华为笔试9月20日100+100+90

机试前两题不难，第三题坑好多，最后也没AK

做了个比较简洁的实现，用python的locals()+eval()，其实可以很好处理加减乘除。

import sys
d = locals()
for line in sys.stdin:
    line = line.strip().replace("/", "//")
    if line.startswith("let "):
        t = line[4:].split(" = ")
        if len(t) != 2 or not t[0].isidentifier():
            print("<syntax-error>")
        else:
            name, expr = t
            try:
                # d[name] = eval(expr)
                l = expr.split()
                while len(l) > 1:
                    x = eval(" ".join(l[:3]))
                    l = [str(x)] + l[3:]
                d[name] = int(l[0])
            except NameError:
                d[name] = "UNDEF"
            except:
                print("<syntax-error>")
    elif line.startswith("out(") and line.endswith(")"):
        name = line[4:-1]
        if not name.isidentifier():
            print("<syntax-error>")
        elif name not in d or d[name] == "UNDEF":
            print("<undefined>")
        elif d[name] < -2147483648:
            print("<underflow>")
        elif d[name] > 2147483647:
            print("<overflow>")
        else:
            print(d[name])
    else:
        print("<syntax-error>")