Add examples of doing record updates

docs/ProgrammingCryptol/appendices/Syntax.tex

@@ -2,8 +2,7 @@
 % markdown in ../../Syntax.md.   If you make changes, please make them
 % there and then regenerate the .tex file using the Makefile.
 
-\hypertarget{layout}{%
-\section{Layout}\label{layout}}
+\section{Layout}\label{layout}
 
 Groups of declarations are organized based on indentation. Declarations
 with the same indentation belong to the same group. Lines of text that
@@ -33,8 +32,7 @@ containing \texttt{y} and \texttt{z}. This group ends just before
 \texttt{g}, because \texttt{g} is indented less than \texttt{y} and
 \texttt{z}.
 
-\hypertarget{comments}{%
-\section{Comments}\label{comments}}
+\section{Comments}\label{comments}
 
 Cryptol supports block comments, which start with \texttt{/*} and end
 with \texttt{*/}, and line comments, which start with \texttt{//} and
@@ -49,8 +47,7 @@ Examples:
 /* This is a /* Nested */ block comment */
 \end{verbatim}
 
-\hypertarget{identifiers}{%
-\section{Identifiers}\label{identifiers}}
+\section{Identifiers}\label{identifiers}
 
 Cryptol identifiers consist of one or more characters. The first
 character must be either an English letter or underscore (\texttt{\_}).
@@ -67,9 +64,8 @@ name    name1    name'    longer_name
 Name    Name2    Name''   longerName
 \end{verbatim}
 
-\hypertarget{keywords-and-built-in-operators}{%
-\section{Keywords and Built-in
-Operators}\label{keywords-and-built-in-operators}}
+\hypertarget{keywords-and-built-in-operators}{\section{Keywords and
+Built-in Operators}\label{keywords-and-built-in-operators}}
 
 The following identifiers have special meanings in Cryptol, and may not
 be used for programmer defined names:
@@ -120,9 +116,8 @@ left\tabularnewline
 \bottomrule
 \end{longtable}
 
-\hypertarget{built-in-type-level-operators}{%
 \section{Built-in Type-level
-Operators}\label{built-in-type-level-operators}}
+Operators}\label{built-in-type-level-operators}
 
 Cryptol includes a variety of operators that allow computations on the
 numeric types used to specify the sizes of sequences.
@@ -154,8 +149,7 @@ up)\tabularnewline
 \bottomrule
 \end{longtable}
 
-\hypertarget{numeric-literals}{%
-\section{Numeric Literals}\label{numeric-literals}}
+\section{Numeric Literals}\label{numeric-literals}
 
 Numeric literals may be written in binary, octal, decimal, or
 hexadecimal notation. The base of a literal is determined by its prefix:
@@ -188,8 +182,7 @@ is inferred from context in which the literal is used. Examples:
                     // a = Integer or [n] where n >= width 10
 \end{verbatim}
 
-\hypertarget{bits}{%
-\section{Bits}\label{bits}}
+\section{Bits}\label{bits}
 
 The type \texttt{Bit} has two inhabitants: \texttt{True} and
 \texttt{False}. These values may be combined using various logical
@@ -220,8 +213,7 @@ Operator & Associativity & Description\tabularnewline
 \bottomrule
 \end{longtable}
 
-\hypertarget{multi-way-conditionals}{%
-\section{Multi-way Conditionals}\label{multi-way-conditionals}}
+\section{Multi-way Conditionals}\label{multi-way-conditionals}
 
 The \texttt{if\ ...\ then\ ...\ else} construct can be used with
 multiple branches. For example:
@@ -235,8 +227,7 @@ x = if y % 2 == 0 then 1
      else 7
 \end{verbatim}
 
-\hypertarget{tuples-and-records}{%
-\section{Tuples and Records}\label{tuples-and-records}}
+\section{Tuples and Records}\label{tuples-and-records}
 
 Tuples and records are used for packaging multiple values together.
 Tuples are enclosed in parentheses, while records are enclosed in curly
@@ -264,6 +255,8 @@ of record components is not important. Examples:
 { x = 1, y = 2 } == { y = 2, x = 1 }    // True
 \end{verbatim}
 
+\subsection{Accessing Fields}\label{accessing-fields}
+
 The components of a record or a tuple may be accessed in two ways: via
 pattern matching or by using explicit component selectors. Explicit
 component selectors are written as follows:
@@ -306,8 +299,30 @@ f p = x + y where
     (x, y) = p
 \end{verbatim}
 
