mirrors/z3
3
0
Fork 0
mirror of https://github.com/Z3Prover/z3 synced 2025-04-30 12:25:51 +00:00
Code Activity

Adding python interface for computing with algebraic numbers

Browse source 
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
This commit is contained in:
Leonardo de Moura 2012-12-08 10:57:05 -08:00
parent 47edff2076
commit 277244098c
1 changed files with 489 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

489
src/api/python/z3num.py Normal file
View file

@ -0,0 +1,489 @@
############################################
# Copyright (c) 2012 Microsoft Corporation
#
# Z3 Python interface for Z3 numerals
#
# Author: Leonardo de Moura (leonardo)
############################################
from z3 import *
from z3core import *
from z3printer import *
def _to_algebraic(num, ctx=None):
if isinstance(num, Numeral):
return num
else:
return Numeral(num, ctx)
class Numeral:
"""
A Z3 numeral can be used to perform computations over arbitrary
precision integers, rationals and real algebraic numbers.
It also automatically converts python numeric values.
>>> Numeral(2)
2
>>> Numeral("3/2") + 1
5/2
>>> Numeral(Sqrt(2))
1.4142135623?
>>> Numeral(Sqrt(2)) + 2
3.4142135623?
>>> Numeral(Sqrt(2)) + Numeral(Sqrt(3))
3.1462643699?
Z3 numerals can be used to perform computations with
values in a Z3 model.
>>> s = Solver()
>>> x = Real('x')
>>> s.add(x*x == 2)
>>> s.add(x > 0)
>>> s.check()
sat
>>> m = s.model()
>>> m[x]
1.4142135623?
>>> m[x] + 1
1.4142135623? + 1
The previous result is a Z3 expression.
>>> (m[x] + 1).sexpr()
'(+ (root-obj (+ (^ x 2) (- 2)) 2) 1.0)'
>>> Numeral(m[x]) + 1
2.4142135623?
>>> Numeral(m[x]).is_pos()
True
>>> Numeral(m[x])**2
2
"""
def __init__(self, num, ctx=None):
if isinstance(num, Ast):
self.ast = num
self.ctx = z3._get_ctx(ctx)
elif isinstance(num, RatNumRef) or isinstance(num, AlgebraicNumRef):
self.ast = num.ast
self.ctx = num.ctx
elif isinstance(num, ArithRef):
r = simplify(num)
self.ast = r.ast
self.ctx = r.ctx
else:
v = RealVal(num, ctx)
self.ast = v.ast
self.ctx = v.ctx
Z3_inc_ref(self.ctx_ref(), self.as_ast())
assert Z3_algebraic_is_value(self.ctx_ref(), self.ast)
def __del__(self):
Z3_dec_ref(self.ctx_ref(), self.as_ast())
def __str__(self):
if Z3_is_numeral_ast(self.ctx_ref(), self.ast):
return str(RatNumRef(self.ast, self.ctx))
else:
return str(AlgebraicNumRef(self.ast, self.ctx))
def __repr__(self):
return self.__str__()
def sexpr(self):
return Z3_ast_to_string(self.ctx_ref(), self.as_ast())
def as_ast(self):
return self.ast
def ctx_ref(self):
return self.ctx.ref()
def is_integer(self):
""" Return True if the numeral is integer.
>>> Numeral(2).is_integer()
True
>>> (Numeral(Sqrt(2)) * Numeral(Sqrt(2))).is_integer()
True
>>> Numeral(Sqrt(2)).is_integer()
False
>>> Numeral("2/3").is_integer()
False
"""
return self.is_rational() and self.denominator() == 1
def is_rational(self):
""" Return True if the numeral is rational.
>>> Numeral(2).is_rational()
True
>>> Numeral("2/3").is_rational()
True
>>> Numeral(Sqrt(2)).is_rational()
False
"""
return Z3_get_ast_kind(self.ctx_ref(), self.as_ast()) == Z3_NUMERAL_AST
def denominator(self):
""" Return the denominator if `self` is rational.
>>> Numeral("2/3").denominator()
3
"""
assert(self.is_rational())
return Numeral(Z3_get_denominator(self.ctx_ref(), self.as_ast()), self.ctx)
def numerator(self):
""" Return the numerator if `self` is rational.
>>> Numeral("2/3").numerator()
2
"""
assert(self.is_rational())
return Numeral(Z3_get_numerator(self.ctx_ref(), self.as_ast()), self.ctx)
def is_irrational(self):
""" Return True if the numeral is irrational.
