribute of the symbol to its (the action) right - the syntesized attribute of the LHS nonterminal can be computed only after
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20101109 - = CS 441 Fall 2010 - JWJ Pre-class notes - do...

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