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maybe.tex
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3 3  
4 4 To begin we provide an overview of the \texttt{maybe} statements semantics,
5 5 describing how it structures uncertainty in variable values and runtime
6   -execution. We refer to each of the values a \texttt{maybe} variable can take
7   -or paths a \texttt{maybe} code block can execute as an \textit{alternative}.
  6 +execution. We refer to each of the values or code paths a \texttt{maybe}
  7 +statement can choose from as an \textit{alternative}.
8 8  
9 9 \begin{figure}[t]
10 10 \begin{minted}[fontsize=\footnotesize]{java}
... ... @@ -22,23 +22,18 @@ int myFunction(int a) { /* Second alternative */ }
22 22 // Inlining evaluation code
23 23 maybe {
24 24 ret = fastPowerHungryAlgorithm(input);
25   - choice = FAST;
26 25 } or {
27 26 ret = slowPowerEfficientAlgorithm(input);
28   - choice = SLOW;
29 27 } analyze {
30 28 return { "repeat": false,
31 29 "score" : nanoTime() + powerDrain() }
32 30 }
33 31  
34   -// Cleanup may depend on which algorithm was used
35   -if(choice == FAST){ cleanUpAfterFastAlg(ret); }
36   -else { cleanUpAfterSlowAlg(ret); }
37 32 \end{minted}
38 33  
39 34 \vspace*{-0.2in}
40 35  
41   -\caption{\textbf{More Examples of \texttt{maybe} Statements.}}
  36 +\caption{\textbf{More \texttt{maybe} Statements}}
42 37  
43 38 \label{fig-maybeexamples}
44 39  
... ... @@ -70,36 +65,33 @@ or reorganize logic that does not affect correctness, but may (or
70 65 may not) improve performance if executed.
71 66  
72 67 Figure~\ref{fig-maybeexamples} shows several extensions of the \texttt{maybe}
73   -statement providing syntactic sugar. \texttt{maybe} function annotations allow
74   -uncertainty to be expressed at the function level, with the alternatives
75   -consisting of multiple function definitions with identical signatures. Finally,
76   -\texttt{maybe} blocks that require special performance evaluation logic can
77   -include that in the form of a \texttt{better} statement following the main
78   -\texttt{maybe}
79   -block, as shown in the final example. \texttt{better} blocks provide
80   -application-specific logic that performs a post-mortem on the selected
81   -execution path. The \texttt{better} block must return a
82   -single JSON object that includes two components: A score, with smaller being
83   -interpreted as better; and a boolean indicating whether the system should
84   -use the same branch next time, or if it is free to try another.
85   -Note that hints and dedicated evaluation logic can also be
86   -applied to variable and function-level \texttt{maybe} statements through
87   -annotations.
88   -We will return to post-mortem evaluation
89   -in Section~\ref{sec-certainty}.
  68 +statement providing syntactic sugar. \texttt{maybe} function annotations
  69 +allow uncertainty to be expressed at the function level, with the
  70 +alternatives consisting of multiple function definitions with identical
  71 +signatures. Finally, \texttt{maybe} blocks that require special performance
  72 +evaluation logic can include that in the form of a \texttt{better} statement
  73 +following the main \texttt{maybe} block, as shown in the final example.
  74 +\texttt{better} blocks provide application-specific logic that analyze the
  75 +selected execution path. The \texttt{better} block must return a single JSON
  76 +object that includes two components: A score, with smaller being interpreted
  77 +as better; and a boolean indicating whether the system should use the same
  78 +branch next time, or if it is free to try another. Note that hints and
  79 +dedicated evaluation logic can also be applied to variable and function-level
  80 +\texttt{maybe} statements through annotations. We will return to post-mortem
  81 +evaluation in Section~\ref{sec-certainty}.
90 82  
91 83 \subsection{Discussion}
92 84  
93   -We have yet to determine how well programmers will be able to use the new
94   -\texttt{maybe} construct. At some level, \texttt{maybe} statements are
95   -similar to the common \texttt{if-else} construct in that at the bottom of the
  85 +We have yet to determine how well programmers will be able to use the
  86 +\texttt{maybe} statement. Structurally \texttt{maybe} statements are similar
  87 +to the common \texttt{if-else} construct in that at the bottom of the
96 88 statement the programmer may not be sure which block was executed. However,
97 89 while with \texttt{if-else} blocks it can be determined which block was
98 90 executed by examining the branch conditions, \texttt{maybe} statements
99   -require developers record which alternative was used if downstream code
100   -depends on the decision. Alternatively, programmers may use a \texttt{maybe}
101   -variable to select a policy and employ traditional \texttt{if-else}
102   -statements to direct control flow based on the \texttt{maybe} variable.
  91 +require developers record which alternative was executed if downstream code
  92 +depends on the decision. To coordinate the adaptation of multiple code paths
  93 +a single \texttt{maybe} variable can be used to control multiple
  94 +\texttt{if-else} statements.
103 95  
104 96 While \texttt{maybe} is a powerful programming tool, it is important that it
105 97 be used sparingly. In the case where dependencies exist between the
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