>>> Numeral(2).is_irrational()
False
>>> Numeral("2/3").is_irrational()
False
>>> Numeral(Sqrt(2)).is_irrational()
True
"""
return not self.is_rational()
def as_long(self):
""" Return a numeral (that is an integer) as a Python long.
>>> (Numeral(10)**20).as_long()
100000000000000000000L
"""
assert(self.is_integer())
return long(Z3_get_numeral_string(self.ctx_ref(), self.as_ast()))
def approx(self, precision=10):
"""Return a numeral that approximates the numeral `self`.
The result `r` is such that |r - self| <= 1/10^precision
If `self` is rational, then the result is `self`.
>>> x = Numeral(2).root(2)
>>> x.approx(20)
6838717160008073720548335/4835703278458516698824704
>>> x.approx(5)
2965821/2097152
>>> Numeral(2).approx(10)
2
"""
return self.upper(precision)
def upper(self, precision=10):
"""Return a upper bound that approximates the numeral `self`.
The result `r` is such that r - self <= 1/10^precision
If `self` is rational, then the result is `self`.
>>> x = Numeral(2).root(2)
>>> x.upper(20)
6838717160008073720548335/4835703278458516698824704
>>> x.upper(5)
2965821/2097152
>>> Numeral(2).upper(10)
2
"""
if self.is_rational():
return self
else:
return Numeral(Z3_get_algebraic_number_upper(self.ctx_ref(), self.as_ast(), precision), self.ctx)
def lower(self, precision=10):
"""Return a lower bound that approximates the numeral `self`.
The result `r` is such that self - r <= 1/10^precision
If `self` is rational, then the result is `self`.
>>> x = Numeral(2).root(2)
>>> x.lower(20)
1709679290002018430137083/1208925819614629174706176
>>> Numeral("2/3").lower(10)
2/3
"""
if self.is_rational():
return self
else:
return Numeral(Z3_get_algebraic_number_lower(self.ctx_ref(), self.as_ast(), precision), self.ctx)
def sign(self):
""" Return the sign of the numeral.
>>> Numeral(2).sign()
1
>>> Numeral(-3).sign()
-1
>>> Numeral(0).sign()
0
"""
return Z3_algebraic_sign(self.ctx_ref(), self.ast)
def is_pos(self):
""" Return True if the numeral is positive.
>>> Numeral(2).is_pos()
True
>>> Numeral(-3).is_pos()
False
>>> Numeral(0).is_pos()
False
"""
return Z3_algebraic_is_pos(self.ctx_ref(), self.ast)
def is_neg(self):
""" Return True if the numeral is negative.
>>> Numeral(2).is_neg()
False
>>> Numeral(-3).is_neg()
True
>>> Numeral(0).is_neg()
False
"""
return Z3_algebraic_is_neg(self.ctx_ref(), self.ast)
def is_zero(self):
""" Return True if the numeral is zero.
>>> Numeral(2).is_zero()
False
>>> Numeral(-3).is_zero()
False
>>> Numeral(0).is_zero()
True
>>> sqrt2 = Numeral(2).root(2)
>>> sqrt2.is_zero()
False
>>> (sqrt2 - sqrt2).is_zero()
True
"""
return Z3_algebraic_is_zero(self.ctx_ref(), self.ast)
def __add__(self, other):
""" Return the numeral `self + other`.
>>> Numeral(2) + 3
5
>>> Numeral(2) + Numeral(4)
6
>>> Numeral("2/3") + 1
5/3
"""
return Numeral(Z3_algebraic_add(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast), self.ctx)
def __radd__(self, other):
""" Return the numeral `other + self`.
>>> 3 + Numeral(2)
5
"""
return Numeral(Z3_algebraic_add(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast), self.ctx)
def __sub__(self, other):
""" Return the numeral `self - other`.
>>> Numeral(2) - 3
-1
"""
return Numeral(Z3_algebraic_sub(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast), self.ctx)
def __rsub__(self, other):
""" Return the numeral `other - self`.
>>> 3 - Numeral(2)
1
"""
return Numeral(Z3_algebraic_sub(self.ctx_ref(), _to_algebraic(other, self.ctx).ast, self.ast), self.ctx)
def __mul__(self, other):
""" Return the numeral `self * other`.
>>> Numeral(2) * 3
6
"""
return Numeral(Z3_algebraic_mul(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast), self.ctx)
def __rmul__(self, other):
""" Return the numeral `other * mul`.
>>> 3 * Numeral(2)
6
"""
return Numeral(Z3_algebraic_mul(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast), self.ctx)
def __div__(self, other):
""" Return the numeral `self / other`.
