From 5f78969d4a71908fd8ae43c886614ef0e5664eb0 Mon Sep 17 00:00:00 2001
From: Melody Horn <melody@boringcactus.com>
Date: Mon, 2 Nov 2020 20:52:52 -0700
Subject: define switch statement
---
language/statements/index.rst | 2 +-
language/statements/structure.rst | 20 ++++++++++++++++++++
syntax.md | 9 ---------
3 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/language/statements/index.rst b/language/statements/index.rst
index 38bfbb1..e0a0a37 100644
--- a/language/statements/index.rst
+++ b/language/statements/index.rst
@@ -12,7 +12,7 @@ Statements
When a block is executed, each of the containing statements, in linear order, is executed.
-.. crowbar:element:: Statement <- VariableDefinition / StructureStatement / FlowControlStatement / AssignmentStatement / FragileStatement / ExpressionStatement
+.. crowbar:element:: Statement <- VariableDefinition / StructureStatement / FlowControlStatement / AssignmentStatement / FragileStatement / ExpressionStatement / EmptyStatement
Crowbar has many different types of statement.
diff --git a/language/statements/structure.rst b/language/statements/structure.rst
index 9330bf6..1a412af 100644
--- a/language/statements/structure.rst
+++ b/language/statements/structure.rst
@@ -19,3 +19,23 @@ Structure Statements
First, the expression is evaluated.
If the expression evaluates to a ``bool`` value of ``true``, then the first block will be executed.
If the expression evaluates to a ``bool`` value of ``false``, either the second block is executed or nothing is executed.
+
+.. crowbar.element.. SwitchStatement <- 'switch' '(' Expression ')' '{' (CaseSpecifier / Statement)+ '}'
+ CaseSpecifier <- 'case' Expression ':' / 'default' ':'
+
+ A switch statement allows many different actions to be taken depending on the value of some expression.
+
+ Compile-time Behavior:
+
+ The expression must have a type which is either some integer type or an enum.
+ The expression in a case specifier must have a value which can always be known at compile time, i.e. its value must be a constant or computed from only constants.
+ Either there must be a case specifier for every valid value in the type of the switch expression, or there must be a default case specifier.
+ At most one default case may be present.
+
+ Runtime Behavior:
+
+ First, the switch expression is evaluated.
+ Whichever case specifier has the same value, or the default case specifier if none is found, is then selected as the matching case specifier.
+ Any case specifiers immediately following the matching case specifier is ignored.
+ Subsequent statements are then executed, in linear order, until another case specifier is reached.
+ The execution of the switch statement then ends.
diff --git a/syntax.md b/syntax.md
index b8e4554..74e5cc3 100644
--- a/syntax.md
+++ b/syntax.md
@@ -3,15 +3,6 @@
### Statements
```PEG
-IfStatement ← 'if' Expression Block 'else' Block /
- 'if' Expression Block
-
-SwitchStatement ← 'switch' Expression '{' SwitchCase+ '}'
-SwitchCase ← CaseSpecifier Block /
- 'default' Block
-CaseSpecifier ← 'case' Expression ',' CaseSpecifier /
- 'case' Expression ','?
-
WhileStatement ← 'while' Expression Block
DoWhileStatement ← 'do' Block 'while' Expression ';'
ForStatement ← 'for' VariableDefinition? ';' Expression ';' AssignmentStatementBody? Block
--
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