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Merge pull request #106 from fluentpython/main

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lispy.py now runs in Python 3; dropped Python 2 support
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Peter Norvig 2021-06-29 09:12:49 -07:00 committed by GitHub
commit 286b31bcca
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1 changed files with 30 additions and 32 deletions
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py/lispy.py
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@ -4,9 +4,7 @@
################ Symbol, Procedure, classes
from __future__ import division
from __future__ import print_function
import re, sys, StringIO
import re, sys, io
class Symbol(str): pass
@ -15,17 +13,17 @@ def Sym(s, symbol_table={}):
if s not in symbol_table: symbol_table[s] = Symbol(s)
return symbol_table[s]
_quote, _if, _set, _define, _lambda, _begin, _definemacro, = map(Sym,
_quote, _if, _set, _define, _lambda, _begin, _definemacro, = map(Sym,
"quote if set! define lambda begin define-macro".split())
_quasiquote, _unquote, _unquotesplicing = map(Sym,
"quasiquote unquote unquote-splicing".split())
class Procedure(object):
class Procedure:
"A user-defined Scheme procedure."
def __init__(self, parms, exp, env):
self.parms, self.exp, self.env = parms, exp, env
def __call__(self, *args):
def __call__(self, *args):
return eval(self.exp, Env(self.parms, args, self.env))
################ parse, read, and user interaction
@ -33,12 +31,12 @@ class Procedure(object):
def parse(inport):
"Parse a program: read and expand/error-check it."
# Backwards compatibility: given a str, convert it to an InPort
if isinstance(inport, str): inport = InPort(StringIO.StringIO(inport))
if isinstance(inport, str): inport = InPort(io.StringIO(inport))
return expand(read(inport), toplevel=True)
eof_object = Symbol('#<eof-object>') # Note: uninterned; can't be read
class InPort(object):
class InPort:
"An input port. Retains a line of chars."
tokenizer = r"""\s*(,@|[('`,)]|"(?:[\\].|[^\\"])*"|;.*|[^\s('"`,;)]*)(.*)"""
def __init__(self, file):
@ -63,7 +61,7 @@ def readchar(inport):
def read(inport):
"Read a Scheme expression from an input port."
def read_ahead(token):
if '(' == token:
if '(' == token:
L = []
while True:
token = inport.next_token()
@ -83,7 +81,7 @@ def atom(token):
'Numbers become numbers; #t and #f are booleans; "..." string; otherwise Symbol.'
if token == '#t': return True
elif token == '#f': return False
elif token[0] == '"': return token[1:-1].decode('string_escape')
elif token[0] == '"': return token[1:-1]
try: return int(token)
except ValueError:
try: return float(token)
@ -97,7 +95,7 @@ def to_string(x):
if x is True: return "#t"
elif x is False: return "#f"
elif isa(x, Symbol): return x
elif isa(x, str): return '"%s"' % x.encode('string_escape').replace('"',r'\"')
elif isa(x, str): return repr(x)
elif isa(x, list): return '('+' '.join(map(to_string, x))+')'
elif isa(x, complex): return str(x).replace('j', 'i')
else: return str(x)
@ -126,11 +124,11 @@ class Env(dict):
def __init__(self, parms=(), args=(), outer=None):
# Bind parm list to corresponding args, or single parm to list of args
self.outer = outer
if isa(parms, Symbol):
if isa(parms, Symbol):
self.update({parms:list(args)})
else:
else:
if len(args) != len(parms):
raise TypeError('expected %s, given %s, '
raise TypeError('expected %s, given %s, '
% (to_string(parms), to_string(args)))
self.update(zip(parms,args))
def find(self, var):
@ -158,16 +156,16 @@ def add_globals(self):
self.update(vars(math))
self.update(vars(cmath))
self.update({
'+':op.add, '-':op.sub, '*':op.mul, '/':op.div, 'not':op.not_,
'>':op.gt, '<':op.lt, '>=':op.ge, '<=':op.le, '=':op.eq,
