Search code examples
juliascientific-notation

string to integer in scientific notation

What is the canonical way of converting a string storing a number in scientific notation into an integer?

from

"1e6"

to

1000000

As for the reverse process, converting integer to string in scientific notation I understand I can use @sprintf macro. If one knows the exact format to achieve exactly the reverse process - so small e and no extra trailing .00 zeros (like 1.00e6), or leading zeros (like 1e08) - I will appreciate if it will be included for completeness.

Solution

  • The conversion from string to integer can be achieved via floats like this:

    julia> Int(parse(Float64, "1e6"))
1000000

    if you know that the number will fit into Int64 or like this

    julia> BigInt(parse(BigFloat, "1e6"))
1000000

    for larger numbers.

    For the reverse process the default in @sprintf would be the following:

    julia> @sprintf("%.0e", 1_000_000)
"1e+06"

    However, you get + after e and at least two digits are displayed in the exponent (both features are a standard to expect across different languages when you do such a conversion). Also note that this process will lead to rounding, e.g.:

    julia> @sprintf("%.0e", 1_000_001)
"1e+06"