[381f18]: doc / html / logic_programming / pattern_matching / tuple_patterns.html Maximize Restore History

tuple_patterns.html    176 lines (162 with data), 7.8 kB

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174``` ``` Tuple Patterns

Hosted by:

Tuple Patterns

Tuple patterns only match tuples. They are written as simply a comma separated list of patterns within parenthesis:

(1, \$x, "buckle my shoe")

You can also write a rest pattern variable at the end using an asterisk (*):

(\$a, fie, \$b, *\$c)

This will match the rest of the items in the data value that the tuple pattern is matched to. Note that the rest pattern variable is always bound to a tuple.

Examples:

• matching (1, \$x, "buckle my shoe") to (1, 2, "buckle my shoe") matches, binding \$x to 2.
• matching (1, \$x, "buckle my shoe") to (1, 2, "buckle my belt") does not match because the third pattern within the tuple pattern fails to match the third value in the matched tuple.
• matching (\$a, fie, \$b, *\$c) to (fee, fie, foe, fum) matches, binding \$a to fee, \$b to foe and \$c to (fum).
• matching (\$a, fie, \$b, *\$c) to (fee, fie, foe) matches, binding \$a to fee, \$b to foe and \$c to ().
• matching (\$a, fie, \$b, *\$c) to (fee, fie) does not match because the data value has to have a length of at least three.

Hint

You can use (*\$foo) to only match a tuple. It will bind \$foo to the entire tuple, but will fail to match any other data type.

More:

Literal Patterns

Explanation of literal patterns.

Pattern Variables

Explanation of pattern variables.

Tuple Patterns

Explanation of tuple patterns.

Matching Two Patterns

Explanation of matching two patterns together, vs matching a pattern to data.