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1 package fj.function;
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2
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3 import fj.F;
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4 import fj.F2;
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5 import static fj.Function.curry;
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6
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7 import fj.Monoid;
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8 import fj.data.List;
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9 import fj.data.Option;
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10 import static fj.data.Option.some;
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11 import static fj.data.Option.none;
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12 import static fj.Semigroup.intAdditionSemigroup;
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13 import static fj.Semigroup.intMultiplicationSemigroup;
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14
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15 import static java.lang.Math.abs;
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16
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17 /**
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18 * Curried functions over Integers.
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19 *
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20 * @version %build.number%
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21 */
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22 public final class Integers {
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23 private Integers() {
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24 throw new UnsupportedOperationException();
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25 }
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26
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27 /**
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28 * Curried Integer addition.
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29 */
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30 public static final F<Integer, F<Integer, Integer>> add = intAdditionSemigroup.sum();
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31
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32 /**
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33 * Curried Integer multiplication.
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34 */
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35 public static final F<Integer, F<Integer, Integer>> multiply = intMultiplicationSemigroup.sum();
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36
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37 /**
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38 * Curried Integer subtraction.
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39 */
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40 public static final F<Integer, F<Integer, Integer>> subtract = curry(new F2<Integer, Integer, Integer>() {
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41 public Integer f(final Integer x, final Integer y) {
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42 return x - y;
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43 }
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44 });
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45
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46 /**
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47 * Negation.
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48 */
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49 public static final F<Integer, Integer> negate = new F<Integer, Integer>() {
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50 public Integer f(final Integer x) {
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51 return x * -1;
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52 }
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53 };
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54
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55 /**
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56 * Absolute value.
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57 */
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58 public static final F<Integer, Integer> abs = new F<Integer, Integer>() {
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59 public Integer f(final Integer x) {
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60 return abs(x);
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61 }
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62 };
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63
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64 /**
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65 * Remainder.
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66 */
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67 public static final F<Integer, F<Integer, Integer>> remainder = curry(new F2<Integer, Integer, Integer>() {
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68 public Integer f(final Integer a, final Integer b) {
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69 return a % b;
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70 }
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71 });
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72
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73 /**
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74 * Power.
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75 */
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76 public static final F<Integer, F<Integer, Integer>> power = curry(new F2<Integer, Integer, Integer>() {
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77 public Integer f(final Integer a, final Integer b) {
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78 return (int) StrictMath.pow(a, b);
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79 }
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80 });
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81
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82 /**
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83 * Evenness.
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84 */
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85 public static final F<Integer, Boolean> even = new F<Integer, Boolean>() {
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86 public Boolean f(final Integer i) {
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87 return i % 2 == 0;
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88 }
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89 };
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90
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91 /**
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92 * Sums a list of integers.
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93 *
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94 * @param ints A list of integers to sum.
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95 * @return The sum of the integers in the list.
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96 */
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97 public static int sum(final List<Integer> ints) {
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98 return Monoid.intAdditionMonoid.sumLeft(ints);
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99 }
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100
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101 /**
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102 * Returns the product of a list of integers.
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103 *
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104 * @param ints A list of integers to multiply together.
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105 * @return The product of the integers in the list.
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106 */
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107 public static int product(final List<Integer> ints) {
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108 return Monoid.intMultiplicationMonoid.sumLeft(ints);
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109 }
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110
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111 /**
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112 * A function that converts strings to integers.
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113 *
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114 * @return A function that converts strings to integers.
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115 */
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116 public static F<String, Option<Integer>> fromString() {
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117 return new F<String, Option<Integer>>() {
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118 public Option<Integer> f(final String s) {
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119 try { return some(Integer.valueOf(s)); }
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120 catch (final NumberFormatException ignored) {
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121 return none();
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122 }
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123 }
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124 };
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125 }
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126
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127 /**
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128 * A function that returns true if the given integer is greater than zero.
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129 */
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130 public static final F<Integer, Boolean> gtZero = new F<Integer, Boolean>() {
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131 public Boolean f(final Integer i) {
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132 return i > 0;
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133 }
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134 };
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135
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136 /**
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137 * A function that returns true if the given integer is greater than or equal to zero.
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138 */
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139 public static final F<Integer, Boolean> gteZero = new F<Integer, Boolean>() {
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140 public Boolean f(final Integer i) {
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141 return i >= 0;
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142 }
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143 };
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144
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145 /**
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146 * A function that returns true if the given integer is less than zero.
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147 */
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148 public static final F<Integer, Boolean> ltZero = new F<Integer, Boolean>() {
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149 public Boolean f(final Integer i) {
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150 return i < 0;
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151 }
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152 };
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153
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154 /**
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155 * A function that returns true if the given integer is less than or equal to zero.
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156 */
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157 public static final F<Integer, Boolean> lteZero = new F<Integer, Boolean>() {
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158 public Boolean f(final Integer i) {
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159 return i <= 0;
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160 }
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161 };
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162 }
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