For loop 为什么我的for循环只从我的表中读取3个值，然后产生错误；尝试索引字段''；（零值）“；。。。价值确实存在

我有一个以数字作为键的表，还有一个表（包含两个数字）作为它们的值。我的目标是创建一个引用多个键的循环，但在for循环的第四次迭代中，我一直得到一个“nil”错误。。。即使键/值确实存在

以下是我正在使用的表格：

local TotalVolume = {[1.508] = {7788000, 3185000},
[1.548] = {8591000, 3115000},
[1.588] = {7660000, 2491000},
[1.5395] = {5696000, 1137000},
[1.5795] = {7633000, 2419000},
[1.4755] = {5278000, 4159000},
[1.5155] = {8502000, 1055000},
[1.5555] = {7438000, 3932000},
[1.4515] = {6426000, 4126000},
[1.5955] = {5101000, 4167000},
[1.4915] = {9132000, 1344000},
[1.5315] = {5053000, 3143000},
[1.5715] = {4940000, 3716000},
[1.4675] = {9107000, 3516000},
[1.5075] = {6984000, 2579000},
[1.5475] = {9424000, 3743000},
[1.5875] = {5519000, 4125000},
[1.4835] = {6844000, 1276000},
[1.5235] = {6150000, 4299000},
[1.5635] = {8303000, 3790000},
[1.4595] = {7359000, 1987000},
[1.4995] = {8329000, 1945000},
[1.451] = {7718000, 2628000},
[1.491] = {8117000, 1612000},
[1.531] = {4532000, 3449000},
[1.571] = {9465000, 2490000},
[1.467] = {7734000, 3388000},
[1.507] = {7955000, 3075000},
[1.547] = {6063000, 3737000},
[1.587] = {6654000, 4455000},
[1.483] = {7344000, 3287000},
[1.523] = {9304000, 3510000},
[1.563] = {8961000, 3284000},
[1.459] = {8809000, 3790000},
[1.499] = {6902000, 1627000},
[1.539] = {8394000, 3122000},
[1.579] = {5329000, 3191000},
[1.475] = {5311000, 4319000},
[1.515] = {9514000, 3113000},
[1.555] = {9704000, 3914000},
[1.595] = {6523000, 2764000},
[1.5465] = {8945000, 1385000},
[1.5865] = {9722000, 4054000},
[1.4825] = {9091000, 1026000},
[1.5225] = {9047000, 4353000},
[1.5625] = {9203000, 1133000},
[1.4585] = {4813000, 3088000},
[1.4985] = {7489000, 1166000},
[1.5385] = {4580000, 1355000},
[1.5785] = {9568000, 3291000},
[1.4745] = {8349000, 2717000},
[1.5145] = {7668000, 4024000},
[1.5545] = {6692000, 2458000},
[1.4505] = {5563000, 3812000},
[1.5945] = {8243000, 4180000},
[1.4905] = {9137000, 3156000},
[1.5305] = {7835000, 2323000},
[1.5705] = {9463000, 1283000},
[1.4665] = {6017000, 1882000},
[1.5065] = {6759000, 1627000},
[1.458] = {6979000, 2167000},
[1.498] = {8637000, 3370000},
[1.538] = {8469000, 3975000},
[1.578] = {9501000, 2540000},
[1.474] = {7205000, 1128000},
[1.514] = {8925000, 1436000},
[1.554] = {6350000, 4193000},
[1.45] = {4506000, 2929000},
[1.594] = {5601000, 1881000},
[1.49] = {7422000, 1598000},
[1.53] = {8285000, 2816000},
[1.57] = {5823000, 2777000},
[1.466] = {4548000, 4208000},
[1.506] = {5750000, 3669000},
[1.546] = {6212000, 1298000},
[1.586] = {7757000, 1618000},
[1.482] = {5176000, 2224000},
[1.522] = {8559000, 2030000},
[1.562] = {4952000, 3276000},
[1.5135] = {7912000, 3388000},
[1.5535] = {4759000, 1111000},
[1.5935] = {8567000, 1401000},
[1.4895] = {7649000, 1081000},
[1.5295] = {7301000, 2276000},
[1.5695] = {5702000, 1461000},
[1.4655] = {8225000, 1102000},
[1.5055] = {9421000, 1944000},
[1.5455] = {7514000, 1712000},
[1.5855] = {6681000, 3909000},
[1.4815] = {8471000, 2611000},
[1.5215] = {5339000, 2063000},
[1.5615] = {4523000, 2404000},
[1.4575] = {5414000, 3287000},
[1.4975] = {5125000, 2536000},
[1.5375] = {9254000, 3049000},
[1.5775] = {8051000, 3264000},
[1.4735] = {5429000, 3266000},
[1.465] = {6567000, 1233000},
[1.505] = {9624000, 1074000},
[1.545] = {7654000, 1988000},
[1.585] = {6927000, 3364000},
[1.481] = {8253000, 3621000},
[1.521] = {7061000, 2704000},
[1.561] = {5723000, 2279000},
[1.457] = {7810000, 3086000},
[1.497] = {7543000, 951000},
[1.537] = {5224000, 3950000},
[1.577] = {5576000, 3707000},
[1.473] = {8634000, 2144000},
[1.513] = {8574000, 3103000},
[1.553] = {9624000, 1188000},
[1.593] = {8600000, 3551000},
[1.489] = {4651000, 4481000},
[1.529] = {7232000, 3756000},
[1.4805] = {6037000, 2948000},
[1.569] = {6521000, 3401000},
[1.5205] = {6749000, 1975000},
[1.5605] = {7672000, 1412000},
[1.4565] = {7424000, 2956000},
[1.4965] = {5658000, 1316000},
[1.5365] = {4807000, 3201000},
[1.5765] = {9370000, 4281000},
[1.4725] = {7344000, 4464000},
[1.5125] = {7220000, 1189000},
[1.5525] = {5306000, 1350000},
[1.5925] = {6444000, 3542000},
[1.4885] = {7255000, 4105000},
[1.5285] = {7209000, 2265000},
[1.5685] = {6107000, 4221000},
[1.4645] = {9121000, 985000},
[1.5045] = {5019000, 2476000},
[1.5445] = {4863000, 2440000},
[1.5845] = {7824000, 3411000},
[1.576] = {5344000, 3133000},
[1.472] = {6838000, 3791000},
[1.512] = {7715000, 2165000},
[1.552] = {9404000, 1738000},
[1.592] = {6634000, 2954000},
[1.488] = {9117000, 2331000},
[1.528] = {8146000, 1312000},
[1.568] = {9900000, 3132000},
[1.464] = {5964000, 1970000},
[1.504] = {5036000, 3151000},
[1.544] = {5251000, 3979000},
[1.584] = {8044000, 2536000},
[1.48] = {8526000, 2360000},
[1.52] = {7498000, 2514000},
