Question

I do this operation and I want result without exponents :

main(){
  var result = ((1.1+2)+3.14+4+(5+6+7)+(8+9+10)*4267387833344334647677634)/2*553344300034334349999000;
  print(result); // With exponent
  print(result.toInt()); // Full number ?
}

And it print

3.18780189038289e+49
31878018903828901761984975061078744643351263313920

But the toInt() result is wrong, the good result is 31878018903828899277492024491376690701584023926880 . It check it with groovy (web) console.
How can I do to have my int full number ?

Answer 1

As in result there are double literals, the result type is double.

In Dart a double is a :

64-bit (double-precision) floating-point numbers, as specified by the IEEE 754 standard

This is why you lose precision.

You can see the lost of precision with the following code :

final bignum = 31878018903828899277492024491376690701584023926880;
print(bignum);
// displays 31878018903828899277492024491376690701584023926880
print(bignum.toDouble().toInt());
// displays 31878018903828901761984975061078744643351263313920

This lost of precision is not specific to Dart, for instance 31878018903828899277492024491376690701584023926880.0 and 31878018903828901761984975061078744643351263313920.0 are equal in Java.

The groovy web console gives you the right result because AFAICT groovy literals with decimal points are instantiated as java.math.BigDecimal by default.

Finally there is an open issue on Decimal data type you can star and until decimals are natively supported, you can use my decimal package;