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"""
Preliminary module to handle fortran formats for IO. Does not use this outside
scipy.sparse io for now, until the API is deemed reasonable.
The *Format classes handle conversion between fortran and python format, and
FortranFormatParser can create *Format instances from raw fortran format
strings (e.g. '(3I4)', '(10I3)', etc...)
"""
import re
import warnings
import numpy as np
__all__ = ["BadFortranFormat", "FortranFormatParser", "IntFormat", "ExpFormat"]
TOKENS = {
"LPAR": r"\(",
"RPAR": r"\)",
"INT_ID": r"I",
"EXP_ID": r"E",
"INT": r"\d+",
"DOT": r"\.",
}
class BadFortranFormat(SyntaxError):
pass
def number_digits(n):
return int(np.floor(np.log10(np.abs(n))) + 1)
class IntFormat(object):
@classmethod
def from_number(cls, n, min=None):
"""Given an integer, returns a "reasonable" IntFormat instance to represent
any number between 0 and n if n > 0, -n and n if n < 0
Parameters
----------
n: int
max number one wants to be able to represent
min: int
minimum number of characters to use for the format
Returns
-------
res: IntFormat
IntFormat instance with reasonable (see Note) computed width
Note
----
Reasonable should be understood as the minimal string length necessary
without losing precision. For example, IntFormat.from_number(1) will
return an IntFormat instance of width 2, so that any 0 and 1 may be
represented as 1-character strings without loss of information."""
width = number_digits(n) + 1
if n < 0:
width += 1
repeat = 80 // width
return cls(width, min, repeat=repeat)
def __init__(self, width, min=None, repeat=None):
self.width = width
self.repeat = repeat
self.min = min
def __repr__(self):
r = "IntFormat("
if self.repeat:
r += "%d" % self.repeat
r += "I%d" % self.width
if self.min:
r += ".%d" % self.min
return r + ")"
@property
def fortran_format(self):
r = "("
if self.repeat:
r += "%d" % self.repeat
r += "I%d" % self.width
if self.min:
r += ".%d" % self.min
return r + ")"
@property
def python_format(self):
return "%" + str(self.width) + "d"
class ExpFormat(object):
@classmethod
def from_number(cls, n, min=None):
"""Given a float number, returns a "reasonable" ExpFormat instance to
represent any number between -n and n.
Parameters
----------
n: float
max number one wants to be able to represent
min: int
minimum number of characters to use for the format
Returns
-------
res: ExpFormat
ExpFormat instance with reasonable (see Note) computed width
Note
----
Reasonable should be understood as the minimal string length necessary
to avoid losing precision."""
# len of one number in exp format: sign + 1|0 + "." +
# number of digit for fractional part + 'E' + sign of exponent +
# len of exponent
finfo = np.finfo(n.dtype)
# Number of digits for fractional part
n_prec = finfo.precision + 1
# Number of digits for exponential part
n_exp = number_digits(np.max(np.abs([finfo.maxexp, finfo.minexp])))
width = 1 + 1 + n_prec + 1 + n_exp + 1
if n < 0:
width += 1
repeat = int(np.floor(80 / width))
return cls(width, n_prec, min, repeat=repeat)
def __init__(self, width, significand, min=None, repeat=None):
"""\
Parameters
----------
width: int
number of characters taken by the string (includes space).
"""
self.width = width
self.significand = significand
self.repeat = repeat
self.min = min
def __repr__(self):
r = "ExpFormat("
if self.repeat:
r += "%d" % self.repeat
r += "E%d.%d" % (self.width, self.significand)
if self.min:
r += "E%d" % self.min
return r + ")"
@property
def fortran_format(self):
r = "("
if self.repeat:
r += "%d" % self.repeat
r += "E%d.%d" % (self.width, self.significand)
if self.min:
r += "E%d" % self.min
return r + ")"
@property
def python_format(self):
return "%" + str(self.width-1) + "." + str(self.significand) + "E"
class Token(object):
def __init__(self, type, value, pos):
self.type = type
self.value = value
self.pos = pos
def __str__(self):
return """Token('%s', "%s")""" % (self.type, self.value)
def __repr__(self):
return self.__str__()
class Tokenizer(object):
def __init__(self):
self.tokens = TOKENS.keys()
self.res = [re.compile(TOKENS[i]) for i in self.tokens]
def input(self, s):
self.data = s
self.curpos = 0
self.len = len(s)
def next_token(self):
curpos = self.curpos
tokens = self.tokens
while curpos < self.len:
for i, r in enumerate(self.res):
m = r.match(self.data, curpos)
if m is None:
continue
else:
self.curpos = m.end()
return Token(self.tokens[i], m.group(), self.curpos)
else:
raise SyntaxError("Unknown character at position %d (%s)" \
% (self.curpos, self.data[curpos]))
# Grammar for fortran format:
# format : LPAR format_string RPAR
# format_string : repeated | simple
# repeated : repeat simple
# simple : int_fmt | exp_fmt
# int_fmt : INT_ID width
# exp_fmt : simple_exp_fmt
# simple_exp_fmt : EXP_ID width DOT significand
# extended_exp_fmt : EXP_ID width DOT significand EXP_ID ndigits
# repeat : INT
# width : INT
# significand : INT
# ndigits : INT
# Naive fortran formatter - parser is hand-made
class FortranFormatParser(object):
"""Parser for fortran format strings. The parse method returns a *Format
instance.
Note
----
Only ExpFormat (exponential format for floating values) and IntFormat
(integer format) for now.
"""
def __init__(self):
self.tokenizer = Tokenizer()
def parse(self, s):
self.tokenizer.input(s)
tokens = []
try:
while True:
t = self.tokenizer.next_token()
if t is None:
break
else:
tokens.append(t)
return self._parse_format(tokens)
except SyntaxError, e:
raise BadFortranFormat(str(e))
def _get_min(self, tokens):
next = tokens.pop(0)
if not next.type == "DOT":
raise SyntaxError()
next = tokens.pop(0)
return next.value
def _expect(self, token, tp):
if not token.type == tp:
raise SyntaxError()
def _parse_format(self, tokens):
if not tokens[0].type == "LPAR":
raise SyntaxError("Expected left parenthesis at position "\
"%d (got '%s')" % (0, tokens[0].value))
elif not tokens[-1].type == "RPAR":
raise SyntaxError("Expected right parenthesis at position "\
"%d (got '%s')" % (len(tokens), tokens[-1].value))
tokens = tokens[1:-1]
types = [t.type for t in tokens]
if types[0] == "INT":
repeat = int(tokens.pop(0).value)
else:
repeat = None
next = tokens.pop(0)
if next.type == "INT_ID":
next = self._next(tokens, "INT")
width = int(next.value)
if tokens:
min = int(self._get_min(tokens))
else:
min = None
return IntFormat(width, min, repeat)
elif next.type == "EXP_ID":
next = self._next(tokens, "INT")
width = int(next.value)
next = self._next(tokens, "DOT")
next = self._next(tokens, "INT")
significand = int(next.value)
if tokens:
next = self._next(tokens, "EXP_ID")
next = self._next(tokens, "INT")
min = int(next.value)
else:
min = None
return ExpFormat(width, significand, min, repeat)
else:
raise SyntaxError("Invalid formater type %s" % next.value)
def _next(self, tokens, tp):
if not len(tokens) > 0:
raise SyntaxError()
next = tokens.pop(0)
self._expect(next, tp)
return next
|
