/*
    __ _____ _____ _____
 __|  |   __|     |   | |  JSON for Modern C++ (test suite)
|  |  |__   |  |  | | | |  version 3.1.1
|_____|_____|_____|_|___|  https://github.com/nlohmann/json

Licensed under the MIT License <http://opensource.org/licenses/MIT>.
Copyright (c) 2013-2018 Niels Lohmann <http://nlohmann.me>.

Permission is hereby  granted, free of charge, to any  person obtaining a copy
of this software and associated  documentation files (the "Software"), to deal
in the Software  without restriction, including without  limitation the rights
to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

// XXX:
// Only compile these tests if 'float' and 'double' are IEEE-754 single- and
// double-precision numbers, resp.

#include "catch.hpp"

#include <nlohmann/json.hpp>
using nlohmann::detail::dtoa_impl::reinterpret_bits;

static float make_float(uint32_t sign_bit, uint32_t biased_exponent, uint32_t significand)
{
    assert(sign_bit == 0 || sign_bit == 1);
    assert(biased_exponent <= 0xFF);
    assert(significand <= 0x007FFFFF);

    uint32_t bits = 0;

    bits |= sign_bit << 31;
    bits |= biased_exponent << 23;
    bits |= significand;

    return reinterpret_bits<float>(bits);
}

// ldexp -- convert f * 2^e to IEEE single precision
static float make_float(uint64_t f, int e)
{
    constexpr uint64_t kHiddenBit               = 0x00800000;
    constexpr uint64_t kSignificandMask         = 0x007FFFFF;
    constexpr int      kPhysicalSignificandSize = 23;  // Excludes the hidden bit.
    constexpr int      kExponentBias            = 0x7F + kPhysicalSignificandSize;
    constexpr int      kDenormalExponent        = 1 -    kExponentBias;
    constexpr int      kMaxExponent             = 0xFF - kExponentBias;

    while (f > kHiddenBit + kSignificandMask)
    {
        f >>= 1;
        e++;
    }
    if (e >= kMaxExponent)
    {
        return std::numeric_limits<float>::infinity();
    }
    if (e < kDenormalExponent)
    {
        return 0.0;
    }
    while (e > kDenormalExponent && (f & kHiddenBit) == 0)
    {
        f <<= 1;
        e--;
    }

    uint64_t biased_exponent = (e == kDenormalExponent && (f & kHiddenBit) == 0)
                               ? 0
                               : static_cast<uint64_t>(e + kExponentBias);

    uint64_t bits = (f & kSignificandMask) | (biased_exponent << kPhysicalSignificandSize);
    return reinterpret_bits<float>(static_cast<uint32_t>(bits));
}

static double make_double(uint64_t sign_bit, uint64_t biased_exponent, uint64_t significand)
{
    assert(sign_bit == 0 || sign_bit == 1);
    assert(biased_exponent <= 0x7FF);
    assert(significand <= 0x000FFFFFFFFFFFFF);

    uint64_t bits = 0;

    bits |= sign_bit << 63;
    bits |= biased_exponent << 52;
    bits |= significand;

    return reinterpret_bits<double>(bits);
}

// ldexp -- convert f * 2^e to IEEE double precision
static double make_double(uint64_t f, int e)
{
    constexpr uint64_t kHiddenBit               = 0x0010000000000000;
    constexpr uint64_t kSignificandMask         = 0x000FFFFFFFFFFFFF;
    constexpr int      kPhysicalSignificandSize = 52;  // Excludes the hidden bit.
    constexpr int      kExponentBias            = 0x3FF + kPhysicalSignificandSize;
    constexpr int      kDenormalExponent        = 1     - kExponentBias;
    constexpr int      kMaxExponent             = 0x7FF - kExponentBias;

    while (f > kHiddenBit + kSignificandMask)
    {
        f >>= 1;
        e++;
    }
    if (e >= kMaxExponent)
    {
        return std::numeric_limits<double>::infinity();
    }
    if (e < kDenormalExponent)
    {
        return 0.0;
    }
    while (e > kDenormalExponent && (f & kHiddenBit) == 0)
    {
        f <<= 1;
        e--;
    }

    uint64_t biased_exponent = (e == kDenormalExponent && (f & kHiddenBit) == 0)
                               ? 0
                               : static_cast<uint64_t>(e + kExponentBias);

    uint64_t bits = (f & kSignificandMask) | (biased_exponent << kPhysicalSignificandSize);
    return reinterpret_bits<double>(bits);
}

