Define the parsing rules.

proglangclass · Dec 10, 2013 · c325a1e · c325a1e
1 parent 3cbb7cd
commit c325a1e
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diff --git a/grammar.y b/grammar.y
@@ -15,9 +15,136 @@ token IDENTIFIER
 token CONSTANT
 token END
 
+# Precedence table
+# Based on http://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B#Operator_precedence
+prechigh
+  left  '.'
+  right '!'
+  left  '*' '/'
+  left  '+' '-'
+  left  '>' '>=' '<' '<='
+  left  '==' '!='
+  left  '&&'
+  left  '||'
+  right '='
+  left  ','
+preclow
+
 rule
+  # All rules are declared in this format:
+  #
+  #   RuleName:
+  #     OtherRule TOKEN AnotherRule    { code to run when this matches }
+  #   | OtherRule                      { ... }
+  #   ;
+  #
+  # In the code section (inside the {...} on the right):
+  # - Assign to "result" the value returned by the rule.
+  # - Use val[index of expression] to reference expressions on the left.
+
+  Expressions:
+    Expression                          { result = Nodes.new([ val[0] ]) }
+  | Expressions Terminator Expression   { result = val[0] << val[2] }
+  |                                     { result = Nodes.new([]) }
+  | Expressions Terminator              { result = val[0] }
+  ;
+
+  Terminator:
+    NEWLINE
+  | ";"
+  ;
+
+  Expression:
+    Literal
+  | Call
+  | Operator
+  | GetConstant
+  | GetLocal
+  | SetLocal
+  | Def
+  | Class
+  | '(' Expression ')'            { result = val[1] }
+  ;
+
+  Literal:  
+    NUMBER              { result = NumberNode.new(val[0]) }
+  | STRING              { result = StringNode.new(val[0]) }
+  | TRUE                { result = TrueNode.new }
+  | FALSE               { result = FalseNode.new }
+  | NIL                 { result = NilNode.new }
+  ;
+
+  Call:
+    # method(1, 2, 3)
+    IDENTIFIER "(" Arguments ")"      { result = CallNode.new(nil, val[0], val[2]) }
+    # receiver.method(1, 2, 3)
+  | Expression "."
+    IDENTIFIER "(" Arguments ")"      { result = CallNode.new(val[0], val[2], val[4]) }
+  | Expression "." IDENTIFIER         { result = CallNode.new(val[0], val[2], []) }
+  ;
+
+  Arguments:
+    Expression                        { result = [ val[0] ] }
+  | Arguments "," Expression          { result = val[0] << val[2] }
+  |                                   { result = [] }
+  ;
+
+  Operator:
+  # 1 + 2 => 1.+(2)
+  # Binary operators
+    Expression '||' Expression    { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '&&' Expression    { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '==' Expression    { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '!=' Expression    { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '>' Expression     { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '>=' Expression    { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '<' Expression     { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '<=' Expression    { result = CallNode.new(val[0], val[1], [val[2]]) }
+    # 1 + 2 => 1.+(2)
+    #   1       +       2                                   1       "+"      [2]
+  | Expression '+' Expression     { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '-' Expression     { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '*' Expression     { result = CallNode.new(val[0], val[1], [val[2]]) }
+  | Expression '/' Expression     { result = CallNode.new(val[0], val[1], [val[2]]) }
+  # Unary operators
+  | '!' Expression                { result = CallNode.new(val[1], val[0], []) }
+  ;
+
+  # Local variables
+  GetLocal:
+    IDENTIFIER                    { result = GetLocalNode.new(val[0]) }
+  ;
+  SetLocal:
+    IDENTIFIER "=" Expression     { result = SetLocalNode.new(val[0], val[2]) }
+  ;  
+
+  # Method definition
+  Def:
+    DEF IDENTIFIER "(" Parameters ")" Terminator
+      Expressions
+    END                           { result = DefNode.new(val[1], val[3], val[6]) }
+  | DEF IDENTIFIER Terminator
+      Expressions
+    END                           { result = DefNode.new(val[1], [], val[3]) }
+  ;
+
+  Parameters:
+    IDENTIFIER                    { result = [ val[0] ] }
+  | Parameters "," IDENTIFIER     { result = val[0] << val[2] }
+  |                               { result = [] }
+  ;
 
+  # Class definition
+  Class:
+    CLASS CONSTANT Terminator
+      Expressions
+    END                           { result = ClassNode.new(val[1], val[3]) }
+  ;
 
+  # Retrieving the value of a constant
+  GetConstant:
+    CONSTANT                      { result = GetConstantNode.new(val[0]) }
+  ;
 end
 
 ---- header
@@ -33,4 +160,4 @@ end
 
   def next_token
     @tokens.shift
-  end
+  end