[1.56] = {7809000, 3730000},
[1.456] = {4549000, 2260000},
[1.6] = {8487000, 1615000},
[1.496] = {8935000, 3970000},
[1.536] = {4653000, 2087000},
[1.4875] = {5578000, 3641000},
[1.5275] = {9560000, 2884000},
[1.5675] = {6012000, 1422000},
[1.4635] = {7863000, 2313000},
[1.5035] = {7016000, 4493000},
[1.5435] = {6713000, 1813000},
[1.5835] = {5587000, 1461000},
[1.4795] = {5355000, 2714000},
[1.5195] = {8026000, 3852000},
[1.5595] = {4539000, 4288000},
[1.4555] = {5155000, 916000},
[1.5995] = {4873000, 3333000},
[1.4955] = {4508000, 1119000},
[1.5355] = {9735000, 3103000},
[1.5755] = {5541000, 1791000},
[1.4715] = {5333000, 1710000},
[1.5115] = {7826000, 3415000},
[1.5515] = {5020000, 1831000},
[1.5915] = {9472000, 2011000},
[1.543] = {5296000, 3169000},
[1.583] = {7749000, 1155000},
[1.479] = {8995000, 2611000},
[1.519] = {4936000, 1175000},
[1.559] = {6895000, 4105000},
[1.455] = {9937000, 2504000},
[1.599] = {5284000, 2321000},
[1.495] = {5890000, 1420000},
[1.535] = {5224000, 3576000},
[1.575] = {4712000, 1807000},
[1.471] = {7648000, 2201000},
[1.511] = {5836000, 1580000},
[1.551] = {7386000, 2436000},
[1.591] = {6665000, 2331000},
[1.487] = {8566000, 2942000},
[1.527] = {5749000, 1945000},
[1.567] = {9714000, 1111000},
[1.463] = {9983000, 4499000},
[1.503] = {5481000, 4483000},
[1.4545] = {5310000, 1497000},
[1.4945] = {7801000, 3590000},
[1.5345] = {5471000, 2247000},
[1.5745] = {6211000, 4474000},
[1.4705] = {8543000, 3092000},
[1.5105] = {7553000, 4159000},
[1.5505] = {4795000, 1193000},
[1.5905] = {8507000, 4126000},
[1.4865] = {9907000, 1972000},
[1.5265] = {5076000, 2718000},
[1.5665] = {4970000, 2887000},
[1.4625] = {8788000, 3937000},
[1.5025] = {5544000, 2109000},
[1.5425] = {8890000, 4143000},
[1.5825] = {4886000, 2302000},
[1.4785] = {5552000, 1540000},
[1.5185] = {5352000, 2077000},
[1.5585] = {8262000, 4303000},
[1.51] = {5513000, 3557000},
[1.5985] = {6190000, 3410000},
[1.55] = {7483000, 4446000},
[1.59] = {9425000, 3457000},
[1.486] = {7009000, 1879000},
[1.526] = {8096000, 2059000},
[1.566] = {8045000, 3444000},
[1.462] = {9243000, 1654000},
[1.502] = {8327000, 4230000},
[1.542] = {7396000, 3100000},
[1.582] = {8874000, 1607000},
[1.478] = {9020000, 2995000},
[1.518] = {9182000, 3580000},
[1.558] = {7721000, 1818000},
[1.454] = {5002000, 2212000},
[1.598] = {4652000, 2178000},
[1.494] = {9091000, 3449000},
[1.534] = {9757000, 3171000},
[1.574] = {5127000, 2357000},
[1.47] = {7795000, 2287000},
[1.4615] = {7041000, 1747000},
[1.5015] = {7273000, 4367000},
[1.5415] = {8913000, 3805000},
[1.5815] = {6426000, 1031000},
[1.4775] = {5342000, 4058000},
[1.5175] = {5097000, 4029000},
[1.5575] = {6693000, 1768000},
[1.4535] = {6172000, 953000},
[1.5975] = {4937000, 1172000},
[1.4935] = {5271000, 3539000},
[1.5335] = {7541000, 2185000},
[1.5735] = {4520000, 3603000},
[1.4695] = {8595000, 1289000},
[1.5095] = {7612000, 2250000},
[1.5495] = {5762000, 1798000},
[1.5895] = {5931000, 2367000},
[1.4855] = {9159000, 2041000},
[1.5255] = {4897000, 4053000},
[1.477] = {9817000, 3360000},
[1.5655] = {4670000, 4028000},
[1.517] = {6182000, 1526000},
[1.557] = {7391000, 4338000},
[1.453] = {8408000, 2749000},
[1.597] = {8282000, 1225000},
[1.493] = {6073000, 2111000},
[1.533] = {6590000, 3728000},
[1.573] = {5658000, 2544000},
[1.469] = {7019000, 4317000},
[1.509] = {7936000, 3495000},
[1.549] = {5756000, 4009000},
[1.589] = {4772000, 1928000},
[1.485] = {7094000, 2250000},
[1.525] = {7853000, 4342000},
[1.565] = {8504000, 3700000},
[1.461] = {7466000, 1412000},
[1.501] = {7958000, 1476000},
[1.541] = {6521000, 3280000},
[1.581] = {5904000, 2329000},
[1.5725] = {8768000, 4034000},
[1.4685] = {8591000, 2586000},
[1.5085] = {9202000, 3884000},
[1.5485] = {6486000, 3984000},
[1.5885] = {7950000, 3451000},
[1.4845] = {7523000, 2145000},
[1.5245] = {8818000, 2789000},
[1.5645] = {5285000, 3382000},
[1.4605] = {9758000, 4233000},
[1.5005] = {7678000, 2817000},
[1.5405] = {6375000, 2050000},
[1.5805] = {7682000, 2831000},
[1.4765] = {6846000, 1153000},
[1.5165] = {6232000, 2949000},
[1.5565] = {5925000, 915000},
[1.4525] = {5457000, 3993000},
[1.5965] = {8102000, 2479000},
[1.4925] = {6227000, 4288000},
[1.5325] = {8611000, 2689000},
[1.484] = {9722000, 4217000},
[1.524] = {5199000, 1136000},
[1.564] = {7416000, 3368000},
[1.46] = {9318000, 3516000},
[1.5] = {6902000, 1736000},
[1.54] = {5429000, 3147000},
[1.58] = {9687000, 2846000},
[1.476] = {8311000, 1991000},
[1.516] = {8173000, 4416000},
[1.556] = {8315000, 2332000},
[1.452] = {9026000, 3588000},
[1.596] = {5617000, 2765000},
[1.492] = {5104000, 3575000},
[1.532] = {9248000, 2669000},
[1.572] = {5445000, 4408000},
[1.468] = {7167000, 1639000}
}