TEST_CASE("digit gen")
{
    SECTION("single precision")
    {
        auto check_float = [](float number, const std::string & digits, int expected_exponent)
        {
            CAPTURE(number);
            CAPTURE(digits);
            CAPTURE(expected_exponent);

            char buf[32];
            int len = 0;
            int exponent = 0;
            nlohmann::detail::dtoa_impl::grisu2(buf, len, exponent, number);

            CHECK(digits == std::string(buf, buf + len));
            CHECK(expected_exponent == exponent);
        };

        check_float(make_float(0,   0, 0x00000001),        "1", -45); // min denormal
        check_float(make_float(0,   0, 0x007FFFFF), "11754942", -45); // max denormal
        check_float(make_float(0,   1, 0x00000000), "11754944", -45); // min normal
        check_float(make_float(0,   1, 0x00000001), "11754945", -45);
        check_float(make_float(0,   1, 0x007FFFFF), "23509886", -45);
        check_float(make_float(0,   2, 0x00000000), "23509887", -45);
        check_float(make_float(0,   2, 0x00000001),  "2350989", -44);
        check_float(make_float(0,  24, 0x00000000), "98607613", -39); // fail if no special case in normalized boundaries
        check_float(make_float(0,  30, 0x00000000), "63108872", -37); // fail if no special case in normalized boundaries
        check_float(make_float(0,  31, 0x00000000), "12621775", -36); // fail if no special case in normalized boundaries
        check_float(make_float(0,  57, 0x00000000), "84703295", -29); // fail if no special case in normalized boundaries
        check_float(make_float(0, 254, 0x007FFFFE), "34028233",  31);
        check_float(make_float(0, 254, 0x007FFFFF), "34028235",  31); // max normal

        // V. Paxson and W. Kahan, "A Program for Testing IEEE Binary-Decimal Conversion", manuscript, May 1991,
        // ftp://ftp.ee.lbl.gov/testbase-report.ps.Z    (report)
        // ftp://ftp.ee.lbl.gov/testbase.tar.Z          (program)

        // Table 16: Stress Inputs for Converting 24-bit Binary to Decimal, < 1/2 ULP
        check_float(make_float(12676506, -102),       "25", -25);
        check_float(make_float(12676506, -103),      "125", -26);
        check_float(make_float(15445013,   86),     "1195",  30);
        check_float(make_float(13734123, -138),    "39415", -39);
        check_float(make_float(12428269, -130),   "913085", -38);
        check_float(make_float(15334037, -146),  "1719005", -43);
        check_float(make_float(11518287,  -41), "52379105", -13);
        check_float(make_float(12584953, -145),  "2821644", -43);
        check_float(make_float(15961084, -125), "37524328", -38);
        check_float(make_float(14915817, -146), "16721209", -44);
        check_float(make_float(10845484, -102), "21388946", -31);
        check_float(make_float(16431059,  -61),  "7125836", -18);

        // Table 17: Stress Inputs for Converting 24-bit Binary to Decimal, > 1/2 ULP
        check_float(make_float(16093626,   69),       "95",  26);
        check_float(make_float( 9983778,   25),      "335",  12);
        check_float(make_float(12745034,  104),     "2585",  35);
        check_float(make_float(12706553,   72),    "60005",  24);
        check_float(make_float(11005028,   45),   "387205",  15);
        check_float(make_float(15059547,   71),  "3555835",  22);
        check_float(make_float(16015691,  -99), "25268305", -30);
        check_float(make_float( 8667859,   56),  "6245851",  17);
        check_float(make_float(14855922,  -82), "30721327", -25);
        check_float(make_float(14855922,  -83), "15360663", -25);
        check_float(make_float(10144164, -110),   "781478", -32);
        check_float(make_float(13248074,   95), "52481028",  28);
    }

