ieee 浮動小数点例外モードを設定

## 呼出し手順

                mod = ieee()
                ieee(mod)

## 引数

mod

  整数スカラーで,0,1または2を指定

## 説明

`ieee()` はカレントの浮動小数点例外モード を返します.

0

  浮動小数点例外はエラーを発生

  `%inf` and `%nan` special values can be used in this mode without error. For instance, `%inf/%inf`, `%inf-%inf` or `%inf/%nan` are known operations.

1
  浮動小数点例外は警告を発生.
2
  浮動小数点例外は無限大(Inf)またはNaNを発生.

`ieee(mod)` sets the current floating point exception mode to `mod`.

The default initial mode is 2. This default value may be set in any of the following ways:

- Through the Preferences GUI: `preferences`, in the section General => Environment => ieee.
- Equivalently, using `xmlSetValues` as follows (to set the mode to 1) :

  `xmlSetValues("//general/body/environment", ["fpe";"1"])`

- Or by using `ieee(mod)` in your startup file.

ライブラリのアルゴリズムの内部で発生した浮動小数点例外は, まだ`ieee`モードでは設定できません.

## 例

    ieee(1); 1/0
    ieee(2); 1/0, log(0)

## 参照

- %nan
- %inf
- isinf
- isnan
- number_properties

## 履歴

6.0.0 2 is now the initial mode value.