Difference between revisions of "SetRoundMode"
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| − | With | + | With {{Doc|package=RTL|unit=math|identifier=setroundmode|text=<syntaxhighlight lang="pascal" inline>math.setRoundMode</syntaxhighlight>}} you can set the <abbr title="Floating Point Unit">FPU</abbr>’s method of rounding. |
| + | If no FPU is present, the global variable {{Doc|package=RTL|unit=system|identifier=softfloat_rounding_mode|text=<syntaxhighlight lang="pascal" inline>system.softFloat_rounding_mode</syntaxhighlight>}} will determine the rounding mode for floating-point operations implemented by software. | ||
| − | + | This also affects the run-time behavior of the <syntaxhighlight lang="pascal" inline>round</syntaxhighlight> function. | |
| + | (Note, constant expressions can and will be evaluated ''during'' compile-time, thus the presented techniques do not affect compile-time results.) | ||
| − | <syntaxhighlight lang="pascal"> | + | == invocation == |
| + | <syntaxhighlight lang="pascal" inline>SetRoundMode</syntaxhighlight> resides in the {{Doc|package=RTL|unit=math|text=<syntaxhighlight lang="pascal" inline>math</syntaxhighlight> unit}}. | ||
| + | You need to include the <syntaxhighlight lang="pascal" inline>math</syntaxhighlight> unit in the [[Uses|<syntaxhighlight lang="pascal" inline>uses</syntaxhighlight> clause]]. | ||
| − | The | + | <syntaxhighlight lang="pascal" inline>SetRoundMode</syntaxhighlight> is a unary function. |
| + | The function’s signature reads: | ||
| + | <syntaxhighlight lang="pascal">function setRoundMode(const roundMode: TFPURoundingMode): TFPURoundingMode</syntaxhighlight> | ||
| − | + | The following values are permissible for <syntaxhighlight lang="pascal" inline>roundMode</syntaxhighlight> (cf. {{Doc|package=RTL|unit=system|identifier=tfpuroundingmode|text=<syntaxhighlight lang="pascal" inline>TFPURoundingMode</syntaxhighlight>}}): | |
| − | + | ; <syntaxhighlight lang="pascal" inline>rmNearest</syntaxhighlight> | |
| − | + | : rounds to the nearest ''even'' integer (Banker‘s Rounding: <syntaxhighlight lang="pascal" inline>0.5</syntaxhighlight> rounds down to <syntaxhighlight lang="pascal" inline>0</syntaxhighlight>; <syntaxhighlight lang="pascal" inline>1.5</syntaxhighlight> rounds up to <syntaxhighlight lang="pascal" inline>2</syntaxhighlight>). This is the default. | |
| − | + | ; <syntaxhighlight lang="pascal" inline>rmDown</syntaxhighlight> | |
| + | : generally rounds to the next smaller integer | ||
| + | ; <syntaxhighlight lang="pascal" inline>rmUp</syntaxhighlight> | ||
| + | : generally rounds to the next larger integer | ||
| + | ; <syntaxhighlight lang="pascal" inline>rmTruncate</syntaxhighlight> | ||
| + | : cuts off the decimal places | ||
| − | + | The function will return the previous rounding mode, before it was changed. | |
| + | Thus, it returns the same value as {{Doc|package=RTL|unit=math|identifier=getroundmode|text=<syntaxhighlight lang="pascal" inline>math.getRoundMode</syntaxhighlight>}}. | ||
| − | = | + | {{Warning| |
| + | The setting of the rounding mode applies to all ''internal'' floating point calculations. | ||
| + | In particular, it determines how numbers that cannot be represented exactly as the native floating-point type’s values are to be rounded to the internal representation within the scope of the available bits. | ||
| + | Therefore, the usage of <syntaxhighlight lang="pascal" inline>setRoundMode</syntaxhighlight> for general rounding purposes is not recommended. | ||
| + | }} | ||
| − | * [[Round]] | + | == see also == |
| − | * [[Int]] | + | * [[Round|<syntaxhighlight lang="pascal" inline>round</syntaxhighlight>]] |
| − | * [[Trunc]] | + | * [[Int|<syntaxhighlight lang="pascal" inline>int</syntaxhighlight>]] |
| + | * [[Trunc|<syntaxhighlight lang="pascal" inline>trunc</syntaxhighlight>]] | ||
[[Category:Pascal]] | [[Category:Pascal]] | ||
Latest revision as of 12:12, 21 May 2020
│ Deutsch (de) │ English (en) │
With math.setRoundMode you can set the FPU’s method of rounding.
If no FPU is present, the global variable system.softFloat_rounding_mode will determine the rounding mode for floating-point operations implemented by software.
This also affects the run-time behavior of the round function.
(Note, constant expressions can and will be evaluated during compile-time, thus the presented techniques do not affect compile-time results.)
invocation
SetRoundMode resides in the math unit.
You need to include the math unit in the uses clause.
SetRoundMode is a unary function.
The function’s signature reads:
function setRoundMode(const roundMode: TFPURoundingMode): TFPURoundingMode
The following values are permissible for roundMode (cf. TFPURoundingMode):
rmNearest- rounds to the nearest even integer (Banker‘s Rounding:
0.5rounds down to0;1.5rounds up to2). This is the default. rmDown- generally rounds to the next smaller integer
rmUp- generally rounds to the next larger integer
rmTruncate- cuts off the decimal places
The function will return the previous rounding mode, before it was changed.
Thus, it returns the same value as math.getRoundMode.
Warning:
The setting of the rounding mode applies to all internal floating point calculations.
In particular, it determines how numbers that cannot be represented exactly as the native floating-point type’s values are to be rounded to the internal representation within the scope of the available bits.
Therefore, the usage of setRoundMode for general rounding purposes is not recommended.