    SECTION("double precision")
    {
        auto check_double = [](double number, const std::string & digits, int expected_exponent)
        {
            CAPTURE(number);
            CAPTURE(digits);
            CAPTURE(expected_exponent);

            char buf[32];
            int len = 0;
            int exponent = 0;
            nlohmann::detail::dtoa_impl::grisu2(buf, len, exponent, number);

            CHECK(digits == std::string(buf, buf + len));
            CHECK(expected_exponent == exponent);
        };

        check_double(make_double(0,    0, 0x0000000000000001),                 "5", -324); // min denormal
        check_double(make_double(0,    0, 0x000FFFFFFFFFFFFF),  "2225073858507201", -323); // max denormal
        check_double(make_double(0,    1, 0x0000000000000000), "22250738585072014", -324); // min normal
        check_double(make_double(0,    1, 0x0000000000000001),  "2225073858507202", -323);
        check_double(make_double(0,    1, 0x000FFFFFFFFFFFFF), "44501477170144023", -324);
        check_double(make_double(0,    2, 0x0000000000000000),  "4450147717014403", -323);
        check_double(make_double(0,    2, 0x0000000000000001),  "4450147717014404", -323);
        check_double(make_double(0,    4, 0x0000000000000000), "17800590868057611", -323); // fail if no special case in normalized boundaries
        check_double(make_double(0,    5, 0x0000000000000000), "35601181736115222", -323); // fail if no special case in normalized boundaries
        check_double(make_double(0,    6, 0x0000000000000000),  "7120236347223045", -322); // fail if no special case in normalized boundaries
        check_double(make_double(0,   10, 0x0000000000000000), "11392378155556871", -321); // fail if no special case in normalized boundaries
        check_double(make_double(0, 2046, 0x000FFFFFFFFFFFFE), "17976931348623155",  292);
        check_double(make_double(0, 2046, 0x000FFFFFFFFFFFFF), "17976931348623157",  292); // max normal

        // Test different paths in DigitGen
        check_double(                  10000,                 "1",    4);
        check_double(                1200000,                "12",    5);
        check_double(4.9406564584124654e-324,                 "5", -324); // exit integral loop
        check_double(2.2250738585072009e-308,  "2225073858507201", -323); // exit fractional loop
        check_double(   1.82877982605164e-99,   "182877982605164", -113);
        check_double( 1.1505466208671903e-09, "11505466208671903",  -25);
        check_double( 5.5645893133766722e+20,  "5564589313376672",    5);
        check_double(     53.034830388866226, "53034830388866226",  -15);
        check_double(  0.0021066531670178605, "21066531670178605",  -19);

        // V. Paxson and W. Kahan, "A Program for Testing IEEE Binary-Decimal Conversion", manuscript, May 1991,
        // ftp://ftp.ee.lbl.gov/testbase-report.ps.Z    (report)
        // ftp://ftp.ee.lbl.gov/testbase.tar.Z          (program)

