Is that a json api? If so you’d need to look into your json libraries encoding function. But in the end if you’re not formatting as a string there’s likely no difference. Unless the other end parses the float number back into a decimal, but again into a float value it’ll always become 1.0. Floats do not explicitly store decimal points and when the binary float format is converted to a string for inspection it’s just printed with the least amout of decimal points.

Floats are not actually stored as 1.0 and so on, they have a different internal representation.

Can you explain what it is you’re trying to accomplish?

Okay, so the actual question is “how do I get the JSON encoder to format floats with extra precision”. We don’t know what JSON library you’re using, but the Erlang :json just calls float_to_binary. It looks like the encoder function can be overridden, so you could provide one that encodes floats with extra zeros if you like.

However, as suggested above this is probably a waste of time. The consumer of the API should just decode the value back into a float, in which case it won’t matter. But if you have some weird requirement for this behavior, that’s how you would do it.

It’s also worth remembering that JSON doesn’t have an integer or float type, only numbers. Different JSON libraries handle numbers in different ways. For example, golang treats all JSON numbers as floats by default (even when the number doesn’t have a decimal point). So, it’s undefined what will happen to precision when you send a number over JSON.

You will need something that will format your floats. The Number library does this.