errors.rb in wlang-0.9.1

- old
+ new
@@ -1,16 +1,80 @@
 module WLang
   
   # Main error of all WLang errors.
-  class Error < StandardError; end
+  class Error < StandardError
+    
+    # The parser state whe this error has been raised
+    attr_accessor :parser_state
+    
+    # Optional cause (other lower level exception)
+    attr_accessor :cause
+    
+    # Creates an error instance with a given parser state
+    def initialize(msg = nil, parser_state = nil, cause = nil)
+      raise ArgumentError, "msg expected to be nil or a String" unless (msg.nil? or String===msg)
+      raise ArgumentError, "parser_state expected to be nil or a State"\
+        unless (parser_state.nil? or ::WLang::Parser::State===parser_state)
+      super(msg)
+      @parser_state = parser_state
+      @cause = cause
+    end
+    
+    # Returns a friendly wlang backtrace
+    def wlang_backtrace
+      parser_state ? parser_state.backtrace : ["no backtrace information, sorry"]
+    end
+    
+  end # class Error
   
-  # Raise when something fails when evaluting through the parser context
-  class EvalError < StandardError; end
+  #
+  # Raised by hosted languages when something fails during 
+  # evaluation.
+  #
+  class EvalError < ::WLang::Error
+    
+    # The expression whose evaluation failed
+    attr_accessor :expression
+    
+    # Creates an error instance with an optional expression that
+    # failed
+    def initialize(msg = nil, parser_state = nil, expression = nil, cause = nil)
+      super(msg, parser_state, cause)
+      @expression = expression
+    end
+    
+    def to_s
+      "Evaluation of #{@expression} failed, #{@cause ? @cause.message : ''}"
+    end
+    
+  end # class EvalError
   
+  #
+  # Raised when a variable may not be found in the current 
+  # parser scope
+  #
+  class UndefinedVariableError < ::WLang::EvalError
+    
+    # Name of the variable that could not be found
+    attr_accessor :variable
+    
+    # Creates an error instance with an optional variable name
+    def initialize(msg = nil, parser_state = nil, expression = nil, variable = nil)
+      super(msg, parser_state, expression)
+      @variable = variable
+    end
+    
+    def to_s
+      "Unable to find variable #{@variable}"
+    end
+    
+  end # class UndefinedVariableError
+  
   # Error raised by a WLang parser instanciation when an error occurs. 
-  class ParseError < StandardError;  
+  class ParseError < ::WLang::Error
     
+    # Where did the parsing failed
     attr_accessor :line, :column
     
-  end
+  end # class ParseError
   
-end # module WLang
+end # module WLang
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