From ab27e8699ef2a2bafe574158200993f184de3dc2 Mon Sep 17 00:00:00 2001 From: Serge Aleynikov Date: Mon, 21 Jan 2013 15:36:43 +0100 Subject: Text representation of a float formatted using given options. This BIF solves a problem of float_to_list/1 that doesn't allow specifying the number of digits after the decimal point when formatting floats. float_to_list(Float, Options) -> string() Float = float() Options = [Option] Option = {decimals, Decimals::0..249} | {scientific, Decimals::0..249} | compact Returns a string which corresponds to the text representation of a `Float` formatted using given options. When decimals option is specified the returned value will contain at most `Decimals` number of digits past the decimal point. When `compact` option is provided the trailing zeros at the end of the list are truncated (this option is only meaningful together with the `decimals` option). When `scientific` option is provided, the float will be formatted using scientific notation with `Decimals` digits of precision. If `Options` is `[]` the function behaves like `float_to_list/1`. When using `decimals` option and the number doesn't fit in the static internal buffer of 256 bytes the function throws `badarg`. --- erts/emulator/test/num_bif_SUITE.erl | 45 +++++++++++++++++++++++++++++++----- 1 file changed, 39 insertions(+), 6 deletions(-) (limited to 'erts/emulator/test') diff --git a/erts/emulator/test/num_bif_SUITE.erl b/erts/emulator/test/num_bif_SUITE.erl index 4459732257..7a045484cf 100644 --- a/erts/emulator/test/num_bif_SUITE.erl +++ b/erts/emulator/test/num_bif_SUITE.erl @@ -25,6 +25,7 @@ %% abs/1 %% float/1 %% float_to_list/1 +%% float_to_list/2 %% integer_to_list/1 %% list_to_float/1 %% list_to_integer/1 @@ -114,14 +115,46 @@ t_float(Config) when is_list(Config) -> ok. -%% Tests float_to_list/1. +%% Tests float_to_list/1, float_to_list/2. t_float_to_list(Config) when is_list(Config) -> - ?line test_ftl("0.0e+0", 0.0), - ?line test_ftl("2.5e+1", 25.0), - ?line test_ftl("2.5e+0", 2.5), - ?line test_ftl("2.5e-1", 0.25), - ?line test_ftl("-3.5e+17", -350.0e15), + test_ftl("0.0e+0", 0.0), + test_ftl("2.5e+1", 25.0), + test_ftl("2.5e+0", 2.5), + test_ftl("2.5e-1", 0.25), + test_ftl("-3.5e+17", -350.0e15), + "1.00000000000000000000e+00" = float_to_list(1.0), + "1.00000000000000000000e+00" = float_to_list(1.0, []), + "-1.00000000000000000000e+00" = float_to_list(-1.0, []), + "-1.00000000000000000000" = float_to_list(-1.0, [{decimals, 20}]), + {'EXIT', {badarg, _}} = (catch float_to_list(1.0, [{decimals, -1}])), + {'EXIT', {badarg, _}} = (catch float_to_list(1.0, [{decimals, 250}])), + {'EXIT', {badarg, _}} = (catch float_to_list(1.0e+300, [{decimals, 1}])), + "1.0e+300" = float_to_list(1.0e+300, [{scientific, 1}]), + "1.0" = float_to_list(1.0, [{decimals, 249}, compact]), + Expected = "1." ++ string:copies("0", 249) ++ "e+00", + Expected = float_to_list(1.0, [{scientific, 249}, compact]), + + X1 = float_to_list(1.0), + X2 = float_to_list(1.0, [{scientific, 20}]), + X1 = X2, + "1.000e+00" = float_to_list(1.0, [{scientific, 3}]), + "1.000" = float_to_list(1.0, [{decimals, 3}]), + "1.0" = float_to_list(1.0, [{decimals, 3}, compact]), + "1.12" = float_to_list(1.123, [{decimals, 2}]), + "1.123" = float_to_list(1.123, [{decimals, 3}]), + "1.123" = float_to_list(1.123, [{decimals, 3}, compact]), + "1.1230" = float_to_list(1.123, [{decimals, 4}]), + "1.12300" = float_to_list(1.123, [{decimals, 5}]), + "1.123" = float_to_list(1.123, [{decimals, 5}, compact]), + "1.1234" = float_to_list(1.1234,[{decimals, 6}, compact]), + "2.333333" = erlang:float_to_list(7/3, [{decimals, 6}, compact]), + "2.333333" = erlang:float_to_list(7/3, [{decimals, 6}]), + "0.00000000000000000000e+00" = float_to_list(0.0, [compact]), + "0.0" = float_to_list(0.0, [{decimals, 10}, compact]), + "123000000000000000000.0" = float_to_list(1.23e20, [{decimals, 10}, compact]), + "1.2300000000e+20" = float_to_list(1.23e20, [{scientific, 10}, compact]), + "1.23000000000000000000e+20" = float_to_list(1.23e20, []), ok. test_ftl(Expect, Float) -> -- cgit v1.2.3