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require "readline"
require "types"
require "reader"
require "printer"
require "env"
# read
def READ(str)
return read_str(str)
end
# eval
def eval_ast(ast, env)
return case ast
when Symbol
env.get(ast)
when List
List.new ast.map{|a| EVAL(a, env)}
when Vector
Vector.new ast.map{|a| EVAL(a, env)}
else
ast
end
end
def EVAL(ast, env)
if not ast.is_a? List
return eval_ast(ast, env)
end
# apply list
a0,a1,a2,a3 = ast
case a0
when :def!
return env.set(a1, EVAL(a2, env))
when :"let*"
let_env = Env.new(env)
a1.each_slice(2) do |a,e|
let_env.set(a, EVAL(e, let_env))
end
return EVAL(a2, let_env)
else
el = eval_ast(ast, env)
f = el[0]
return f[*el.drop(1)]
end
end
# print
def PRINT(exp)
return _pr_str(exp, true)
end
# repl
repl_env = Env.new
REP = lambda {|str| PRINT(EVAL(READ(str), repl_env)) }
_ref = lambda {|k,v| repl_env.set(k, v) }
_ref[:+, lambda {|a,b| a + b}]
_ref[:-, lambda {|a,b| a - b}]
_ref[:*, lambda {|a,b| a * b}]
_ref[:/, lambda {|a,b| a / b}]
while line = Readline.readline("user> ", true)
begin
puts REP[line]
rescue Exception => e
puts "Error: #{e}"
puts "\t#{e.backtrace.join("\n\t")}"
end
end
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