'+':op.add, '-':op.sub, '*':op.mul, '/':op.truediv, 'not':op.not_,
'>':op.gt, '<':op.lt, '>=':op.ge, '<=':op.le, '=':op.eq,
'equal?':op.eq, 'eq?':op.is_, 'length':len, 'cons':cons,
'car':lambda x:x[0], 'cdr':lambda x:x[1:], 'append':op.add,
'car':lambda x:x[0], 'cdr':lambda x:x[1:], 'append':op.add,
'list':lambda *x:list(x), 'list?': lambda x:isa(x,list),
'null?':lambda x:x==[], 'symbol?':lambda x: isa(x, Symbol),
'boolean?':lambda x: isa(x, bool), 'pair?':is_pair,
'port?': lambda x:isa(x,file), 'apply':lambda proc,l: proc(*l),
'boolean?':lambda x: isa(x, bool), 'pair?':is_pair,
'port?': lambda x:isa(x,file), 'apply':lambda proc,l: proc(*l),
'eval':lambda x: eval(expand(x)), 'load':lambda fn: load(fn), 'call/cc':callcc,
'open-input-file':open,'close-input-port':lambda p: p.file.close(),
'open-input-file':open,'close-input-port':lambda p: p.file.close(),
'open-output-file':lambda f:open(f,'w'), 'close-output-port':lambda p: p.close(),
'eof-object?':lambda x:x is eof_object, 'read-char':readchar,
'read':read, 'write':lambda x,port=sys.stdout:port.write(to_string(x)),
@ -186,7 +184,7 @@ def eval(x, env=global_env):
if isa(x, Symbol): # variable reference
return env.find(x)[x]
elif not isa(x, list): # constant literal
return x
return x
elif x[0] is _quote: # (quote exp)
(_, exp) = x
return exp
@ -227,17 +225,17 @@ def expand(x, toplevel=False):
elif x[0] is _quote: # (quote exp)
require(x, len(x)==2)
return x
elif x[0] is _if:
elif x[0] is _if:
if len(x)==3: x = x + [None] # (if t c) => (if t c None)
require(x, len(x)==4)
return list(map(expand, x))
elif x[0] is _set:
require(x, len(x)==3);
elif x[0] is _set:
require(x, len(x)==3);
var = x[1] # (set! non-var exp) => Error
require(x, isa(var, Symbol), "can set! only a symbol")
return [_set, var, expand(x[2])]
elif x[0] is _define or x[0] is _definemacro:
require(x, len(x)>=3)
elif x[0] is _define or x[0] is _definemacro:
require(x, len(x)>=3)
_def, v, body = x[0], x[1], x[2:]
if isa(v, list) and v: # (define (f args) body)
f, args = v[0], v[1:] # => (define f (lambda (args) body))
@ -246,9 +244,9 @@ def expand(x, toplevel=False):
require(x, len(x)==3) # (define non-var/list exp) => Error
require(x, isa(v, Symbol), "can define only a symbol")
exp = expand(x[2])
if _def is _definemacro:
if _def is _definemacro:
require(x, toplevel, "define-macro only allowed at top level")
proc = eval(exp)
proc = eval(exp)
require(x, callable(proc), "macro must be a procedure")
macro_table[v] = proc # (define-macro v proc)
return None # => None; add v:proc to macro_table
@ -256,18 +254,18 @@ def expand(x, toplevel=False):
elif x[0] is _begin:
if len(x)==1: return None # (begin) => None
else: return [expand(xi, toplevel) for xi in x]
elif x[0] is _lambda: # (lambda (x) e1 e2)
elif x[0] is _lambda: # (lambda (x) e1 e2)
require(x, len(x)>=3) # => (lambda (x) (begin e1 e2))
vars, body = x[1], x[2:]
require(x, (isa(vars, list) and all(isa(v, Symbol) for v in vars))
or isa(vars, Symbol), "illegal lambda argument list")
exp = body[0] if len(body) == 1 else [_begin] + body
return [_lambda, vars, expand(exp)]
return [_lambda, vars, expand(exp)]
elif x[0] is _quasiquote: # `x => expand_quasiquote(x)
require(x, len(x)==2)
return expand_quasiquote(x[1])
elif isa(x[0], Symbol) and x[0] in macro_table:
return expand(macro_table[x[0]](*x[1:]), toplevel) # (m arg...)
return expand(macro_table[x[0]](*x[1:]), toplevel) # (m arg...)
else: # => macroexpand if m isa macro
return list(map(expand, x)) # (f arg...) => expand each
@ -305,7 +303,7 @@ macro_table = {_let:let} ## More macros can go here
eval(parse("""(begin
(define-macro and (lambda args
(define-macro and (lambda args
(if (null? args) #t
(if (= (length args) 1) (car args)
`(if ,(car args) (and ,@(cdr args)) #f)))))