python.2/step1_read_print.py

   1 import readline
   2
   3 import reader
   4 from mal_types import MalExpression, MalSyntaxException
   5
   6
   7 def READ(x: str) -> MalExpression:
   8     return reader.read(x)
   9
  10
  11 def EVAL(x: MalExpression) -> MalExpression:
  12     return x
  13
  14
  15 def PRINT(x: MalExpression) -> str:
  16     return str(x)
  17
  18
  19 def rep(x: str) -> str:
  20     try:
  21         return PRINT(EVAL(READ(x)))
  22     except BaseException:
  23         return "Expression is invalid or unbalanced: " + x
  24
  25
  26 if __name__ == "__main__":
  27     # repl loop
  28     eof: bool = False
  29     while not eof:
  30         try:
  31             line = input("user> ")
  32             readline.add_history(line)
  33             try:
  34                 print(rep(line))
  35             except MalSyntaxException as e:
  36                 print("ERROR: invalid syntax: " + str(e))
  37         except EOFError:
  38             eof = True