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# ## Actinide Types
from collections import namedtuple
from decimal import Decimal, InvalidOperation
# Circular import. Hard to avoid: Procedure calls `eval`, `eval` calls
# `lambda_`, `lambda_` eventually calls `Procedure`. We indirect the call
# through the module object to avoid problems with import order.
from . import evaluator as e
from .environment import *
from .builtin import make_registry
ACTINIDE_BINDINGS, ACTINIDE_VOIDS, ACTINIDE_FNS, ACTINIDE_BUILTINS, bind, void, fn, builtin = make_registry()
# ### Nil
#
# Nil is a type with a single value, usually taken to denote no value.
nil = bind('nil', None)
@fn
def nil_p(value):
return value is None
@fn
def read_nil(value):
return nil
@fn
def display_nil(value):
return '()'
# ### Booleans
#
# The true and false values.
true = bind('#t', True)
false = bind('#f', False)
@fn
def boolean_p(value):
return value is true or value is false
@fn
def read_boolean(value):
if value == '#t':
return true
if value == '#f':
return false
return None
@fn
def display_boolean(value):
return '#t' if value else '#f'
# ### Integers
#
# These are fixed-precision numbers with no decimal part, obeying common notions
# of machine integer arithmetic. They support large values.
integer = bind('integer', int)
@fn
def integer_p(value):
return isinstance(value, integer)
@fn
def read_integer(value):
try:
return integer(value)
except ValueError:
return nil
@fn
def display_integer(value):
return str(value)
# ### Decimals
#
# These are variable-precision numbers, which may have a decimal part.
decimal = bind('decimal', Decimal)
@fn
def decimal_p(value):
return isinstance(value, decimal)
@fn
def read_decimal(value):
try:
return decimal(value)
except InvalidOperation:
return nil
@fn
def display_decimal(value):
return str(value)
# ### Strings
#
# Sequences of characters.
string = bind('string', str)
@fn
def string_p(value):
return not symbol_p(value) and isinstance(value, string)
@fn
def read_string(value):
value = value[1:-1]
value = value.replace('\\"', '"')
value = value.replace('\\\\', '\\')
return value
@fn
def display_string(value):
value = value.replace('\\', '\\\\')
value = value.replace('"', '\\"')
return f'"{value}"'
# ### Symbols
#
# Short, interned strings used as identifiers. Interning is handled by a
# SymbolTable.
class Symbol(object):
def __init__(self, value):
self.value = value
def __hash__(self):
return hash(self.value)
def __str__(self):
return f"{self.value}"
def __repr__(self):
return f'Symbol({repr(self.value)})'
# bind manually, fix the symbol table
def symbol(string, symbol_table):
return symbol_table[string]
@fn
def symbol_p(value):
return isinstance(value, Symbol)
@fn
def read_symbol(value, symbol_table):
return symbol(value, symbol_table)
@fn
def display_symbol(value):
return str(value)
# ### Conses
#
# Pairs.
Cons = namedtuple('Cons', 'head tail')
@fn
def cons(head, tail):
return Cons(head, tail)
@fn
def cons_p(value):
return isinstance(value, Cons)
@fn
def head(cons):
return cons.head
@fn
def tail(cons):
return cons.tail
@fn
def display_cons(value):
parts = []
while cons_p(value):
parts.append(display(head(value)))
value = tail(value)
if not nil_p(value):
parts.append('.')
parts.append(display(value))
return '(' + ' '.join(parts) + ')'
# ### Lists
@fn
def list(*elems):
if elems:
head, *tail = elems
return cons(head, list(*tail))
else:
return nil
@fn
def list_p(value):
return nil_p(value) or cons_p(value) and list_p(tail(value))
def flatten(list):
r = []
while not nil_p(list):
r.append(head(list))
list = tail(list)
return r
# ### Procedures
class Procedure(object):
def __init__(self, body, formals, environment, symbols):
self.body = body
self.continuation = e.eval(body, symbols, None)
self.formals = formals
self.environment = environment
def __call__(self, *args):
call_env = self.invocation_environment(*args)
return e.run(self.continuation, call_env, ())
def invocation_environment(self, *args):
return Environment(zip(self.formals, args), self.environment)
@fn
def procedure_p(value):
return callable(value)
@fn
def display_procedure(proc):
if isinstance(proc, Procedure):
formals = ' '.join(display(formal) for formal in proc.formals)
body = display(proc.body)
return f'<procedure: (lambda ({formals}) {body})>'
return f'<builtin: {proc.__name__}>'
# ### General-purpose functions
@fn
def display(value):
if cons_p(value):
return display_cons(value)
if symbol_p(value):
return display_symbol(value)
if string_p(value):
return display_string(value)
if nil_p(value):
return display_nil(value)
if boolean_p(value):
return display_boolean(value)
if integer_p(value):
return display_integer(value)
if decimal_p(value):
return display_decimal(value)
if procedure_p(value):
return display_procedure(value)
# Give up and use repr to avoid printing `None`.
return repr(value)
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