 Timestamp:
 Apr 24, 2019, 9:31:21 PM (3 years ago)
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 aaronthesis, armeh, cleanupdtors, enum, forallpointerdecay, jacob/cs343translation, jenkinssandbox, master, newast, newastuniqueexpr
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 69c37cc
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 39de1c5
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doc/theses/aaron_moss_PhD/phd/resolutionheuristics.tex
r39de1c5 r5d3a952 46 46 47 47 \begin{itemize} 48 \item If either operand is a floatingpoint type, the common type is the size of the largest floatingpoint type. If either operand is !_Complex!, the common type is also !_Complex!.48 \item If either operand is a floatingpoint type, the common type is the size of the largest floatingpoint type. If either operand is !_Complex!, the common type is also \linebreak !_Complex!. 49 49 \item If both operands are of integral type, the common type has the same size\footnote{Technically, the C standard defines a notion of \emph{rank} in \cite[\S{}6.3.1.1]{C11}, a distinct value for each \lstinline{signed} and \lstinline{unsigned} pair; integral types of the same size thus may have distinct ranks. For instance, though \lstinline{int} and \lstinline{long} may have the same size, \lstinline{long} always has greater rank. The standarddefined types are declared to have greater rank than any types of the same size added as compiler extensions.} as the larger type. 50 50 \item If the operands have opposite signedness, the common type is !signed! if the !signed! operand is strictly larger, or !unsigned! otherwise. If the operands have the same signedness, the common type shares it. … … 106 106 107 107 \begin{cfa} 108 forall(otype T, otype U) void f$\(_1\)$(T, U); $\C[3. 25in]{// polymorphic}$109 forall(otype T) void f$\(_2\)$(T, T); $\C[3. 25in]{// less polymorphic}$110 forall(otype T) void f$\(_3\)$(T, int); $\C[3. 25in]{// even less polymorphic}$111 forall(otype T) void f$\(_4\)$(T*, int); $\C[3. 25in]{// least polymorphic}$108 forall(otype T, otype U) void f$\(_1\)$(T, U); $\C[3.125in]{// polymorphic}$ 109 forall(otype T) void f$\(_2\)$(T, T); $\C[3.125in]{// less polymorphic}$ 110 forall(otype T) void f$\(_3\)$(T, int); $\C[3.125in]{// even less polymorphic}$ 111 forall(otype T) void f$\(_4\)$(T*, int); $\C[3.125in]{// least polymorphic}$ 112 112 \end{cfa} 113 113 … … 196 196 \end{cfa} 197 197 198 In C semantics, this example is unambiguously upcasting !32! to !unsigned long long!, performing the shift, then downcasting the result to !unsigned!, at totalcost $(1,0,3,1,0,0,0)$.198 In C semantics, this example is unambiguously upcasting !32! to !unsigned long long!, performing the shift, then downcasting the result to !unsigned!, at cost $(1,0,3,1,0,0,0)$. 199 199 If ascription were allowed to be a firstclass interpretation of a cast expression, it would be cheaper to select the !unsigned! interpretation of !?>>?! by downcasting !x! to !unsigned! and upcasting !32! to !unsigned!, at a total cost of $(1,0,1,1,0,0,0)$. 200 200 However, this break from C semantics is not backwards compatibile, so to maintain C compatibility, the \CFA{} resolver selects the lowestcost interpretation of the cast argument for which a conversion or coercion to the target type exists (upcasting to !unsigned long long! in the example above, due to the lack of unsafe downcasts), using the cost of the conversion itself only as a tiebreaker.
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