        // Table 3: Stress Inputs for Converting 53-bit Binary to Decimal, < 1/2 ULP
        check_double(make_double(8511030020275656,  -342) /*                9.5e-088 */,                "95",  -89);
        check_double(make_double(5201988407066741,  -824) /*               4.65e-233 */,               "465", -235);
        check_double(make_double(6406892948269899,  +237) /*              1.415e+087 */,              "1415",   84);
        check_double(make_double(8431154198732492,   +72) /*             3.9815e+037 */,             "39815",   33);
        check_double(make_double(6475049196144587,   +99) /*            4.10405e+045 */,            "410405",   40);
        check_double(make_double(8274307542972842,  +726) /*           2.920845e+234 */,           "2920845",  228);
        check_double(make_double(5381065484265332,  -456) /*          2.8919465e-122 */,          "28919465", -129);
        check_double(make_double(6761728585499734, -1057) /*         4.37877185e-303 */,         "437877185", -311);
        check_double(make_double(7976538478610756,  +376) /*        1.227701635e+129 */,        "1227701635",  120);
        check_double(make_double(5982403858958067,  +377) /*       1.8415524525e+129 */,       "18415524525",  119);
        check_double(make_double(5536995190630837,   +93) /*      5.48357443505e+043 */,      "548357443505",   32);
        check_double(make_double(7225450889282194,  +710) /*     3.891901811465e+229 */,     "3891901811465",  217);
        check_double(make_double(7225450889282194,  +709) /*    1.9459509057325e+229 */,    "19459509057325",  216);
        check_double(make_double(8703372741147379,  +117) /*   1.44609583816055e+051 */,   "144609583816055",   37);
        check_double(make_double(8944262675275217, -1001) /*  4.173677474585315e-286 */,  "4173677474585315", -301);
        check_double(make_double(7459803696087692,  -707) /* 1.1079507728788885e-197 */, "11079507728788885", -213);
        check_double(make_double(6080469016670379,  -381) /*  1.234550136632744e-099 */,  "1234550136632744", -114);
        check_double(make_double(8385515147034757,  +721) /* 9.2503171196036502e+232 */,   "925031711960365",  218);
        check_double(make_double(7514216811389786,  -828) /* 4.1980471502848898e-234 */,   "419804715028489", -248);
        check_double(make_double(8397297803260511,  -345) /* 1.1716315319786511e-088 */, "11716315319786511", -104);
        check_double(make_double(6733459239310543,  +202) /* 4.3281007284461249e+076 */,  "4328100728446125",   61);
        check_double(make_double(8091450587292794,  -473) /* 3.3177101181600311e-127 */,  "3317710118160031", -142);

        // Table 4: Stress Inputs for Converting 53-bit Binary to Decimal, > 1/2 ULP
        check_double(make_double(6567258882077402,  +952) /*                2.5e+302 */,                "25",  301);
        check_double(make_double(6712731423444934,  +535) /*               7.55e+176 */,               "755",  174);
        check_double(make_double(6712731423444934,  +534) /*              3.775e+176 */,              "3775",  173);
        check_double(make_double(5298405411573037,  -957) /*             4.3495e-273 */,             "43495", -277);
        check_double(make_double(5137311167659507,  -144) /*            2.30365e-028 */,            "230365",  -33);
        check_double(make_double(6722280709661868,  +363) /*           1.263005e+125 */,           "1263005",  119);
        check_double(make_double(5344436398034927,  -169) /*          7.1422105e-036 */,          "71422105",  -43);
        check_double(make_double(8369123604277281,  -853) /*         1.39345735e-241 */,         "139345735", -249);
        check_double(make_double(8995822108487663,  -780) /*        1.414634485e-219 */,        "1414634485", -228);
        check_double(make_double(8942832835564782,  -383) /*       4.5392779195e-100 */,       "45392779195", -110);
        check_double(make_double(8942832835564782,  -384) /*      2.26963895975e-100 */,      "226963895975", -111);
        check_double(make_double(8942832835564782,  -385) /*     1.134819479875e-100 */,     "1134819479875", -112);
        check_double(make_double(6965949469487146,  -249) /*    7.7003665618895e-060 */,    "77003665618895",  -73);
        check_double(make_double(6965949469487146,  -250) /*   3.85018328094475e-060 */,   "385018328094475",  -74);
        check_double(make_double(6965949469487146,  -251) /*  1.925091640472375e-060 */,  "1925091640472375",  -75);
        check_double(make_double(7487252720986826,  +548) /* 6.8985865317742005e+180 */, "68985865317742005",  164);
        check_double(make_double(5592117679628511,  +164) /* 1.3076622631878654e+065 */, "13076622631878654",   49);
        check_double(make_double(8887055249355788,  +665) /* 1.3605202075612124e+216 */, "13605202075612124",  200);
        check_double(make_double(6994187472632449,  +690) /* 3.5928102174759597e+223 */, "35928102174759597",  207);
        check_double(make_double(8797576579012143,  +588) /* 8.9125197712484552e+192 */,  "8912519771248455",  177);
        check_double(make_double(7363326733505337,  +272) /* 5.5876975736230114e+097 */, "55876975736230114",   81);
        check_double(make_double(8549497411294502,  -448) /* 1.1762578307285404e-119 */, "11762578307285404", -135);

