Complex classes like InfiniteDecimal often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use InfiniteDecimal, and based on these observations, apply Extract Interface, too.
| 1 | <?php |
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| 15 | class InfiniteDecimal extends Decimal |
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| 16 | { |
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| 17 | /** |
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| 18 | * Single instance of "Positive Infinite" |
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| 19 | * @var Decimal |
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| 20 | */ |
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| 21 | private static $pInf = null; |
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| 22 | |||
| 23 | /** |
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| 24 | * Single instance of "Negative Infinite" |
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| 25 | * @var Decimal |
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| 26 | */ |
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| 27 | private static $nInf = null; |
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| 28 | |||
| 29 | /** |
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| 30 | * Private constructor |
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| 31 | * @param string $value |
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| 32 | */ |
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| 33 | 2 | private function __construct($value) |
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| 37 | |||
| 38 | /** |
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| 39 | * Private clone method |
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| 40 | */ |
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| 41 | private function __clone() |
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| 45 | |||
| 46 | /** |
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| 47 | * Returns a "Positive Infinite" object |
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| 48 | * @return Decimal |
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| 49 | */ |
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| 50 | 73 | public static function getPositiveInfinite() |
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| 51 | { |
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| 52 | 73 | if (self::$pInf === null) { |
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| 53 | 1 | self::$pInf = new InfiniteDecimal('INF'); |
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| 54 | 1 | } |
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| 55 | |||
| 56 | 73 | return self::$pInf; |
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| 57 | } |
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| 58 | |||
| 59 | /** |
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| 60 | * Returns a "Negative Infinite" object |
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| 61 | * @return Decimal |
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| 62 | */ |
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| 63 | 42 | public static function getNegativeInfinite() |
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| 64 | { |
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| 65 | 42 | if (self::$nInf === null) { |
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| 66 | 1 | self::$nInf = new InfiniteDecimal('-INF'); |
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| 67 | 1 | } |
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| 68 | |||
| 69 | 42 | return self::$nInf; |
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| 70 | } |
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| 71 | |||
| 72 | /** |
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| 73 | * Adds two Decimal objects |
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| 74 | * @param Decimal $b |
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| 75 | * @param integer $scale |
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| 76 | * @return Decimal |
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| 77 | */ |
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| 78 | 2 | public function add(Decimal $b, $scale = null) |
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| 79 | { |
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| 80 | 2 | self::paramsValidation($b, $scale); |
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| 81 | |||
| 82 | 2 | if (!$b->isInfinite()) { |
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| 83 | 1 | return $this; |
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| 84 | 1 | } elseif ($this->hasSameSign($b)) { |
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| 85 | 1 | return $this; |
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| 86 | } else { // elseif ($this->isPositive() && $b->isNegative || $this->isNegative() && $b->isPositive()) { |
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| 87 | 1 | throw new \DomainException("Infinite numbers with opposite signs can't be added."); |
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| 88 | } |
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| 89 | } |
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| 90 | |||
| 91 | /** |
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| 92 | * Subtracts two BigNumber objects |
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| 93 | * @param Decimal $b |
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| 94 | * @param integer $scale |
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| 95 | * @return Decimal |
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| 96 | */ |
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| 97 | 2 | public function sub(Decimal $b, $scale = null) |
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| 98 | { |
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| 99 | 2 | self::paramsValidation($b, $scale); |
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| 100 | |||
| 101 | 2 | if (!$b->isInfinite()) { |
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| 102 | 1 | return $this; |
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| 103 | 1 | } elseif (!$this->hasSameSign($b)) { |
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| 104 | 1 | return $this; |
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| 105 | } else { // elseif () { |
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| 106 | 1 | throw new \DomainException("Infinite numbers with the same sign can't be subtracted."); |
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| 107 | } |
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| 108 | } |
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| 109 | |||
| 110 | /** |
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| 111 | * Multiplies two BigNumber objects |
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| 112 | * @param Decimal $b |
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| 113 | * @param integer $scale |
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| 114 | * @return Decimal |
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| 115 | */ |
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| 116 | 5 | public function mul(Decimal $b, $scale = null) |
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| 117 | { |
