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Rewrite the float-to-string conversion

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Instead of committing to a number of decimal places, the new algorithm targets a certain number of significant digits.
Since the mantissa has to fit in a 32-bit integer, the number of significant digits is limited to 9.
This commit is contained in:
Benoit Blanchon
2025-10-28 19:24:03 +01:00
parent 6cc8b313ed
commit 9bfa11387d
4 changed files with 84 additions and 66 deletions
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26
extras/tests/TextFormatter/writeFloat.cpp
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@@ -24,7 +24,7 @@ static std::string toString(TFloat input) {
TEST_CASE("TextFormatter::writeFloat(double)") {
SECTION("Pi") {
REQUIRE(toString(3.14159265359) == "3.141592654");
REQUIRE(toString(3.14159265359) == "3.14159265");
}
SECTION("Signaling NaN") {
@@ -49,13 +49,13 @@ TEST_CASE("TextFormatter::writeFloat(double)") {
}
SECTION("Espilon") {
REQUIRE(toString(2.2250738585072014E-308) == "2.225073859e-308");
REQUIRE(toString(-2.2250738585072014E-308) == "-2.225073859e-308");
REQUIRE(toString(2.2250738585072014E-308) == "2.22507386e-308");
REQUIRE(toString(-2.2250738585072014E-308) == "-2.22507386e-308");
}
SECTION("Max double") {
REQUIRE(toString(1.7976931348623157E+308) == "1.797693135e308");
REQUIRE(toString(-1.7976931348623157E+308) == "-1.797693135e308");
REQUIRE(toString(1.7976931348623157E+308) == "1.79769313e308");
REQUIRE(toString(-1.7976931348623157E+308) == "-1.79769313e308");
}
SECTION("Big exponent") {
@@ -72,10 +72,10 @@ TEST_CASE("TextFormatter::writeFloat(double)") {
}
SECTION("Exponentation when >= 1e7") {
REQUIRE(toString(9999999.999) == "9999999.999");
REQUIRE(toString(9999999.99) == "9999999.99");
REQUIRE(toString(10000000.0) == "1e7");
REQUIRE(toString(-9999999.999) == "-9999999.999");
REQUIRE(toString(-9999999.99) == "-9999999.99");
REQUIRE(toString(-10000000.0) == "-1e7");
}
@@ -85,12 +85,20 @@ TEST_CASE("TextFormatter::writeFloat(double)") {
REQUIRE(toString(0.9999999996) == "1");
}
SECTION("9 decimal places") {
REQUIRE(toString(0.10000001) == "0.10000001");
REQUIRE(toString(0.99999999) == "0.99999999");
REQUIRE(toString(9.00000001) == "9.00000001");
REQUIRE(toString(9.99999999) == "9.99999999");
}
SECTION("9 decimal places") {
REQUIRE(toString(0.100000001) == "0.100000001");
REQUIRE(toString(0.999999999) == "0.999999999");
REQUIRE(toString(9.000000001) == "9.000000001");
REQUIRE(toString(9.999999999) == "9.999999999");
REQUIRE(toString(9.000000001) == "9");
REQUIRE(toString(9.999999999) == "10");
}
SECTION("10 decimal places") {