        // Table 20: Stress Inputs for Converting 56-bit Binary to Decimal, < 1/2 ULP
        check_double(make_double(50883641005312716, -172) /* 8.4999999999999993e-036 */,  "8499999999999999",  -51);
        check_double(make_double(38162730753984537, -170) /* 2.5499999999999999e-035 */,               "255",  -37);
        check_double(make_double(50832789069151999, -101) /* 2.0049999999999997e-014 */, "20049999999999997",  -30);
        check_double(make_double(51822367833714164, -109) /* 7.9844999999999994e-017 */,  "7984499999999999",  -32);
        check_double(make_double(66840152193508133, -172) /* 1.1165499999999999e-035 */, "11165499999999999",  -51);
        check_double(make_double(55111239245584393, -138) /*           1.581615e-025 */,           "1581615",  -31);
        check_double(make_double(71704866733321482, -112) /*          1.3809855e-017 */,          "13809855",  -24);
        check_double(make_double(67160949328233173, -142) /* 1.2046404499999999e-026 */, "12046404499999999",  -42);
        check_double(make_double(53237141308040189, -152) /* 9.3251405449999991e-030 */,  "9325140544999999",  -45);
        check_double(make_double(62785329394975786, -112) /*       1.2092014595e-017 */,       "12092014595",  -27);
        check_double(make_double(48367680154689523,  -77) /* 3.2007045838499998e-007 */,      "320070458385",  -18);
        check_double(make_double(42552223180606797, -102) /*  8.391946324354999e-015 */,  "8391946324354999",  -30);
        check_double(make_double(63626356173011241, -112) /*    1.2253990460585e-017 */,    "12253990460585",  -30);
        check_double(make_double(43566388595783643,  -99) /* 6.8735641489760495e-014 */,   "687356414897605",  -28);
        check_double(make_double(54512669636675272, -159) /*  7.459816430480385e-032 */,  "7459816430480385",  -47);
        check_double(make_double(52306490527514614, -167) /* 2.7960588398142552e-034 */,  "2796058839814255",  -49);
        check_double(make_double(52306490527514614, -168) /* 1.3980294199071276e-034 */, "13980294199071276",  -50);
        check_double(make_double(41024721590449423,  -89) /* 6.6279012373057359e-011 */,  "6627901237305736",  -26);
        check_double(make_double(37664020415894738, -132) /* 6.9177880043968072e-024 */,  "6917788004396807",  -39);
        check_double(make_double(37549883692866294,  -93) /* 3.7915693108349708e-012 */,  "3791569310834971",  -27);
        check_double(make_double(69124110374399839, -104) /* 3.4080817676591365e-015 */, "34080817676591365",  -31);
        check_double(make_double(69124110374399839, -105) /* 1.7040408838295683e-015 */, "17040408838295683",  -31);

