add indexers and ranges

Author: RexJaeschke

standard/expressions.md

@@ -3083,7 +3083,7 @@ An *anonymous_method_expression* is one of two ways of defining an anonymous fun
 
 ### 11.8.1 General
 
-The `+`, `-`, `!`, `~`, `++`, `--`, cast, and `await` operators are called the unary operators.
+The `+`, `-`, `!`, `~`, `^`, `++`, `--`, cast, and `await` operators are called the unary operators.
 
 ```ANTLR
 unary_expression
@@ -3092,6 +3092,7 @@ unary_expression
     | '-' unary_expression
     | '!' unary_expression
     | '~' unary_expression
+    | '^' unary_expression
     | pre_increment_expression
     | pre_decrement_expression
     | cast_expression
@@ -3363,7 +3364,10 @@ At run-time, the expression `await t` is evaluated as follows:
 An awaiter’s implementation of the interface methods `INotifyCompletion.OnCompleted` and `ICriticalNotifyCompletion.UnsafeOnCompleted` should cause the delegate `r` to be invoked at most once. Otherwise, the behavior of the enclosing async function is undefined.
 
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+>>>>>>> 50008cc (add indexers and ranges)
 ## §range-operator Range operator
 
 This operator provides a succinct syntax for specifying a (possibly empty) element range suitable for use in denoting a slice of an indexable sequence (§indexable-sequence).
@@ -3381,36 +3385,56 @@ For an operation of the form `s .. e`, binary operator overload resolution ([§1
 System.Range operator ..(System.Index start = 0, System.Index end = ^0);
 ```
 
+<<<<<<< HEAD
 The left and right operands denote, respectively, a start and end Index. For this operator, an object of (the immutable struct) type `System.Range` is returned that contains those Indexes. If the left operand is omitted, an Index of `0` is used. If the right operand is omitted, an Index of `^0` is used. As such,
 
 - `s .. e` is transformed by the implementation to `new System.Range(s, e)`.
 - `s ..` is transformed by the implementation to `new System.Range(s, ^0)` (or to `System.Range.StartAt(s)` if that method exists, is accessible, and is declared as follows: `public static Range StartAt (Index start);`).
 - `.. e` is transformed by the implementation to `new System.Range(0, e)` (or to `System.Range.EndAt(e)` if that method exists, is accessible, and is declared as follows: `public static Range EndAt (Index end);`).
 - `..` is transformed by the implementation to `new System.Range(0, ^0)` (or instead to `System.Range.All` if that property exists, is accessible, and is declared as follows: `public static Range All { get; }`).
+=======
+The left and right operands denote, respectively, a start and end Index. For this operator, an object of (the immutable struct) type `System.Range` is returned that contains those Indexes. If the left operand is omitted, an Index of `0` is used. If the right operand is omitted, an Index of `^0` is used. As such, 
+-  `s .. e` is transformed by the implementation to `new System.Range(s, e)`.
+-  `s ..` is transformed by the implementation to `new System.Range(s, ^0)` (or to ` System.Range.StartAt(s)` if that method exists, is accessible, and is declared as follows: `public static Range StartAt (Index start);`).
+-  `.. e` is transformed by the implementation to `new System.Range(0, e)` (or to ` System.Range.EndAt(e)` if that method exists, is accessible, and is declared as follows: `public static Range EndAt (Index end);`).
+-  `..` is transformed by the implementation to `new System.Range(0, ^0)` (or instead to ` System.Range.All` if that property exists, is accessible, and is declared as follows: `public static Range All { get; }`).
+>>>>>>> 50008cc (add indexers and ranges)
 
 > *Note*: While a Range can be created with a start Index greater than the end Index, any attempt to use that Range to denote a slice from an indexable sequence will result in `System.ArgumentOutOfRangeException`. *end note*
 
 Lifted ([§11.4.8](expressions.md#1148-lifted-operators)) forms of the unlifted predefined range operator defined above are also predefined.
 
 > *Example*: The following example uses array and string indexable sequences:
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+=======
+>>>>>>> 50008cc (add indexers and ranges)
 > ```csharp
 > string[] seasons = new string[] { "Summer", "Autumn", "Winter", "Spring" };
 > seasons[1..3]     // string[2] "Autumn", "Winter"
 > seasons[^2..^1]   // string[1] "Winter"
 > seasons[2..]      // string[2] "Winter", "Spring"
 > seasons[1..1]     // string[0]
+<<<<<<< HEAD
 >
+=======
+> 
+>>>>>>> 50008cc (add indexers and ranges)
 > string s2 = "Hello!";
 > Index? startN = 1;
 > Index? endN = ^2;
 > Range? r = startN .. endN;
 > s2[r.Value]        // OK: "ell"
 > ```
+<<<<<<< HEAD
 >
 > *end example*
 
 >>>>>>> 76616f9 (fix formatting)
+=======
+> *end example*
+
+>>>>>>> 50008cc (add indexers and ranges)
 ## 11.9 Arithmetic operators
 
 ### 11.9.1 General
@@ -3419,10 +3443,10 @@ The `*`, `/`, `%`, `+`, and `–` operators are called the arithmetic operators.
 
 ```ANTLR
 multiplicative_expression
-    : unary_expression
-    | multiplicative_expression '*' unary_expression
-    | multiplicative_expression '/' unary_expression
-    | multiplicative_expression '%' unary_expression
+    : range_expression
+    | multiplicative_expression '*' range_expression
+    | multiplicative_expression '/' range_expression
+    | multiplicative_expression '%' range_expression
     ;
 
 additive_expression