def parse_let_family(tp: ast.Tuple) -> ast.Node:
if len(tp.elements) < 3:
raise ParseError(
f'{tp.elements[0]}: bad syntax, no expression in body')
elem = tp.elements[1]
if not isinstance(elem, ast.Tuple):
raise ParseError(
f'{tp.elements[0]}: bad syntax, expected bindings, given: {elem}')
bindings: List[Node] = elem.elements
patterns: List[ast.Name] = []
exprs: List[Node] = []
for i, binding in enumerate(bindings):
if isinstance(binding, ast.Tuple):
if len(binding.elements) == 2:
if isinstance(binding.elements[0], ast.Name):
patterns.append(binding.elements[0])
exprs.append(parse_node(binding.elements[1]))
continue
raise ParseError(
f'{tp.elements[0]}: bad syntax, not an identifer and expression for a binding {binding}'
)
body = ast.Block(parse_list(tp.elements[2:]))
name = tp.elements[0]
if not isinstance(name, ast.Name):
raise ParseError(f'expected a Name, given {name}')
if name.identifier == constants.LET:
return ast.Let(patterns, exprs, body)
elif name.identifier == constants.LET_STAR:
return ast.LetStar(patterns, exprs, body)
elif name.identifier == constants.LET_REC:
return ast.LetRec(patterns, exprs, body)
else:
raise ParseError(f'{tp.elements[0]}: should not be here')
def let(self):
self.lexer.match("let")
name = self.lexer.match_type(TokenType.Ident)
self.lexer.match("=")
value = self.expr()
return ast.Let(name, value)
def p_inner_lets_initialized(self, parse):
'''
nested_lets : ID COLON TYPE ASSIGN expression IN expression
| nested_lets COMMA ID COLON TYPE ASSIGN expression
'''
parse[0] = AST.Let(instance=parse[1],
return_type=parse[3],
expression=parse[5],
body=parse[7])
def p_inner_lets_simple(self, parse):
'''
nested_lets : ID COLON TYPE IN expression
| nested_lets COMMA ID COLON TYPE
'''
parse[0] = AST.Let(instance=parse[1],
return_type=parse[3],
expression=None,
body=parse[5])
def p_expression_let_initialized(self, parse):
'''
let_expression : LET ID COLON TYPE ASSIGN expression IN expression
| nested_lets COMMA LET ID COLON TYPE ASSIGN expression
'''
parse[0] = AST.Let(instance=parse[2],
return_type=parse[4],
expression=parse[6],
body=parse[8])
def p_expression_let_simple(self, parse):
'''
let_expression : LET ID COLON TYPE IN expression
| nested_lets COMMA LET ID COLON TYPE
'''
parse[0] = AST.Let(instance=parse[2],
return_type=parse[4],
expression=None,
body=parse[6])
def let_stmt(self) -> ast.Let:
toks = TokenList()
toks.add(self.peek()) # Add 'let' token itself for correct begin
var_names, var_types = self.let_lhs() # Writes variable names to symbol table
if not toks.add(self.match(token.ASSIGN)):
raise ParseException("Empty let statements are not supported. Always assign a value!")
expr : typing.Union[ast.ExpressionList, ast.AssignOp] = self.assignment()
toks.add(self.match(token.SEMICOLON))
return ast.Let(toks, var_names, var_types, expr, self.symbol_tree.take_snapshot())
def parse_let(self, token, frame):
"""Parse Let expression"""
if len(frame) < 2:
_malformed(token)
# Resolve first as return val versus args
letres = None
letargs = None
letexpr = None
if isinstance(frame[0], ast.Symbol):
letres = frame.pop(0)
else:
sp = token.getsourcepos()
lsym = "let_" + str(sp.lineno) + "_" + str(sp.colno)
letres = ast.Symbol(lsym,
Token("LET_RES", lsym, token.getsourcepos()),
self.input)
if isinstance(frame[0], ast.CollectionAst):
letargs = frame.pop(0)
else:
_panic(
"{}:{} Let expects local argument pair(s) signature [...] {}",
token)
if letargs.ctype != CollTypes.LIST:
_panic(
"{}:{} Invalid let argument pair(s) type. Should be [...] {}",
token)
if len(frame) < 1:
_panic("{}:{} Missing Let expression {}", token)
letexpr = [frame.pop(0)]
letargs = ast.LetPairs(letargs, token, self.input)
_check_no_declarations(token, letexpr, self._decl_set)
frame.insert(0, ast.Let(letres, letargs, letexpr, token, self.input))
return frame
def p_expression_let_list(self, parse):
"""
let_expression : LET formal_list IN expression
"""
parse[0] = AST.Let(declarations=parse[2], body=parse[4])
def statement(self):
if self.match("let"):
line = self.pop().line
ty = self.type()
if self.match_val("="):
name = ty[1]
ty = None
#this is where more complete type parsing would happen
#for the time being, just error out
elif self.match("ident"):
name = self.pop().val
else:
raise ValueError(
f"expected type in var declaration on line {line}, saw {self.tl[0].val}"
)
self.consume(
"=",
f"expected '=' in let declaration on line {line}, saw {self.tl[0].val}"
)
ex = self.expr()
if ty != None:
return ast.Let(name, (ty, None), ex)
else:
return ast.Let(name, None, ex)
elif self.match("var"):
line = self.pop().line
ty = self.type()
if self.match_val("="):
name = ty[0]
ty = None
#this is where more complete type parsing would happen
#for the time being, just error out
elif self.match("ident"):
name = self.pop().val
else:
raise ValueError(
f"expected type in var declaration on line {line}, saw {self.tl[0].val}"
)
self.consume(
"=",
f"expected '=' in var declaration on line {line}, saw {self.tl[0].val}"
)
ex = self.expr()
return ast.Var(name, ty, ex)
elif self.match("if"):
line = self.pop().line
ex = self.expr()
thenstmnts = self.statementlist("if statement", line)
if not self.match("else"):
elsestmnts = None
else:
line = self.pop().line
elsestmnts = self.statementlist("else statement", line)
return ast.If(ex, thenstmnts, elsestmnts)
elif self.match('return'):
self.pop()
returning = self.expr()
return ast.Return(returning)
elif self.match('while'):
line = self.pop().line
condition = self.expr()
body = self.statementlist("while body", line)
return ast.While(condition, body)
else:
lhs = self.expr()
if self.match_val('=') or self.match_val('+=') or self.match_val(
'-=') or self.match_val('*=') or self.match_val(
'/=') or self.match_val('%='):
op = self.pop().val
rhs = self.expr()
if (op[0] != '='):
rhs = ast.Binary(lhs, op[0], rhs)
return ast.Assign(lhs, rhs)
else:
return lhs