%a format

[Jeff Epler]

# This file is in the public domain
import random,math, struct

def hexf(d):
    q, = struct.unpack("Q", struct.pack("d", d))
    man = q & 0xfffffffffffff
    sgn = ["", "-"][q >> 63]
    bexp = (q >> 52) & 0x7ff
    exp = bexp - 0x3ff
    esgn = ["+", "-"][exp < 0]
    if bexp == 0x7ff:
        # SNan, QNan, or infinity
        return str(d)
    elif bexp == 0x0:
        # Denormal or zero
        if not man:
            return "%s0X0P0" % sgn
        imp = 1l<<52
        exp += 1
        while not man & imp:
            man <<= 1
            exp -= 1
    else:
        man = man + (1l<<52)
    hman = hex(man)[2:-1]
    hman = hman.rstrip("0")
    if len(hman) == 1:
        return "%s0X%sP%d" % (sgn, hman, exp)
    else:
        return "%s0X%s.%sP%d" % (sgn, hman[0], hman[1:], exp)

def test():
    inf = float("inf"); ninf = -inf
    nan = float("nan"); nnan = -nan
    pairs = [
        (0, "0X0P0"),
        (-1.*0, "-0X0P0"),
        (1, "0X1P0"),
        (.5, "0X1P-1"),
        (2, "0X1P1"),
        (1.5, "0X1.8P0"),
        (2.**10, "0X1P10"),
        (2.**-10, "0X1P-10"),
        (2.**-320, "0X1P-320"),
        (2.**-1024, "0X1P-1024"),
        (2.**-1060, "0X1P-1060"),
        (2.**1020, "0X1P1020"),
        (-1, "-0X1P0"),
        (-.5, "-0X1P-1"),
        (1-2.**-53, "0X1.FFFFFFFFFFFFFP-1"),
        (-2, "-0X1P1"),
        (-1.5, "-0X1.8P0"),
        (-2.**10, "-0X1P10"),
        (-2.**-10, "-0X1P-10"),
        (-2.**-320, "-0X1P-320"),
        (-2.**-1024, "-0X1P-1024"),
        (-2.**-1060, "-0X1P-1060"),
        (-2.**1020, "-0X1P1020"),
        (-(1-2.**-53), "-0X1.FFFFFFFFFFFFFP-1"),
        (inf, str(inf)),
        (ninf, str(ninf)),
        (nan, str(nan)),
        (nnan, str(nnan)),
    ]
    success = 0
    for f, s in pairs:
        t = hexf(f)
        print repr(f), t
        if t != s:
            print "FAIL", f, s, t
        else:
            success += 1
    if success == len(pairs):
        print "SUCCESS", success

if __name__ == '__main__': test()
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