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| 118 | 5 | self::paramsValidation($b, $scale); |
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| 119 | |||
| 120 | 5 | if ($b->isZero()) { |
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| 121 | 4 | throw new \DomainException("Zero multiplied by infinite is not allowed."); |
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| 122 | } |
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| 123 | |||
| 124 | 1 | if ($this->hasSameSign($b)) { |
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| 125 | 1 | return self::getPositiveInfinite(); |
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| 126 | } else { // elseif (!$this->hasSameSign($b)) { |
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| 127 | 1 | return self::getNegativeInfinite(); |
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| 128 | } |
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| 129 | } |
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| 130 | |||
| 131 | /** |
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| 132 | * Divides the object by $b . |
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| 133 | * Warning: div with $scale == 0 is not the same as |
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| 134 | * integer division because it rounds the |
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| 135 | * last digit in order to minimize the error. |
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| 136 | * |
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| 137 | * @param Decimal $b |
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| 138 | * @param integer $scale |
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| 139 | * @return Decimal |
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| 140 | */ |
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| 141 | 3 | public function div(Decimal $b, $scale = null) |
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| 155 | |||
| 156 | /** |
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| 157 | * Returns the square root of this object |
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| 158 | * @param integer $scale |
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| 159 | * @return Decimal |
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| 160 | */ |
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| 161 | 2 | public function sqrt($scale = null) |
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| 162 | { |
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| 163 | 2 | if ($this->isNegative()) { |
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| 164 | 1 | throw new \DomainException( |
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| 165 | "Decimal can't handle square roots of negative numbers (it's only for real numbers)." |
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| 166 | 1 | ); |
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| 167 | } |
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| 168 | |||
| 169 | 1 | return $this; |
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| 170 | } |
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| 171 | |||
| 172 | /** |
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| 173 | * Powers this value to $b |
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| 174 | * |
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| 175 | * @param Decimal $b exponent |
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| 176 | * @param integer $scale |
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| 177 | * @return Decimal |
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| 178 | */ |
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| 179 | 7 | public function pow(Decimal $b, $scale = null) |
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| 180 | { |
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| 181 | 7 | if ($b->isPositive()) { |
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| 182 | 3 | if ($this->isPositive()) { |
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| 183 | 1 | return $this; |
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| 184 | } |
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| 185 | |||
| 186 | // if ($this->isNegative()) |
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| 187 | 2 | if ($b->isInfinite()) { |
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| 188 | 1 | throw new \DomainException("Negative infinite elevated to infinite is undefined."); |
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| 189 | } |
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| 190 | |||
| 191 | 1 | if ($b->isInteger()) { |
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| 192 | 1 | if (preg_match('/^[+\-]?[0-9]*[02468](\.0+)?$/', $b->value, $captures) === 1) { |
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| 193 | // $b is an even number |
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| 194 | 1 | return self::$pInf; |
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| 195 | } else { |
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| 196 | // $b is an odd number |
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| 197 | 1 | return $this; // Negative Infinite |
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| 198 | } |
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| 199 | } |
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| 200 | |||
| 201 | throw new NotImplementedException("See issues #21, #22, #23 and #24 on Github."); |
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| 202 | |||
| 203 | 4 | } else if ($b->isNegative()) { |
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| 204 | 2 | return DecimalConstants::Zero(); |
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| 205 | 2 | } else if ($b->isZero()) { |
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| 206 | 2 | throw new \DomainException("Infinite elevated to zero is undefined."); |
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| 207 | } |
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| 208 | } |
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| 209 | |||
| 210 | /** |
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| 211 | * Returns the object's logarithm in base 10 |
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| 212 | * @param integer $scale |
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| 213 | * @return Decimal |
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| 214 | */ |
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| 215 | 2 | public function log10($scale = null) |
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| 216 | { |
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| 217 | 2 | if ($this->isNegative()) { |
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| 218 | 1 | throw new \DomainException( |
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| 219 | "Decimal can't handle logarithms of negative numbers (it's only for real numbers)." |
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| 220 | 1 | ); |
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| 221 | } |
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| 222 | |||
| 223 | 1 | return $this; |
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| 224 | } |
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| 225 | |||
