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