>>> Numeral(2) / 3
2/3
>>> Numeral(2).root(2) / 3
0.4714045207?
>>> Numeral(Sqrt(2)) / Numeral(Sqrt(3))
0.8164965809?
"""
return Numeral(Z3_algebraic_div(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast), self.ctx)
def __rdiv__(self, other):
""" Return the numeral `other / self`.
>>> 3 / Numeral(2)
3/2
>>> 3 / Numeral(2).root(2)
2.1213203435?
"""
return Numeral(Z3_algebraic_div(self.ctx_ref(), _to_algebraic(other, self.ctx).ast, self.ast), self.ctx)
def root(self, k):
""" Return the numeral `self^(1/k)`.
>>> sqrt2 = Numeral(2).root(2)
>>> sqrt2
1.4142135623?
>>> sqrt2 * sqrt2
2
>>> sqrt2 * 2 + 1
3.8284271247?
>>> (sqrt2 * 2 + 1).sexpr()
'(root-obj (+ (^ x 2) (* (- 2) x) (- 7)) 2)'
"""
return Numeral(Z3_algebraic_root(self.ctx_ref(), self.ast, k), self.ctx)
def power(self, k):
""" Return the numeral `self^k`.
>>> sqrt3 = Numeral(3).root(2)
>>> sqrt3
1.7320508075?
>>> sqrt3.power(2)
3
"""
return Numeral(Z3_algebraic_power(self.ctx_ref(), self.ast, k), self.ctx)
def __pow__(self, k):
""" Return the numeral `self^k`.
>>> sqrt3 = Numeral(3).root(2)
>>> sqrt3
1.7320508075?
>>> sqrt3**2
3
"""
return self.power(k)
def __lt__(self, other):
""" Return True if `self < other`.
>>> Numeral(Sqrt(2)) < 2
True
>>> Numeral(Sqrt(3)) < Numeral(Sqrt(2))
False
>>> Numeral(Sqrt(2)) < Numeral(Sqrt(2))
False
"""
return Z3_algebraic_lt(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast)
def __rlt__(self, other):
""" Return True if `other < self`.
>>> 2 < Numeral(Sqrt(2))
False
"""
return self > other
def __gt__(self, other):
""" Return True if `self > other`.
>>> Numeral(Sqrt(2)) > 2
False
>>> Numeral(Sqrt(3)) > Numeral(Sqrt(2))
True
>>> Numeral(Sqrt(2)) > Numeral(Sqrt(2))
False
"""
return Z3_algebraic_gt(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast)
def __rgt__(self, other):
""" Return True if `other > self`.
>>> 2 > Numeral(Sqrt(2))
True
"""
return self < other
def __le__(self, other):
""" Return True if `self <= other`.
>>> Numeral(Sqrt(2)) <= 2
True
>>> Numeral(Sqrt(3)) <= Numeral(Sqrt(2))
False
>>> Numeral(Sqrt(2)) <= Numeral(Sqrt(2))
True
"""
return Z3_algebraic_le(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast)
def __rle__(self, other):
""" Return True if `other <= self`.
>>> 2 <= Numeral(Sqrt(2))
False
"""
return self >= other
def __ge__(self, other):
""" Return True if `self >= other`.
>>> Numeral(Sqrt(2)) >= 2
False
>>> Numeral(Sqrt(3)) >= Numeral(Sqrt(2))
True
>>> Numeral(Sqrt(2)) >= Numeral(Sqrt(2))
True
"""
return Z3_algebraic_ge(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast)
def __rge__(self, other):
""" Return True if `other >= self`.
>>> 2 >= Numeral(Sqrt(2))
True
"""
return self <= other
def __eq__(self, other):
""" Return True if `self == other`.
>>> Numeral(Sqrt(2)) == 2
False
>>> Numeral(Sqrt(3)) == Numeral(Sqrt(2))
False
>>> Numeral(Sqrt(2)) == Numeral(Sqrt(2))
True
"""
return Z3_algebraic_eq(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast)
def __ne__(self, other):
""" Return True if `self != other`.
>>> Numeral(Sqrt(2)) != 2
True
>>> Numeral(Sqrt(3)) != Numeral(Sqrt(2))
True
>>> Numeral(Sqrt(2)) != Numeral(Sqrt(2))
False
"""
return Z3_algebraic_neq(self.ctx_ref(), self.ast, _to_algebraic(other, self.ctx).ast)
if __name__ == "__main__":
import doctest
doctest.testmod()