josdejong
commented
8 years ago Do I summarize your story correctly if you would like to be able to define
{exponential: {lower: -Infinity, upper: Infinity}}? That makes sense.
The lower and upper configuration expects a value, not an exponent. The following works as expected:
var numbers = [
1.1234567890123456789e+30,
1.1234567890123456789e-30,
-1.1234567890123456789e+30,
-1.1234567890123456789e-30,
math.bignumber("0.12345678901234567890123456789012345678901234567890123456789012345678901234567890"),
math.bignumber("12345678901234567890123456789012345678901234567890123456789012345678901234567890")]
var i;
for (i=0;i<numbers.length;i++) {
console.log(math.format(numbers[i],{exponential:{lower:1e-100,upper:1e100}}));
}outputs:
1123456789012345700000000000000
0.0000000000000000000000000000011234567890123457
-1123456789012345700000000000000
-0.0000000000000000000000000000011234567890123457
0.1234567890123456789012345678901234567890123456789012345678901235
12345678901234567890123456789012345678901234567890123456789012350000000000000000
balagge
mirabilos
zohaibtahir
I have a scenario where I need a string representation of a number without exponential notation (i.e. always in "normal" decimal notation). No rounding should occur, and the actual (highest available) precision value is required. Also, no unnecessary trailing zeros after the decimal point, please :)
Now this is crazily difficult in plain javascript, as far as I know there is no simple solution for that. See this mess:
http://stackoverflow.com/questions/1685680/how-to-avoid-scientific-notation-for-large-numbers-in-javascript
I checked
math.format, but, unfortunately, it copies the behavior of javascriptNumber.prototype.toFixed(), in the sense that specifyingnotation:"fixed"will always require an actualprecisionsetting (if omitted, defaulted to zero), which is unfortunate, because it causes rounding and/or adding unnecessary 0's after the last significant digit after the decimal point. So, at the end of the day, it returns a different or non-canonical string representation of the input number. By the way,toFixed()does not deliver its promise even in the sense that it returns exponential notation sometimes (???!!). So again,toFixed()is pretty useless, and, by copying its behavior,math.format()also seems pretty useless.Then I realized that I can solve the problem by using
notation:"auto"(which is the default) because it allows the additional optionexponentialand I can setexponential:{lower:0, upper:Infinity}. This does the job nicely! No rounding, no unnecessary zeroes added!However, when I use the same function for decimals (bignumbers), a run-time exception occurs.
I checked the source and I found this (lib/utils/bignumber/formatter.js, lines 118-126):
This is where the exception occurs, because the
value.constructor.toExpNegandvalue.constructor.toExpPosdo not accept values-InfinitiyandInfinity, respectively (where-Infinity = Math.log(0), andInfinity = Math.log(Infinity).However, the lines above are not needed at all, since
oldConfigis not referenced in the source at all, and setting thetoExpNegandtoExpPosproperties is not required on the constructor (as far as I see), since the following lines (134-141) check the limits for exponential notation, and it is notdecimal.jsthat decides whether to use exponential or fixed notation.So I tried removing the above lines, and everything works as expected! Try:
with the above lines this produces an exception.
Error: [DecimalError] Invalid argument: toExpNeg: -Infinitywithout them, it produces the expected results:
Note: loss of some significant digits is normal, both for the javascript numbers (float) and for the decimals (precision is set to 64 significant digits).
So maybe removing lines 118 through 126 from formatter.js could be a solution? But I kind of hesitate, because of a comment in the source (line 117):
So maybe I am missing a point here?
Update: checked for complexes as well, the setting
{exponential:{lower:0,upper:Infinity}}works fine, also!Update2: decimal.js does correct the messy behavior of javascript
toFixed(), it drops both the (stupid) defaulting of precision to 0, and the (even crazier) exponential notation in the return value. Seehttp://mikemcl.github.io/decimal.js/#toFixed
Where it reads
" Unlike Number.prototype.toFixed, which returns exponential notation if a number is greater or equal to 10^21, this method will always return normal notation.
If dp is omitted, the return value will be unrounded and in normal notation. This is unlike Number.prototype.toFixed, which returns the value to zero decimal places[...]"