        // Table 21: Stress Inputs for Converting 56-bit Binary to Decimal, > 1/2 ULP
        check_double(make_double(49517601571415211,  -94) /* 2.4999999999999998e-012 */,                "25",  -13);
        check_double(make_double(49517601571415211,  -95) /* 1.2499999999999999e-012 */,               "125",  -14);
        check_double(make_double(54390733528642804, -133) /* 4.9949999999999996e-024 */, "49949999999999996",  -40); // shortest: 4995e-27
        check_double(make_double(71805402319113924, -157) /* 3.9304999999999998e-031 */, "39304999999999998",  -47); // shortest: 39305e-35
        check_double(make_double(40435277969631694, -179) /* 5.2770499999999992e-038 */,  "5277049999999999",  -53);
        check_double(make_double(57241991568619049, -165) /*           1.223955e-033 */,           "1223955",  -39);
        check_double(make_double(65224162876242886,  +58) /* 1.8799584999999998e+034 */, "18799584999999998",   18);
        check_double(make_double(70173376848895368, -138) /*         2.01387715e-025 */,         "201387715",  -33);
        check_double(make_double(37072848117383207,  -99) /* 5.8490641049999989e-014 */,  "5849064104999999",  -29);
        check_double(make_double(56845051585389697, -176) /* 5.9349003054999999e-037 */,       "59349003055",  -47);
        check_double(make_double(54791673366936431, -145) /* 1.2284718039499998e-027 */, "12284718039499998",  -43);
        check_double(make_double(66800318669106231, -169) /* 8.9270767180849991e-035 */,  "8927076718084999",  -50);
        check_double(make_double(66800318669106231, -170) /* 4.4635383590424995e-035 */, "44635383590424995",  -51);
        check_double(make_double(66574323440112438, -119) /* 1.0016990862549499e-019 */, "10016990862549499",  -35);
        check_double(make_double(65645179969330963, -173) /* 5.4829412628024647e-036 */,  "5482941262802465",  -51);
        check_double(make_double(61847254334681076, -109) /* 9.5290783281036439e-017 */,  "9529078328103644",  -32);
        check_double(make_double(39990712921393606, -145) /* 8.9662279366405553e-028 */,  "8966227936640555",  -43);
        check_double(make_double(59292318184400283, -149) /* 8.3086234418058538e-029 */,  "8308623441805854",  -44);
        check_double(make_double(69116558615326153, -143) /* 6.1985873566126555e-027 */, "61985873566126555",  -43);
        check_double(make_double(69116558615326153, -144) /* 3.0992936783063277e-027 */, "30992936783063277",  -43);
        check_double(make_double(39462549494468513, -152) /* 6.9123512506176015e-030 */,  "6912351250617602",  -45);
        check_double(make_double(39462549494468513, -153) /* 3.4561756253088008e-030 */,  "3456175625308801",  -45);
    }
}

TEST_CASE("formatting")
{
    SECTION("single precision")
    {
        auto check_float = [](float number, const std::string & expected)
        {
            char buf[32];
            char* end = nlohmann::detail::to_chars(buf, buf + 32, number);
            std::string actual(buf, end);

            CHECK(actual == expected);
        };
        // %.9g
        check_float( -1.2345e-22f, "-1.2345e-22"  ); // -1.23450004e-22
        check_float( -1.2345e-21f, "-1.2345e-21"  ); // -1.23450002e-21
