Get a single float value from a string in elixir

Question

Is there a method that takes in a float string and converts it to a single float. It must also handle strings without . like "1"

String.to_float does not handle "1"

iex(5)> String.to_float("1")
** (ArgumentError) argument error
:erlang.binary_to_float("1")
iex(5)> String.to_float("1.0")
1.0

Float.parse handles "1", but returns a tuple.

iex(4)> Float.parse("1")
{1.0, ""}

The tuple is so it can return the float that it parsed, and the remainder of the string that it didn't know what to do with. That is expected with a parser. Just use the first value from the tuple. Or create a wrapper function if you plan on doing it a lot and don't care for the remainder string. — Justin Wood
– Justin Wood, Commented Dec 4, 2016 at 12:52

Community · Accepted Answer · 2017-05-23 10:30:11Z

3

Convert Elixir string to integer or float

Maybe you should use something like

{res, _} = Float.parse("1")

or

elem Float.parse("1"), 0

edited May 23, 2017 at 10:30

CommunityBot

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answered Dec 4, 2016 at 14:48

Artyom Malyshev

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5 Comments

Patrick Oscity Over a year ago

It might be helpful to know why the second element of the tuple can be discarded here.

Artyom Malyshev Over a year ago

iex(1)> Float.parse("56.5xyz") {56.5, "xyz"}

helios35 Over a year ago

I'd prefer to use {res, ""} = Float.parse(float_as_string) if float_as_string is not expected to have trailing rest. This way, the code fails fast if your assumption is not met.

toftis Over a year ago

Do you know why String.to_float("1") is not working?

Rafa Paez Over a year ago

As per the documentation, String.to_float: string must be the string representation of a float (Remember that Floating-point numbers must have at least one digit before and after the decimal point). If a string representation of an integer wants to be used, then Float.parse/1 should be used instead, otherwise an argument error will be raised.

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