| 226 | /** |
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| 227 | * Equality comparison between this object and $b |
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| 228 | * @param Decimal $b |
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| 229 | * @param integer $scale |
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| 230 | * @return boolean |
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| 231 | */ |
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| 232 | 19 | public function equals(Decimal $b, $scale = null) |
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| 236 | |||
| 237 | /** |
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| 238 | * $this > $b : returns 1 , $this < $b : returns -1 , $this == $b : returns 0 |
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| 239 | * |
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| 240 | * @param Decimal $b |
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| 241 | * @param integer $scale |
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| 242 | * @return integer |
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| 243 | */ |
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| 244 | 2 | public function comp(Decimal $b, $scale = null) |
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| 245 | { |
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| 246 | 2 | self::paramsValidation($b, $scale); |
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| 247 | |||
| 248 | 2 | if ($this === $b) { |
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| 249 | 1 | return 0; |
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| 250 | 2 | } elseif ($this === self::getPositiveInfinite()) { |
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| 251 | 2 | return 1; |
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| 252 | } else { // if ($this === self::getNegativeInfinite()) { |
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| 253 | 2 | return -1; |
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| 254 | } |
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| 255 | } |
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| 256 | |||
| 257 | /** |
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| 258 | * Returns the element's additive inverse. |
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| 259 | * @return Decimal |
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| 260 | */ |
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| 261 | 4 | public function additiveInverse() |
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| 262 | { |
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| 263 | 4 | if ($this === self::getPositiveInfinite()) { |
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| 264 | 3 | return self::$nInf; |
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| 265 | } else { // if ($this === self::getNegativeInfinite()) { |
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| 266 | 4 | return self::$pInf; |
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| 267 | } |
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| 268 | } |
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| 269 | |||
| 270 | /** |
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| 271 | * "Rounds" the Decimal to have at most $scale digits after the point |
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| 272 | * @param integer $scale |
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| 273 | * @return Decimal |
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| 274 | */ |
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| 275 | 1 | public function round($scale = 0) |
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| 279 | |||
| 280 | /** |
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| 281 | * "Ceils" the Decimal to have at most $scale digits after the point |
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| 282 | * @param integer $scale |
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| 283 | * @return Decimal |
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| 284 | */ |
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| 285 | 1 | public function ceil($scale = 0) |
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| 289 | |||
| 290 | /** |
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| 291 | * "Floors" the Decimal to have at most $scale digits after the point |
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| 292 | * @param integer $scale |
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| 293 | * @return Decimal |
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| 294 | */ |
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| 295 | 33 | public function floor($scale = 0) |
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| 299 | |||
| 300 | /** |
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| 301 | * Throws exception because sine is undefined in the infinite. |
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| 302 | * |
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| 303 | * @param integer $scale |
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| 304 | * @return null |
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| 305 | */ |
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| 306 | 2 | public function sin($scale = null) |
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| 307 | { |
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| 308 | 2 | throw new \DomainException(($this === self::$pInf) ? |
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| 309 | 2 | "Sine function hasn't limit in the positive infinite." : |
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| 310 | "Sine function hasn't limit in the negative infinite." |
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| 311 | 2 | ); |
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| 312 | } |
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| 313 | |||
| 314 | /** |
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| 315 | * Throws exception because cosecant is undefined in the infinite. |
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| 316 | * |
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| 317 | * @param integer $scale |
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| 318 | * @return null |
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| 319 | */ |
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| 320 | 2 | public function cosec($scale = null) |
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| 321 | { |
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| 322 | 2 | throw new \DomainException(($this === self::$pInf) ? |
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| 323 | 2 | "Cosecant function hasn't limit in the positive infinite." : |
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| 324 | "Cosecant function hasn't limit in the negative infinite." |
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| 325 | 2 | ); |
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| 326 | } |
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| 327 | |||
| 328 | /** |
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| 329 | * Throws exception because cosine is undefined in the infinite. |
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| 330 | * |
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| 331 | * @param integer $scale |
