def pr_str(entity, print_readably=True):
if isinstance(entity, MalException):
return f'{pr_str(entity.value)}'
if isinstance(entity, Exception):
return entity.args[0]
elif is_function(entity):
return '#function'
elif is_nil(entity):
return 'nil'
elif is_bool(entity):
return {
TRUE: 'true',
FALSE: 'false',
}[entity]
elif is_number(entity):
return str(entity)
elif is_symbol(entity):
return str(entity, 'utf-8')
elif is_keyword(entity):
return ':' + entity[1:]
elif is_string(entity):
if print_readably:
return '"' + entity.replace('\\', '\\\\').replace('"', '\\"').replace('\n', '\\n') + '"'
return entity
elif is_atom(entity):
return f'(atom {deref(entity)})'
elif is_list(entity):
return '(' + ' '.join(pr_str(inner, print_readably) for inner in entity) + ')'
elif is_vector(entity):
return '[' + ' '.join(pr_str(inner, print_readably) for inner in entity) + ']'
elif is_hashmap(entity):
return (
'{'
+ ' '.join(f'{pr_str(k, print_readably)} {pr_str(v, print_readably)}' for k, v in entity.items())
+ '}'
)
raise RuntimeError(f'pr_str: unknown type {type(entity)}')
def EVAL(ast, env):
"""
Evaluate set of mal instructions.
"""
while True:
if not is_list(ast):
return eval_ast(ast, env)
elif is_empty(ast):
return ast
else:
ast = macroexpand(ast, env)
if not is_list(ast):
return eval_ast(ast, env)
elif not ast:
return ast
if first(ast) == make_symbol('def!'):
try:
operands = rest(ast)
symbol = first(operands)
value = EVAL(first(rest(operands)), env)
except ValueError:
raise RuntimeError('def! syntax is (def! /symbol/ /value/)')
if is_nil(value):
return env.get(symbol)
env.set(symbol, value)
return value
elif first(ast) == make_symbol('let*'):
let_error = RuntimeError('let* syntax is (let* /list_of definitions/ /list_of_instructions/)') # noqa
new_env = Env(env)
try:
operands = rest(ast)
definitions, instructions = operands
except Exception:
raise let_error
if len(definitions) % 2 != 0:
raise let_error
symbol_value_pairs = list(zip(
definitions[0::2],
definitions[1::2],
))
for symb, value in symbol_value_pairs:
new_env.set(symb, EVAL(value, new_env))
ast = instructions
env = new_env
continue
elif first(ast) == make_symbol('if'):
elements = rest(ast)
condition = first(elements)
true_branch = first(rest(elements))
false_branch = first(rest(rest(elements)))
condition = EVAL(condition, env)
# empty lists, strings and 0 are 'truthy', only false and nil are 'falsy'
if is_nil(condition) or is_bool(condition) and condition == FALSE:
ast = false_branch
else:
ast = true_branch
continue
elif first(ast) == make_symbol('fn*'):
try:
op, binds, body = ast
except ValueError:
raise RuntimeError('fn* syntax us (fn* /arguments/ /function_body/)') # noqa
def closure(*arguments):
try:
new_env = Env(outer=env, binds=binds, exprs=arguments)
except ValueError:
raise RuntimeError(
'Error: function is called with wrong number of parameters'
f'expected: {len(binds)}, actual: {len(arguments)}'
)
return EVAL(body, new_env)
return make_function(body, binds, env, closure)
elif first(ast) == make_symbol('do'):
op, *exprs = ast
for expr in exprs[:-1]:
EVAL(expr, env)
ast = exprs[-1]
continue
# quoting element
elif ast[0] == make_symbol('quote'):
return ast[1]
elif ast[0] == make_symbol('quasiquote'):
ast = quasiquote(ast[1])
continue
elif ast[0] == make_symbol('defmacro!'):
try:
op, symbol, operation_ast = ast
fn_sym, binds, body = operation_ast
if fn_sym != make_symbol('fn*'):
raise ValueError
except ValueError:
raise RuntimeError('defmacro! syntax is (def! /symbol/ /function_body/)')
fn = make_function(body, binds, env, None, True) # fn.fn is set to None. Check in step 9 is it ok
env.set(symbol, fn)
return NIL
elif ast[0] == make_symbol('macroexpand'):
return macroexpand(ast[1], env)
elif ast[0] == make_symbol('try*'):
try:
op, try_branch, catch = ast
except ValueError:
op, try_branch = ast
return EVAL(try_branch, env)
try:
return EVAL(try_branch, env)
except Exception as exc:
catch_symbol, exception_symbol, catch_branch = catch
return EVAL(catch_branch, Env(env, [exception_symbol], [exc]))
func, *args = eval_ast(ast, env)
if not is_mal_function(func):
# core function
return func(*args)
ast = func.ast
env = Env(func.env, func.params, args)
def EVAL(ast, env):
"""
Evaluate set of mal instructions.
"""
while True:
if not is_list(ast):
return eval_ast(ast, env)
elif is_empty(ast):
return ast
elif first(ast) == make_symbol('def!'):
try:
operands = rest(ast)
symbol = first(operands)
value = EVAL(first(rest(operands)), env)
except ValueError:
raise RuntimeError('def! syntax is (def! /symbol/ /value/)')
env.set(symbol, value)
return value
elif first(ast) == make_symbol('let*'):
let_error = RuntimeError(
'let* syntax is (let* /list_of definitions/ /list_of_instructions/)'
) # noqa
new_env = Env(env)
try:
operands = rest(ast)
definitions, instructions = operands
except Exception:
raise let_error
if len(definitions) % 2 != 0:
raise let_error
symbol_value_pairs = list(
zip(
definitions[0::2],
definitions[1::2],
))
for symb, value in symbol_value_pairs:
new_env.set(symb, EVAL(value, new_env))
ast = instructions
env = new_env
continue
elif first(ast) == make_symbol('if'):
elements = rest(ast)
condition = first(elements)
true_branch = first(rest(elements))
false_branch = first(rest(rest(elements)))
condition = EVAL(condition, env)
# empty lists, strings and 0 are 'truthy', only false and nil are 'falsy'
if is_nil(condition) or is_bool(condition) and condition == FALSE:
ast = false_branch
else:
ast = true_branch
continue
elif first(ast) == make_symbol('fn*'):
try:
op, binds, body = ast
except ValueError:
raise RuntimeError(
'fn* syntax us (fn* /arguments/ /function_body/)') # noqa
def closure(*arguments):
try:
new_env = Env(outer=env, binds=binds, exprs=arguments)
except ValueError:
raise RuntimeError(
'Error: function is called with wrong number of parameters'
f'expected: {len(binds.value)}, actual: {len(arguments)}'
)
return EVAL(body, new_env)
return make_function(body, binds, env, closure)
elif first(ast) == make_symbol('do'):
op, *exprs = ast
for expr in exprs[:-1]:
EVAL(expr, env)
ast = exprs[-1]
continue
func, *args = eval_ast(ast, env)
if not is_mal_function(func):
# core function
return func(*args)
ast = func.ast
env = Env(func.env, func.params, args)