下面是一个简化的for循环，它会产生我得到的错误：

function testForLoop()

local price = 1.508

    for y = 1,10 do
        print("Checking bucket " ..tostring(price) .. "   --->   Volume = " .. tostring(TotalVolume[price][1]))
        price = price + 0.0005
    end

end

为了显示这些值确实存在于表中，下面是for循环引用的键的简单打印语句（它工作正常）：

---

有人知道在尝试引用此表时，是什么导致for循环失败吗？

问题是，大多数浮点数不能用Lua的数字类型精确表示（即，C中的双精度）。因此，浮点数学并不精确：

> print(1.508 + 0.0005 + 0.0005 + 0.0005 == 1.5095)
false

---

使代码正常工作的一种方法是使用某种舍入。

于浩关于失败原因的解释是正确的。根据可能的解决方案，您可以迭代实际关键点，而不是使用数值：

for price, val in pairs(TotalVolume) do
  print("Checking bucket " ..tostring(price) .. "   --->   Volume = " .. tostring(val[1]))
end

---

啊，谢谢你！我现在记得在我的Lua教科书中读到了这一点，我在想“我什么时候需要知道这些？”。。。非常感谢。

for price, val in pairs(TotalVolume) do
  print("Checking bucket " ..tostring(price) .. "   --->   Volume = " .. tostring(val[1]))
end