unexpected symbol、unexpected end of input
问题:
# 不是一个合法的表达式(expression)
parse(text = "2^")
parse(text = "2a")
# Unexpected symbol
解决:
parse(text = "2^2")
parse(text = "2*a")
完整错误:
Error in parse(text = "2a"): <text>:1:2: unex