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hw7soln

# hw7soln - inherited idlist.type:= type.spectype vardcl:=...

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CS 415 Spring 2007 HW#5 Solution 1. (i) Problem 4.3.1 Using the the following grammar and actions show what the input a - (b + c) produces. E0 -> E1 + T { E0.nptr := mknode(+, E1.nptr, T.nptr) } E0 -> E1 - T { E0.nptr := mkdone(-, E1.nptr, T.nptr) } E -> T { E.nptr := T.nptr } T -> ( E ) { T.nptr := E.nptr } T -> id { T.nptr := mkleaf(id, id.entry) } - id a + id b id c left right left right

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2. stype.spectype := DOUBLE synthesized stype ::= double synthesized stype.spectype := REAL stype ::= real stype.spectype := INTEGER stype ::= integer synthesized synthesized type ::= stype type.spectype := stype.spectype type ::= array [ICONST1 .. ICONST2] of stype type.spec := array(stype.spec, ICONST1, ICONST2) synthesized inherited idlist ::= ID ID.type = idlist.type idlist0 ::= idlist1, ID inherited inherited idlist1.type := idlist0.type ID.type := idlist0.type
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Unformatted text preview: inherited idlist.type := type.spectype vardcl ::= idlist : type Problem 2. (ii) Decorated tree for A, B, C : real. Red lines are inherited. Blues line are synthesized. vardcl idlist type: REAL type spectype: REAL : stype spectype: REAL real idlist type: REAL ID type: REAL , ID type: REAL , idlist type: REAL ID type: REAL Problem 2. (iii) The solution neither S-attributed nor L-attributed. S-attributed grammars have no inherited attributes at all. The solution has inherited attributes. L-attributed grammars have left-to-right dataﬂow. The solution has right-to-left dataﬂow. Notice if the top level production rule was vardcl::= type : idlist then the dataﬂow would be left to right, and could be implemented using a L-attributed grammar....
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