Truncate a float in Erlang

Question

I am using a function to create a list from a float.

 float_to_list(0.02).

It returns:

\"2.00000000000000000000e-002\"


        

Answer 1

Are you looking for something like this:

6> F = 5/2.
2.50000
7> io_lib:format("~.1f",[F]).
["2.5"]
8> io_lib:format("~.2f",[F]).
["2.50"]
9> io_lib:format("~.3f",[F]).
["2.500"]

if yes, have a look at the module io_lib.

Answer 2

I know people don't like the, "I am not an expert in language X" answers, but the printf command is quite ubiquitous so I will say, look for an analog of printf in Erlang.

Edit: It looks like the format and fwrite may be those analogs. For more info from erlang.org.

Answer 3

This link provides functions that truncate/floor or ceil or round a float. Given those you can round to 2 digits by multiplying by 100, rounging and then dividing back by 100 (and possibly rounding again to avoid precision errors)

Answer 4

mochinum:digits converts a float to a string with an appropriate level of precision.

1> mochinum:digits(1.1).
"1.1"
2> mochinum:digits(1.2345).
"1.2345"

Not exactly what the OP requested, but useful nonetheless.

Answer 5

Alternatively you could use the function you were already using.

float_to_list(0.02,[{decimals, 2}]) outputs '0.02'

Or for Elixir users ;)

:erlang.float_to_list(5.231,[{:decimals, 2}]) outputs '5.2'