        check_float( -1.2345e-20f, "-1.2345e-20"  ); // -1.23450002e-20
        check_float( -1.2345e-19f, "-1.2345e-19"  ); // -1.23449999e-19
        check_float( -1.2345e-18f, "-1.2345e-18"  ); // -1.23449996e-18
        check_float( -1.2345e-17f, "-1.2345e-17"  ); // -1.23449998e-17
        check_float( -1.2345e-16f, "-1.2345e-16"  ); // -1.23449996e-16
        check_float( -1.2345e-15f, "-1.2345e-15"  ); // -1.23450002e-15
        check_float( -1.2345e-14f, "-1.2345e-14"  ); // -1.23450004e-14
        check_float( -1.2345e-13f, "-1.2345e-13"  ); // -1.23449997e-13
        check_float( -1.2345e-12f, "-1.2345e-12"  ); // -1.23450002e-12
        check_float( -1.2345e-11f, "-1.2345e-11"  ); // -1.2345e-11
        check_float( -1.2345e-10f, "-1.2345e-10"  ); // -1.2345e-10
        check_float( -1.2345e-9f,  "-1.2345e-09"  ); // -1.23449995e-09
        check_float( -1.2345e-8f,  "-1.2345e-08"  ); // -1.23449997e-08
        check_float( -1.2345e-7f,  "-1.2345e-07"  ); // -1.23449993e-07
        check_float( -1.2345e-6f,  "-1.2345e-06"  ); // -1.23450002e-06
        check_float( -1.2345e-5f,  "-1.2345e-05"  ); // -1.2345e-05
        check_float( -1.2345e-4f,  "-0.00012345"  ); // -0.000123449994
        check_float( -1.2345e-3f,  "-0.0012345"   ); // -0.00123449997
        check_float( -1.2345e-2f,  "-0.012345"    ); // -0.0123450002
        check_float( -1.2345e-1f,  "-0.12345"     ); // -0.123450004
        check_float( -0.0f,        "-0.0"         ); // -0
        check_float(  0.0f,         "0.0"         ); //  0
        check_float(  1.2345e+0f,   "1.2345"      ); //  1.23450005
        check_float(  1.2345e+1f,   "12.345"      ); //  12.3450003
        check_float(  1.2345e+2f,   "123.45"      ); //  123.449997
        check_float(  1.2345e+3f,   "1234.5"      ); //  1234.5
        check_float(  1.2345e+4f,   "12345.0"     ); //  12345
        check_float(  1.2345e+5f,   "123450.0"    ); //  123450
        check_float(  1.2345e+6f,   "1.2345e+06"  ); //  1234500
        check_float(  1.2345e+7f,   "1.2345e+07"  ); //  12345000
        check_float(  1.2345e+8f,   "1.2345e+08"  ); //  123450000
        check_float(  1.2345e+9f,   "1.2345e+09"  ); //  1.23449997e+09
        check_float(  1.2345e+10f,  "1.2345e+10"  ); //  1.23449999e+10
        check_float(  1.2345e+11f,  "1.2345e+11"  ); //  1.23449999e+11
        check_float(  1.2345e+12f,  "1.2345e+12"  ); //  1.23450006e+12
        check_float(  1.2345e+13f,  "1.2345e+13"  ); //  1.23449995e+13
        check_float(  1.2345e+14f,  "1.2345e+14"  ); //  1.23450002e+14
        check_float(  1.2345e+15f,  "1.2345e+15"  ); //  1.23450003e+15
        check_float(  1.2345e+16f,  "1.2345e+16"  ); //  1.23449998e+16
        check_float(  1.2345e+17f,  "1.2345e+17"  ); //  1.23449996e+17
        check_float(  1.2345e+18f,  "1.2345e+18"  ); //  1.23450004e+18
        check_float(  1.2345e+19f,  "1.2345e+19"  ); //  1.23449999e+19
        check_float(  1.2345e+20f,  "1.2345e+20"  ); //  1.23449999e+20
        check_float(  1.2345e+21f,  "1.2345e+21"  ); //  1.23449999e+21
        check_float(  1.2345e+22f,  "1.2345e+22"  ); //  1.23450005e+22
    }