-\hypertarget{sequences}{%
-\section{Sequences}\label{sequences}}
+\subsection{Updating Fields}\label{updating-fields}
+
+The components of a record or a tuple may be updated using the following
+notation:
+
+\begin{verbatim}
+// Example values
+r = { x = 15, y = 20 }      // a record
+t = (True,True)             // a tuple
+n = { pt = r, size = 100 }  // nested record
+
+// Setting fields
+{ r | x = 30 }          == { x = 30, y = 20 }
+{ t | 0 = False }       == (False,True)
+
+// Update relative to the old value
+{ r | x -> x + 5 }      == { x = 20, y = 20 }
+
+// Update a nested field
+{ n | pt.x = 10 }       == { pt = { x = 10, y = 20 }, size = 100 }
+{ n | pt.x -> x + 10 }  == { pt = { x = 25, y = 20 }, size = 100 }
+\end{verbatim}
+
+\section{Sequences}\label{sequences}
 
 A sequence is a fixed-length collection of elements of the same type.
 The type of a finite sequence of length \texttt{n}, with elements of
@@ -368,16 +383,14 @@ There are also lifted pointwise operations.
 p1 # p2                   // Split sequence pattern
 \end{verbatim}
 
-\hypertarget{functions}{%
-\section{Functions}\label{functions}}
+\section{Functions}\label{functions}
 
 \begin{verbatim}
 \p1 p2 -> e              // Lambda expression
 f p1 p2 = e              // Function definition
 \end{verbatim}
 
-\hypertarget{local-declarations}{%
-\section{Local Declarations}\label{local-declarations}}
+\section{Local Declarations}\label{local-declarations}
 
 \begin{verbatim}
 e where ds
@@ -387,9 +400,7 @@ Note that by default, any local declarations without type signatures are
 monomorphized. If you need a local declaration to be polymorphic, use an
 explicit type signature.
 
-\hypertarget{explicit-type-instantiation}{%
-\section{Explicit Type
-Instantiation}\label{explicit-type-instantiation}}
+\section{Explicit Type Instantiation}\label{explicit-type-instantiation}
 
 If \texttt{f} is a polymorphic value with type:
 
@@ -404,9 +415,8 @@ you can evaluate \texttt{f}, passing it a type parameter:
 f `{ tyParam = 13 }
 \end{verbatim}
 
-\hypertarget{demoting-numeric-types-to-values}{%
 \section{Demoting Numeric Types to
-Values}\label{demoting-numeric-types-to-values}}
+Values}\label{demoting-numeric-types-to-values}
 
 The value corresponding to a numeric type may be accessed using the
 following notation:
@@ -423,8 +433,7 @@ accommodate the value of the type:
 `t : {n} (fin n, n >= width t) => [n]
 \end{verbatim}
 
-\hypertarget{explicit-type-annotations}{%
-\section{Explicit Type Annotations}\label{explicit-type-annotations}}
+\section{Explicit Type Annotations}\label{explicit-type-annotations}
 
 Explicit type annotations may be added on expressions, patterns, and in
 argument definitions.
@@ -437,22 +446,19 @@ p : t
 f (x : t) = ...
 \end{verbatim}
 
-\hypertarget{type-signatures}{%
-\section{Type Signatures}\label{type-signatures}}
+\section{Type Signatures}\label{type-signatures}
 
 \begin{verbatim}
 f,g : {a,b} (fin a) => [a] b
 \end{verbatim}
 
-\hypertarget{type-synonym-declarations}{%
-\section{Type Synonym Declarations}\label{type-synonym-declarations}}
+\section{Type Synonym Declarations}\label{type-synonym-declarations}
 
 \begin{verbatim}
 type T a b = [a] b
 \end{verbatim}
 
-\hypertarget{modules}{%
-\section{Modules}\label{modules}}
+\section{Modules}\label{modules}
 
 A \textbf{\emph{module}} is used to group some related definitions.
 
@@ -465,8 +471,7 @@ f : [8]
 f = 10
 \end{verbatim}
 
-\hypertarget{hierarchical-module-names}{%
-\section{Hierarchical Module Names}\label{hierarchical-module-names}}
+\section{Hierarchical Module Names}\label{hierarchical-module-names}
 
 Module may have either simple or \textbf{\emph{hierarchical}} names.
 Hierarchical names are constructed by gluing together ordinary
@@ -485,8 +490,7 @@ when searching for module \texttt{Hash::SHA256}, Cryptol will look for a
 file named \texttt{SHA256.cry} in a directory called \texttt{Hash},
 contained in one of the directories specified by \texttt{CRYPTOLPATH}.
 
