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--- step2_eval ----------------------------------
import types, reader, printer
READ(str): return reader.read_str(str)
eval_ast(ast,env):
switch type(ast):
symbol: return lookup(env, ast) OR raise "'" + ast + "' not found"
list,vector: return ast.map((x) -> EVAL(x,env))
hash: return ast.map((k,v) -> list(k, EVAL(v,env)))
_default_: return ast
EVAL(ast,env):
if not list?(ast): return eval_ast(ast, env)
f, args = eval_ast(ast, env)
return apply(f, args)
PRINT(exp): return printer.pr_str(exp)
repl_env = {'+: add_fn, ...}
rep(str): return PRINT(EVAL(READ(str),repl_env))
main loop:
try: println(rep(readline("user> ")))
catch e: println("Error: ", e)
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