    SECTION("double precision")
    {
        auto check_double = [](double number, const std::string & expected)
        {
            char buf[32];
            char* end = nlohmann::detail::to_chars(buf, buf + 32, number);
            std::string actual(buf, end);

            CHECK(actual == expected);
        };
        //                           dtoa                           %.15g                     %.17g                     shortest
        check_double( -1.2345e-22,  "-1.2345e-22"             ); // -1.2345e-22               -1.2345000000000001e-22   -1.2345e-22
        check_double( -1.2345e-21,  "-1.2345e-21"             ); // -1.2345e-21               -1.2345000000000001e-21   -1.2345e-21
        check_double( -1.2345e-20,  "-1.2345e-20"             ); // -1.2345e-20               -1.2345e-20               -1.2345e-20
        check_double( -1.2345e-19,  "-1.2345e-19"             ); // -1.2345e-19               -1.2345000000000001e-19   -1.2345e-19
        check_double( -1.2345e-18,  "-1.2345e-18"             ); // -1.2345e-18               -1.2345000000000001e-18   -1.2345e-18
        check_double( -1.2345e-17,  "-1.2345e-17"             ); // -1.2345e-17               -1.2345e-17               -1.2345e-17
        check_double( -1.2345e-16,  "-1.2345e-16"             ); // -1.2345e-16               -1.2344999999999999e-16   -1.2345e-16
        check_double( -1.2345e-15,  "-1.2345e-15"             ); // -1.2345e-15               -1.2345e-15               -1.2345e-15
        check_double( -1.2345e-14,  "-1.2345e-14"             ); // -1.2345e-14               -1.2345e-14               -1.2345e-14
        check_double( -1.2345e-13,  "-1.2345e-13"             ); // -1.2345e-13               -1.2344999999999999e-13   -1.2345e-13
        check_double( -1.2345e-12,  "-1.2345e-12"             ); // -1.2345e-12               -1.2345e-12               -1.2345e-12
        check_double( -1.2345e-11,  "-1.2345e-11"             ); // -1.2345e-11               -1.2345e-11               -1.2345e-11
        check_double( -1.2345e-10,  "-1.2345e-10"             ); // -1.2345e-10               -1.2345e-10               -1.2345e-10
        check_double( -1.2345e-9,   "-1.2345e-09"             ); // -1.2345e-09               -1.2345e-09               -1.2345e-9
        check_double( -1.2345e-8,   "-1.2345e-08"             ); // -1.2345e-08               -1.2345000000000001e-08   -1.2345e-8
        check_double( -1.2345e-7,   "-1.2345e-07"             ); // -1.2345e-07               -1.2345000000000001e-07   -1.2345e-7
        check_double( -1.2345e-6,   "-1.2345e-06"             ); // -1.2345e-06               -1.2345e-06               -1.2345e-6
        check_double( -1.2345e-5,   "-1.2345e-05"             ); // -1.2345e-05               -1.2345e-05               -1.2345e-5
        check_double( -1.2345e-4,   "-0.00012345"             ); // -0.00012345               -0.00012344999999999999   -0.00012345
        check_double( -1.2345e-3,   "-0.0012345"              ); // -0.0012345                -0.0012344999999999999    -0.0012345
        check_double( -1.2345e-2,   "-0.012345"               ); // -0.012345                 -0.012345                 -0.012345
        check_double( -1.2345e-1,   "-0.12345"                ); // -0.12345                  -0.12345                  -0.12345
        check_double( -0.0,         "-0.0"                    ); // -0                        -0                        -0
        check_double(  0.0,          "0.0"                    ); //  0                         0                         0
        check_double(  1.2345e+0,    "1.2345"                 ); //  1.2345                    1.2344999999999999        1.2345
        check_double(  1.2345e+1,    "12.345"                 ); //  12.345                    12.345000000000001        12.345
        check_double(  1.2345e+2,    "123.45"                 ); //  123.45                    123.45                    123.45
        check_double(  1.2345e+3,    "1234.5"                 ); //  1234.5                    1234.5                    1234.5
        check_double(  1.2345e+4,    "12345.0"                ); //  12345                     12345                     12345
        check_double(  1.2345e+5,    "123450.0"               ); //  123450                    123450                    123450
        check_double(  1.2345e+6,    "1234500.0"              ); //  1234500                   1234500                   1234500
        check_double(  1.2345e+7,    "12345000.0"             ); //  12345000                  12345000                  12345000
        check_double(  1.2345e+8,    "123450000.0"            ); //  123450000                 123450000                 123450000
        check_double(  1.2345e+9,    "1234500000.0"           ); //  1234500000                1234500000                1234500000
        check_double(  1.2345e+10,   "12345000000.0"          ); //  12345000000               12345000000               12345000000
        check_double(  1.2345e+11,   "123450000000.0"         ); //  123450000000              123450000000              123450000000
        check_double(  1.2345e+12,   "1234500000000.0"        ); //  1234500000000             1234500000000             1234500000000
        check_double(  1.2345e+13,   "12345000000000.0"       ); //  12345000000000            12345000000000            12345000000000
        check_double(  1.2345e+14,   "123450000000000.0"      ); //  123450000000000           123450000000000           123450000000000
        check_double(  1.2345e+15,   "1.2345e+15"             ); //  1.2345e+15                1234500000000000          1.2345e15
        check_double(  1.2345e+16,   "1.2345e+16"             ); //  1.2345e+16                12345000000000000         1.2345e16
        check_double(  1.2345e+17,   "1.2345e+17"             ); //  1.2345e+17                1.2345e+17                1.2345e17
        check_double(  1.2345e+18,   "1.2345e+18"             ); //  1.2345e+18                1.2345e+18                1.2345e18
        check_double(  1.2345e+19,   "1.2345e+19"             ); //  1.2345e+19                1.2345e+19                1.2345e19
        check_double(  1.2345e+20,   "1.2345e+20"             ); //  1.2345e+20                1.2345e+20                1.2345e20
        check_double(  1.2345e+21,   "1.2344999999999999e+21" ); //  1.2345e+21                1.2344999999999999e+21    1.2345e21
        check_double(  1.2345e+22,   "1.2345e+22"             ); //  1.2345e+22                1.2345e+22                1.2345e22
    }
}