EOI: Lecture 8 complete

App/EoI/Scripts/Eva.gd

@@ -31,7 +31,8 @@ func _init(parent, evalOut):
 	Parent  = parent
 
 func eval( ast ):
-	if ast.type() == NType.program :
+	match ast.type():
+		NType.program :
 			var   index = 1;
 			while index < ast.num_args():
 				eval( ast.arg(index) )
@@ -43,10 +44,29 @@ func eval( ast ):
 			else:
 				return null
 	
-	elif ast.type() == NType.block :
+		NType.block :
 			return eval_Block( ast )
 
-	elif ast.type() == NType.identifier :
+		NType.conditional:
+			var condition = eval( ast.arg(1) )
+
+			if condition:
+				# consequent
+				return eval( ast.arg(2) )
+			
+			# Alternate
+			if ast.num_args() > 2:
+				return eval( ast.arg(3))
+				
+		NType.expr_While:
+			var result
+			
+			while eval( ast.arg(1) ):
+				result = eval( ast.arg(2) )
+				
+			return result
+	
+		NType.identifier :
 			var identifier = ast.arg(1)
 		
 			if Parent != null && !Env.has( identifier):
@@ -54,10 +74,7 @@ func eval( ast ):
 		
 			return Env.lookup( identifier )
 		
-	elif ast.type() == NType.fn_Print :
+		NType.op_Assign :
-		return eval_Print( ast )
-		
-	elif ast.type() == NType.op_Assign :
 			var symbol = ast.arg(1)
 			var value  = eval( ast.arg(2) )
 			
@@ -66,14 +83,29 @@ func eval( ast ):
 			
 			return Env.set( symbol, value )
 
-	elif ast.type() == NType.variable :
+		NType.op_Greater:
+			return eval( ast.arg(1) ) > eval( ast.arg(2) )
+
+		NType.op_Lesser:
+			return eval( ast.arg(1) ) < eval( ast.arg(2) )
+
+		NType.op_GreaterEqual:
+			return eval( ast.arg(1) ) >= eval( ast.arg(2) )
+
+		NType.op_LesserEqual:
+			return eval( ast.arg(1) ) <= eval( ast.arg(2) )
+			
+		NType.fn_Print :
+			return eval_Print( ast )
+	
+		NType.variable :
 			var symbol = ast.arg(1)
 			var value  = eval( ast.arg(2) )
 
 			Env.define_Var(symbol, value)
 			return value
 	
-	elif ast.is_Number() : 	
+	if ast.is_Number() : 	
 		return float( ast.arg(1) )		
 	
 	elif ast.is_String() : 
@@ -81,10 +113,6 @@ func eval( ast ):
 		
 	return eval_Numeric( ast )
 
-	var msgT = "eval - Unimplemented: {ast}"
-	var msg  = msgT.format({"ast" : JSON.print(ast.to_SExpression(), "\t") })
-	throw(msg)
-
 func eval_Block( ast ):
 	var eva_Block = get_script().new( self, EvalOut )
 	
@@ -134,6 +162,10 @@ func eval_Numeric( ast ):
 			
 		return result
 			
+	var msgT = "eval - Unimplemented: {ast}"
+	var msg  = msgT.format({"ast" : JSON.print(ast.to_SExpression(), "\t") })
+	throw(msg)
+		
 func eval_Print( ast ):
 	EvalOut.text += "\n" + String( eval( ast.arg(1) ) )
 	return null

App/EoI/Scripts/Lexer.gd

@@ -27,13 +27,16 @@ const TType : Dictionary = \
 	def_Block = "Expression Block Start",
 	def_Start = "Expression Start",
 	def_End   = "Expression End",
-	def_Var   = "Variable",
+	def_Cond  = "Expression Conditional",
+	def_While = "Expression While",
+	def_Var   = "Variable Declaration",
 	
 	literal_Number = "Literal: Number",
 	literal_String = "Literal: String",
 	
 	op_Assgin     = "Assignment",
 	op_Numeric    = "op_Numeric",
+	op_Relational = "op_Relational",
 	
 	fn_Print = "Print",
 	
@@ -50,6 +53,8 @@ const Spec : Dictionary = \
 	TType.def_Block : "start \"begin\"",
 	TType.def_Start : "start \\(",
 	TType.def_End   : "start \\)",
+	TType.def_Cond  : "start \"if\"",
+	TType.def_While : "start \"while\"",
 	TType.def_Var   : "start \"var\"",
 	
 	TType.literal_Number : \
@@ -62,6 +67,7 @@ const Spec : Dictionary = \
 	
 	TType.op_Assgin     : "start \"set\"",
 	TType.op_Numeric    : "start set(+ \\- * /)",
+	TType.op_Relational : "start set(> <) =.repeat(0-1)",
 	
 	TType.fn_Print : "start \"print\"",
 	

App/EoI/Scripts/Parser.gd

@@ -23,6 +23,9 @@ const NType = \
 	
 	block = "Scope Block",
 
+	conditional = "Conditional",
+	expr_While  = "Expression While",
+
 	literal_Number = "Literal: Number",
 	literal_String = "Literal: String",
 	
@@ -33,6 +36,11 @@ const NType = \
 	op_Mult    = "*",
 	op_Div     = "/",
 	
+	op_Greater      = ">",
+	op_GreaterEqual = ">=",
+	op_Lesser       = "<",
+	op_LesserEqual  = "<=",
+	
 	fn_Print = "Print",
 
 	identifier = "Identifier",
@@ -149,6 +157,10 @@ func parse_Expression():
 	match NextToken.Type :
 		TType.def_Block:
 			node = parse_Block()
+		TType.def_Cond:
+			node = parse_ConditionalIf()
+		TType.def_While:
+			node = parse_While()
 		TType.def_Var:
 			node = parse_Variable()
 		TType.fn_Print:
@@ -157,6 +169,9 @@ func parse_Expression():
 			node = parse_op_Assign()
 		TType.op_Numeric:
 			node = parse_op_Numeric()
+		TType.op_Relational:
+			node = parse_op_Relational()
+
 	
 	var arg = 1
 	while NextToken.Type != TType.def_End:
@@ -179,6 +194,20 @@ func parse_Block():
 
 	return node
 	
+func parse_ConditionalIf():
+	var \
+	node = ASTNode.new()
+	node.set_Type(NType.conditional)
+	eat(TType.def_Cond)
+	return node
+	
+func parse_While():
+	var \
+	node = ASTNode.new()
+	node.set_Type(NType.expr_While)
+	eat(TType.def_While)
+	return node
+	
 func parse_Variable():
 	var \
 	node = ASTNode.new()
@@ -260,6 +289,23 @@ func parse_op_Numeric():
 	
 	return node
 	
+func parse_op_Relational():
+	var node = ASTNode.new()
+
+	match NextToken.Value:
+		NType.op_Greater:
+			node.set_Type(NType.op_Greater)
+		NType.op_Lesser:
+			node.set_Type(NType.op_Lesser)
+		NType.op_GreaterEqual:
+			node.set_Type(NType.op_GreaterEqual)
+		NType.op_LesserEqual:
+			node.set_Type(NType.op_LesserEqual)
+
+	eat(TType.op_Relational)
+
+	return node
+	
 func parse_Literal():
 	var node = ASTNode.new()
 	
@@ -283,3 +329,4 @@ func _init(lexer, errorOut) :
 	Lexer    = lexer
 	
 	NextToken = Lexer.next_Token()
+