Source Code for Module sympycore.arithmetic.evalf

 1  """Provides low-level evalf function.
 
 2  """ 
 3  
 
 4  __all__ = ['evalf'] 
 5  
 
 6  from .numbers import Float, Complex 
 7  
 
 8  import math 
 9  import cmath 
10  import re 
11  import mpmath 
12  
 
13  int_pattern = re.compile('\d+([.]\d+)?') 
14  
 
15 -def quote_numbers(s, format): 
16      return int_pattern.sub(lambda m: (format % m.group()), s) 
17  
 
18 -def replace_names(s, names): 
19      for name, new in names.items(): 
20          s = s.replace(name, new) 
21      return s 
22  
 
23 -def f_header(symbols): 
24      if isinstance(symbols, (tuple, list)): 
25          return "lambda %s: " % ",".join(map(str, symbols)) 
26      if not symbols: 
27          return "lambda: " 
28      return "lambda %s: " % symbols 
29  
 
30 -def convert_mpmath(expr): 
31      s = str(expr) 
32      s = quote_numbers(s, "mpf(%s)") 
33      s = replace_names(s, { 'I':'j', 'E':'e', 'oo':'inf','undefined':'nan'}) 
34      return s 
35  
 
36 -def compile_mpmath(symbols, expr): 
37      s = convert_mpmath(expr) 
38      f = eval(f_header(symbols) + s, vars(mpmath)) 
39      return f 
40  
 
41 -def mpmath_to_numbers(x, digits): 
42      prec = int(digits*3.33) + 12 
43      if isinstance(x, mpmath.mpc): 
44          return Complex(Float(x.real.val, prec), Float(x.imag.val, prec)) 
45      a = object.__new__(Float) 
46      a.val = x.val 
47      a.prec = prec 
48      return a 
49  
 
50 -def evalf(expr, digits=15): 
51      s = convert_mpmath(expr) 
52      mpmath.mpf.dps = digits + 4 
53      return mpmath_to_numbers(eval(s, vars(mpmath)), digits) 
54