-\hypertarget{module-imports}{%
-\section{Module Imports}\label{module-imports}}
+\section{Module Imports}\label{module-imports}
 
 To use the definitions from one module in another module, we use
 \texttt{import} declarations:
@@ -507,8 +511,7 @@ import M  // import all definitions from `M`
 g = f   // `f` was imported from `M`
 \end{verbatim}
 
-\hypertarget{import-lists}{%
-\section{Import Lists}\label{import-lists}}
+\section{Import Lists}\label{import-lists}
 
 Sometimes, we may want to import only some of the definitions from a
 module. To do so, we use an import declaration with an
@@ -532,8 +535,7 @@ Using explicit import lists helps reduce name collisions. It also tends
 to make code easier to understand, because it makes it easy to see the
 source of definitions.
 
-\hypertarget{hiding-imports}{%
-\section{Hiding Imports}\label{hiding-imports}}
+\section{Hiding Imports}\label{hiding-imports}
 
 Sometimes a module may provide many definitions, and we want to use most
 of them but with a few exceptions (e.g., because those would result to a
@@ -556,8 +558,7 @@ import M hiding (h) // Import everything but `h`
 x = f + g
 \end{verbatim}
 
-\hypertarget{qualified-module-imports}{%
-\section{Qualified Module Imports}\label{qualified-module-imports}}
+\section{Qualified Module Imports}\label{qualified-module-imports}
 
 Another way to avoid name collisions is by using a
 \textbf{\emph{qualified}} import.
@@ -600,8 +601,7 @@ Such declarations will introduces all definitions from \texttt{A} and
 \texttt{X} but to use them, you would have to qualify using the prefix
 \texttt{B:::}.
 
-\hypertarget{private-blocks}{%
-\section{Private Blocks}\label{private-blocks}}
+\section{Private Blocks}\label{private-blocks}
 
 In some cases, definitions in a module might use helper functions that
 are not intended to be used outside the module. It is good practice to
@@ -642,8 +642,7 @@ private
   helper2 = 3
 \end{verbatim}
 
-\hypertarget{parameterized-modules}{%
-\section{Parameterized Modules}\label{parameterized-modules}}
+\section{Parameterized Modules}\label{parameterized-modules}
 
 \begin{verbatim}
 module M where
@@ -661,9 +660,7 @@ f : [n]
 f = 1 + x
 \end{verbatim}
 
-\hypertarget{named-module-instantiations}{%
-\section{Named Module
-Instantiations}\label{named-module-instantiations}}
+\section{Named Module Instantiations}\label{named-module-instantiations}
 
 One way to use a parameterized module is through a named instantiation:
 
@@ -700,9 +697,8 @@ Note that the only purpose of the body of \texttt{N} (the declarations
 after the \texttt{where} keyword) is to define the parameters for
 \texttt{M}.
 
-\hypertarget{parameterized-instantiations}{%
 \section{Parameterized
-Instantiations}\label{parameterized-instantiations}}
+Instantiations}\label{parameterized-instantiations}
 
 It is possible for a module instantiations to be itself parameterized.
 This could be useful if we need to define some of a module's parameters
@@ -737,9 +733,8 @@ In this case \texttt{N} has a single parameter \texttt{x}. The result of
 instantiating \texttt{N} would result in instantiating \texttt{M} using
 the value of \texttt{x} and \texttt{12} for the value of \texttt{y}.
 
-\hypertarget{importing-parameterized-modules}{%
 \section{Importing Parameterized
-Modules}\label{importing-parameterized-modules}}
+Modules}\label{importing-parameterized-modules}
 
 It is also possible to import a parameterized module without using a
 module instantiation:

docs/Syntax.md

@@ -234,6 +234,10 @@ ordering of record components is not important.  Examples:
     { x = 1, y = 2 } == { x = 1, y = 2 }    // True
     { x = 1, y = 2 } == { y = 2, x = 1 }    // True
 
+
+Accessing Fields
+----------------
+
 The components of a record or a tuple may be accessed in two ways: via
 pattern matching or by using explicit component selectors.  Explicit
 component selectors are written as follows:
@@ -270,6 +274,31 @@ patterns use braces.  Examples:
     f p = x + y where
         (x, y) = p
 
+
+Updating Fields
+---------------
+
+The components of a record or a tuple may be updated using the following
+notation:
+
+    // Example values
+    r = { x = 15, y = 20 }      // a record
+    t = (True,True)             // a tuple
+    n = { pt = r, size = 100 }  // nested record
+
+    // Setting fields
+    { r | x = 30 }          == { x = 30, y = 20 }
+    { t | 0 = False }       == (False,True)
+
+    // Update relative to the old value
+    { r | x -> x + 5 }      == { x = 20, y = 20 }
+
+    // Update a nested field
+    { n | pt.x = 10 }       == { pt = { x = 10, y = 20 }, size = 100 }
+    { n | pt.x -> x + 10 }  == { pt = { x = 25, y = 20 }, size = 100 }
+
+
+
 Sequences
 =========