def interpret_fourcode_read(code):
"""(READ, None, None, VAR)"""
id, isarr = get_id(code[3])
symbol = get_symbol_in_table(id)
symbol.declare_line = code.line
i = input()
if i.startswith('"') and i.startswith('"'): # 输入为字符串
if symbol.type != 'string':
raise RunningError(
'Line %d: should input a number to a number variable %s' %
(code.line, symbol.name))
if isarr:
index = is_index_valid(symbol, isarr)
symbol.arr[index] = i
else:
symbol.value = i
elif is_num(i):
if symbol.type == 'string':
raise RunningError(
'Line %d: should input a string to a string variable %s' %
(code.line, symbol.name))
value = eval(i) * 1.0 if symbol.type == 'float' else int(eval(i))
if isarr:
index = is_index_valid(symbol, isarr)
symbol.arr[index] = value
else:
symbol.value = value
else:
raise RunningError('Line %d: input is invalid' % code.line)
def interpret_fourcode(code):
"""四元式核心主函数，遇到错误则记录并跳到下一条四元式"""
global cur_code, level_count
try:
type = code[0]
if type == 'JMP':
if code[1] is None or not get_symbol_in_table(code[1]).value:
cur_code = code[3] - 1
return
elif type == 'IN':
level_count += 1
elif type == 'OUT':
level_count -= 1
elif type == 'READ':
interpret_fourcode_read(code)
elif type == 'WRITE':
interpret_fourcode_write(code)
elif type == 'ASSIGN':
interpret_fourcode_assign(code)
elif type in ['int', 'float', 'string']:
interpret_fourcode_declare(code)
else:
interpret_fourcode_op(code)
except Exception as e:
skip_exception(RunningError, e)
finally:
cur_code += 1
def is_index_valid(symbol, index):
"""检查四元式中数组的下标是否合法，合法则返回实际的下标值"""
if match(r'\d+', index):
value = eval(index)
if value < len(symbol.arr): #判断数组是否越界
return value
else:
raise RunningError(
'Line %d: index %d out of bound in variable %s' %
(symbol.declare_line, value, symbol.name))
else:
index_symbol = get_symbol_in_table(index)
if index_symbol.type in ['NUM', 'int', 'float', 'temp']:
if int(index_symbol.value) != index_symbol.value: #判断下标是否为整数
raise RunningError(
'Line %d: index %s of variable %s is float point number' %
(symbol.declare_line, index_symbol.value, symbol.name))
if -1 < index_symbol.value < len(symbol.arr): #判断数组是否越界
return int(index_symbol.value)
else:
raise RunningError(
'Line %d: index %s out of bound in variable %s' %
(symbol.declare_line, str(
index_symbol.value), symbol.name))
else:
raise RunningError(
'Line %d: variable %s\'s index should be a non-negetive integer'
% (symbol.declare_line, symbol.name))
def get_var_value(varname):
"""传入一个变量名a或带下标的变量a[i]，返回该变量对应的符号和其值"""
id, isarr = get_id(varname)
symbol = get_symbol_in_table(id)
value = symbol.arr[is_index_valid(symbol,
isarr)] if isarr else symbol.value
return symbol, value
def interpret_fourcode_op(code):
"""(OP, left, right|None, result)"""
op = code[0]
v1, v2 = get_value(code[1]), get_value(code[2])
if type(v1) == str or type(v2) == str:
raise RunningError('Line %d: string cannot in expression!' % code.line)
value = None
if op == '!':
value = not v1 #逻辑取反
elif op == '-':
if v2 is None: value = -v1 #取负数
else: value = eval(str(v1) + '-' + str(v2))
elif op == '/':
if v2 == 0:
raise RunningError('Line %d: divisor cannot be zero!' % code.line)
value = v1 / v2
elif op == '&&':
if not v1: value = False # 考虑短路运算
else: value = v2
elif op == '||':
if v1: value = True
else: value = v2
elif op == '<>':
value = v1 != v2
else:
value = eval(str(v1) + op + str(v2))
symbol = get_symbol_in_table(code[3])
symbol.value = value
def interpret_fourcode_assign(code):
"""(ASSIGN, VAR, 0/1, STR/VAR/NUM)"""
to_id, to_isarr = get_id(code[1])
to_symbol = get_symbol_in_table(to_id)
if code[2]: #赋值内容为变量的值
from_symbol, value = get_var_value(code[3])
else: #直接将四元式第四项的内容赋给变量
value = code[3]
if is_num(str(value)) and to_symbol.type == 'string':
raise RunningError('Line %d: not match type in assignment statement' %
code.line)
if to_symbol.type == 'int': value = int(value)
if to_isarr:
to_symbol.declare_line = code.line
to_index = is_index_valid(to_symbol, to_isarr)
to_symbol.arr[to_index] = value
else:
to_symbol.value = value