circuitpython/tests/float/float2int.py

# check cases converting float to int, relying only on single precision float

try:
    import ustruct as struct
except:
    import struct

# work out configuration values
is_64bit = struct.calcsize("P") == 8
# 0 = none, 1 = long long, 2 = mpz
try:
    dummy = 0x7fffffffffffffff
    try:
        if (0xffffffffffffffff + 1) > 0:
            ll_type = 2
        else:
            ll_type = 1
    except:
        # in case the sum in the if statement above changes to raising an exception on overflow
        ll_type = 1
except:
    ll_type = 0

# basic conversion
print(int(14187745.))
print("%d" % 14187745.)
if ll_type == 2:
    print(int(2.**100))
    print("%d" % 2.**100)

testpass = True
p2_rng = ((30,63,127),(62,63,127))[is_64bit][ll_type]
for i in range(0,p2_rng):
    bitcnt = len(bin(int(2.**i))) - 3;
    if i != bitcnt:
        print('fail: 2**%u was %u bits long' % (i, bitcnt));
        testpass = False
print("power of  2 test: %s" % (testpass and 'passed' or 'failed'))

# TODO why does 10**12 fail this test for single precision float?
testpass = True
p10_rng = 9 if (ll_type == 0 and ~is_64bit) else 11
for i in range(0,p10_rng):
    digcnt = len(str(int(10.**i))) - 1;
    if i != digcnt:
        print('fail: 10**%u was %u digits long' % (i, digcnt));
        testpass = False
print("power of 10 test: %s" % (testpass and 'passed' or 'failed'))

def fp2int_test(num, name, should_fail):
    try:
        x = int(num)
        passed = ~should_fail
    except:
        passed = should_fail
    print('%s: %s' % (name, passed and 'passed' or 'failed'))

if ll_type != 2:
    if ll_type == 0:
        if is_64bit:
            neg_bad_fp = -1.00000005*2.**62.
            pos_bad_fp = 2.**62.
            neg_good_fp = -2.**62.
            pos_good_fp = 0.99999993*2.**62.
        else:
            neg_bad_fp = -1.00000005*2.**30.
            pos_bad_fp = 2.**30.
            neg_good_fp = -2.**30.
            pos_good_fp = 0.9999999499*2.**30.
    else:
        neg_bad_fp = -0.51*2.**64.
        pos_bad_fp = 2.**63.
        neg_good_fp = -2.**63.
        pos_good_fp = 1.9999998*2.**62.

    fp2int_test(neg_bad_fp, 'neg bad', True)
    fp2int_test(pos_bad_fp, 'pos bad', True)
    fp2int_test(neg_good_fp, 'neg good', False)
    fp2int_test(pos_good_fp, 'pos good', False)
else:
    fp2int_test(-1.999999879*2.**127., 'large neg', False)
    fp2int_test(1.999999879*2.**127., 'large pos', False)

fp2int_test(float('inf'), 'inf test', True)
fp2int_test(float('nan'), 'NaN test', True)

# test numbers < 1 (this used to fail; see issue #1044)
fp2int_test(0.0001, 'small num', False)
struct.pack('I', int(1/2))