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| 332 | * @return null |
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| 333 | */ |
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| 334 | 2 | public function cos($scale = null) |
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| 335 | { |
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| 336 | 2 | throw new \DomainException(($this === self::$pInf) ? |
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| 337 | 2 | "Cosine function hasn't limit in the positive infinite." : |
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| 338 | "Cosine function hasn't limit in the negative infinite." |
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| 339 | 2 | ); |
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| 340 | } |
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| 341 | |||
| 342 | /** |
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| 343 | * Throws exception because secant is undefined in the infinite. |
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| 344 | * |
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| 345 | * @param integer $scale |
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| 346 | * @return null |
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| 347 | */ |
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| 348 | 2 | public function sec($scale = null) |
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| 349 | { |
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| 350 | 2 | throw new \DomainException(($this === self::$pInf) ? |
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| 351 | 2 | "Secant function hasn't limit in the positive infinite." : |
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| 352 | "Secant function hasn't limit in the negative infinite." |
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| 353 | 2 | ); |
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| 354 | } |
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| 355 | |||
| 356 | /** |
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| 357 | * Returns exp($this), said in other words: e^$this . |
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| 358 | * |
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| 359 | * @param integer $scale |
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| 360 | * @return Decimal |
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| 361 | */ |
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| 362 | 2 | public function exp($scale = null) |
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| 363 | { |
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| 364 | 2 | if ($this == self::$pInf) { |
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| 365 | 1 | return $this; |
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| 366 | } else { |
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| 367 | 1 | return DecimalConstants::zero(); |
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| 368 | } |
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| 369 | } |
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| 370 | |||
| 371 | 2 | public function tan($scale = null) |
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| 372 | { |
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| 373 | 2 | throw new \DomainException(($this === self::$pInf) ? |
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| 374 | 2 | "Tangent function hasn't limit in the positive infinite." : |
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| 375 | "Tangent function hasn't limit in the negative infinite." |
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| 376 | 2 | ); |
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| 377 | } |
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| 378 | |||
| 379 | 2 | public function cotan($scale = null) |
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| 380 | { |
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| 381 | 2 | throw new \DomainException(($this === self::$pInf) ? |
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| 382 | 2 | "Cotangent function hasn't limit in the positive infinite." : |
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| 383 | "Cotangent function hasn't limit in the negative infinite." |
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| 384 | 2 | ); |
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| 385 | } |
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| 386 | |||
| 387 | /** |
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| 388 | * @param integer $scale Has no effect, exists only for compatibility. |
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| 389 | * @return boolean |
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| 390 | */ |
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| 391 | 36 | public function isZero($scale = null) |
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| 395 | |||
| 396 | /** |
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| 397 | * @return boolean |
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| 398 | */ |
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| 399 | 11 | public function isPositive() |
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| 403 | |||
| 404 | /** |
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| 405 | * @return boolean |
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| 406 | */ |
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| 407 | 12 | public function isNegative() |
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| 411 | |||
| 412 | /** |
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| 413 | * @return boolean |
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| 414 | */ |
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| 415 | public function isInteger() |
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| 419 | |||
| 420 | /** |
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| 421 | * @return boolean |
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| 422 | */ |
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| 423 | 13 | public function isInfinite() |
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| 427 | |||
| 428 | /** |
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| 429 | * Return value as a float |
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| 430 | * |
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| 431 | * @return float |
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| 432 | */ |
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| 433 | 1 | public function asFloat() |
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| 437 | |||
| 438 | /** |
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| 439 | * Return value as a integer |
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| 440 | * |
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| 441 | * @return float |
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| 442 | */ |
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| 443 | 1 | public function asInteger() |
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| 447 | } |
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| 448 |
Overwriting private methods is generally fine as long as you also use private visibility. It might still be preferable for understandability to use a different method name.