class Conditional extends Statement:
# Expression test; Statement then_branch, else_branch
# else_branch == null means "if... then"
test
then_branch
else_branch
function Conditional(t, tb, eb = None)
this.test = t
this.then_branch = tb
if eb is None:
this.else_branch = new Skip()
else:
this.else_branch = eb
function to_string():
# Гишүүдээр нь тайлбарласан хэвлэх функц
class Operator:
val
function Operator(s):
this.val = s
class Binary extends Expression:
function Binary(o, left, right):
this.op = o
this.term1 = left
this.term2 = right
function to_string():
# Гишүүдээ хүнд ойлгомжтойгоор хэвлэх
class Unary extends Expression:
function Unary(o, e):
this.op = o
this.term = e
function to_string():
...
class BoolValue extends Value:
boolean value
function BoolValue (v = None):
if v is None:
this.value = False
else:
this.value = v
this.undef = False
class CharValue extends Value:
char value = ' '
...
class FloatValue extends Value:
float value = 0.0
...
class Parser
...
function statement():
...
else if this.current_token is If:
s = this.if_statement()
...
function if_statement():
this.current_token = this.lexer.next_token()
this.match(Left_Paren)
t = this.expression()
this.match(Right_Paren)
s = this.statement()
if this.current_token is Else:
this.current_token = this.lexer.next_token()
return Conditional(t, s, this.statement())
return Conditional(t, s)
function expression():
e = this.conjunction()
while this.current_token is Or:
op = Operator(this.current_token.value)
term1 = e
this.current_token = this.lexer.next_token()
term2 = this.conjunction()
e = Binary(op, term1, term2)
return e
function conjunction():
e = this.equality()
while this.current_token is And:
op = Operator(this.current_token.value)
this.current_token = this.lexer.next_token()
term2 = this.equality()
binary = Binary(op, e, term2)
e = binary
return e
function equality():
e = this.relation()
while this.current_token is Equals|Not_Equals:
op = Operator(this.current_token.value)
this.current_token = this.lexer.next_token()
term2 = this.relation()
e = Binary(op, e, term2)
return e
function relation()
e = this.addition()
while this.current_token is Less|Less_Equal|Greater|Greater_Equal:
op = Operator(this.current_token.value)
this.current_token = this.lexer.next_token()
term2 = this.addition()
e = Binary(op, e, term2)
return e
function addition():
e = this.term()
while this.current_token is Plus|Minus:
op = Operator(this.current_token.type)
term2 = this.term()
e = Binary(op, e, term2)
return e
function term():
e = this.factor()
while this.current_token is Multiply|Divide:
op = Operator(this.current_token.value)
term2 = this.factor()
e = Binary(op, e, term2)
return e
function factor():
if this.current_token is Not|Minus:
op = Operator(this.current_token.value)
term = this.primary()
return Unary(op, term)
else:
return this.primary()
function primary():
e = None
if this.current_token is Identifier:
e = Variable(this.current_token.value)
else if this.current_token is IntLiteral|BoolLiteral|FloatLiteral| CharLiteral:
e = this.literal()
else if this.current_token is Left_Paren:
this.current_token = this.lexer.next_token()
e = this.expression()
this.match(Right_Paren)
else if this.current_token is Int|Char|Float|Bool:
op = Operator(this.current_token.value)
this.match(Left_Paren)
term = this.expression()
this.match(Right_Paren)
e = Unary(op, term)
else:
print "Sum Ting Wong"
sys.exit()
return e
function literal():
if this.current_token.type is Int:
s = this.match(TokenType.INT_LITERAL)
return IntValue(int(s))
else if this.current_token.type is Char:
s = this.match(TokenType.CHAR_LITERAL)
return CharValues(s[0])
else if this.current_token.type is True:
s = this.match(TokenType.TRUE)
return BoolValue(true)
else if this.current_token.type is False:
s = this.match(TokenType.FALSE)
return BoolValue(false)
else if this.current_token is Float:
s = this.match(TokenType.FLOAT_LITERAL)
return FloatValue(float(s))
throw "Энд хүрэх ёсгүй байсан"
