boa2/boa/primitives.py

   1 """Standard Lisp primitives
   2
   3   Lisp type        Python representation
   4   ---------        ---------------------
   5   pair             class cons
   6   '()              None
   7   symbol           class symbol
   8
   9
  10 """
  11
  12 from error import *
  13
  14 __all__ = ["cons", "car", "cdr", "null_p", "pair_p", "pylist",
  15            "cadr", "caar", "cddr", "caddr", "caadr", "cdadr", "cadddr",
  16            "set_car", "set_cdr", "symbol", "list", "map",
  17            "true", "false", "eq_p", "number_p", "symbol_p", "string_p",
  18            "display", "newline", "symbol_to_string",
  19            "+", "-"]
  20
  21 # pair
  22 ######
  23
  24 class cons(object):
  25     __slots__ = ('car', 'cdr')
  26     def __init__(self, car, cdr):
  27         self.car = car
  28         self.cdr = cdr
  29     def __eq__(self, o):
  30         return pair_p(o) and self.car == o.car and self.cdr == o.cdr
  31
  32 def pair_p(p):
  33     return type(p) is cons
  34
  35 def null_p(o):
  36     return o is None
  37
  38 def car(p):
  39     if pair_p(p): return p.car
  40     else: error("CAR: expects a non-empty <pair>; given %s", p)
  41
  42 def cdr(p):
  43     if pair_p(p): return p.cdr
  44     else: error("CDR: expects a non-empty <pair>; given %s", p)
  45
  46 def set_car(p,v):
  47     if pair_p(p): p.car = v
  48     else: error("CAR: expects a non-empty <pair>; given %s", p)
  49
  50 def set_cdr(p,v):
  51     if pair_p(p): p.cdr = v
  52     else: error("CDR: expects a non-empty <pair>; given %s", p)
  53
  54 # TODO: complete the combinations
  55 def cadr(x): return car(cdr(x))
  56 def caar(x): return car(car(x))
  57 def cddr(x): return cdr(cdr(x))
  58 def caddr(x): return car(cdr(cdr(x)))
  59 def caadr(x): return car(car(cdr(x)))
  60 def cadar(x): return car(cdr(car(x)))
  61 def cdadr(x): return cdr(car(cdr(x)))
  62 def caddr(x): return car(cdr(cdr(x)))
  63 def cadddr(x): return car(cdr(cdr(cdr(x))))
  64
  65 def list(*args):
  66     l = None
  67     for a in reversed(args):
  68         l = cons(a, l)
  69     return l
  70
  71 def map(function, ls):
  72     result = []
  73     while not null_p(ls):
  74         result.append(function(car(ls)))
  75         ls = cdr(ls)
  76     return list(*result)
  77
  78 def pylist(ls):
  79     result = []
  80     while not null_p(ls):
  81         result.append(car(ls))
  82         ls = cdr(ls)
  83     return result
  84
  85 # symbol
  86 ########
  87
  88 class symbol(object):
  89     __slot__ = ('string')
  90     def __init__(self, string):
  91         self.string = string
  92     def __hash__(self):
  93         return hash(self.string)
  94     def __eq__(self, o):
  95         return type(o) is symbol and self.string == o.string
  96     def __str__(self):
  97         return "<symbol: %s>" % self.string
  98     __repr__ = __str__
  99
 100 def symbol_p(sym):
 101     return type(sym) is symbol
 102
 103 def symbol_to_string(sym):
 104     if symbol_p(sym): return sym.string
 105     else: error("symbol->string: expets a <symbol>; given %s", sym)
 106
 107 def string_to_symbol(s):
 108     return symbol(s)
 109
 110 # misc
 111 ######
 112
 113 true = True
 114 false = False
 115
 116 def eq_p(x, y):
 117     return x == y
 118
 119 def number_p(n):
 120     return type(n) in (int, float)
 121
 122 def string_p(s):
 123     return type(s) is str
 124
 125 def display(s):
 126     print s
 127     return symbol("ok")
 128
 129 def newline():
 130     print
 131     return symbol("ok")
 132
 133 # math
 134 ######
 135
 136 globals()["+"] = lambda *args: sum(args)
 137 globals()["-"] = lambda a,b: a-b