[jackhill/mal.git] / process / step2_eval.txt

--- 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)
    if empty?(ast): return ast
    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)
Commit	Line	Data
f5223195 JM	1	--- step2_eval ----------------------------------
	2	import types, reader, printer
	3
	4	READ(str): return reader.read_str(str)
	5
	6	eval_ast(ast,env):
	7	switch type(ast):
	8	symbol: return lookup(env, ast) OR raise "'" + ast + "' not found"
	9	list,vector: return ast.map((x) -> EVAL(x,env))
	10	hash: return ast.map((k,v) -> list(k, EVAL(v,env)))
	11	_default_: return ast
	12
	13	EVAL(ast,env):
	14	if not list?(ast): return eval_ast(ast, env)
1af7aff1	15	if empty?(ast): return ast
f5223195 JM	16	f, args = eval_ast(ast, env)
	17	return apply(f, args)
	18
	19	PRINT(exp): return printer.pr_str(exp)
	20
	21	repl_env = {'+: add_fn, ...}
	22	rep(str): return PRINT(EVAL(READ(str),repl_env))
	23
	24	main loop:
	25	try: println(rep(readline("user> ")))
	26	catch e: println("Error: ", e)