[erlang-questions] convert strings like "1e-8" to floats.
Wed Feb 8 16:42:07 CET 2017
Both the NNN_NNN and the Base#NNN notation go back to Ada, so they are not
particular either for OCaml or Erlang, respectively.
2017-02-08 16:35 GMT+01:00 Jesper Louis Andersen <
> Another example is OCaml, which supports entering integers as
> # 1_000_000;;
> - : int = 1000000
> which is very nifty, but unique to OCaml and thus not too portable.
> On Wed, Feb 8, 2017 at 12:16 PM Mikael Pettersson <>
>> Oleksii Semilietov writes:
>> > Hi all!
>> > I playing with converting binaries and lists to floats and I found
>> > something what I can't solve via elegant way. I believe it's my
>> leakage of
>> > understanding floats.
>> > So, what is different between 1e-8 and 1.0e-8 ?
>> > For example we have float as list "0.01". It is easy to convert it to
>> > float just via list_to_float("0.01").
>> > But when floats coming from external world as binaries or lists which
>> > like "1e-8", and not like "1.0e-8", I can't find proper way to convert
>> > For example in PHP both 1e-8 and 1.0e-8 is equivalent
>> > var_dump(floatval("1e-8") === floatval("1.0e-8")) returns true.
>> > In Erlang
>> > list_to_float("1.0E-8") =:= 0.00000001
>> > true
>> > but
>> > list_to_float("1E-8") =:= 0.00000001.
>> > ** exception error: bad argument in function list_to_float/1 called as
>> > list_to_float("1E-8")
>> > How to convert it via right way?
>> Write your own conversion routine.
>> Your mistake is assuming literals like floats have the same look and feel
>> regardless of language or environment. That's in general not true.
>> You may also consider the different notation for integers with non-decimal
>> base, e.g. 0xabba vs 16#abba, or character literals, etc.
>> What it means is that a tool written in one language but processing source
>> code for another, must be prepared to do all conversions on its own
>> relying on ready-made services in the implementation language.
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