Add filter, map, reduce to Array.
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Stephen Chung
@@ -30,22 +30,25 @@ Built-in Functions
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The following methods (mostly defined in the [`BasicArrayPackage`][packages] but excluded if using a [raw `Engine`]) operate on arrays:
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| Function | Parameter(s) | Description |
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| ------------------------- | -------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------- |
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| `push` | element to insert | inserts an element at the end |
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| `append` | array to append | concatenates the second array to the end of the first |
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| `+=` operator | 1) array<br/>2) element to insert (not another array) | inserts an element at the end |
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| `+=` operator | 1) array<br/>2) array to append | concatenates the second array to the end of the first |
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| `+` operator | 1) first array<br/>2) second array | concatenates the first array with the second |
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| `insert` | 1) element to insert<br/>2) position (beginning if <= 0, end if >= length) | inserts an element at a certain index |
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| `pop` | _none_ | removes the last element and returns it ([`()`] if empty) |
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| `shift` | _none_ | removes the first element and returns it ([`()`] if empty) |
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| `remove` | index | removes an element at a particular index and returns it, or returns [`()`] if the index is not valid |
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| `reverse` | _none_ | reverses the array |
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| `len` method and property | _none_ | returns the number of elements |
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| `pad` | 1) target length<br/>2) element to pad | pads the array with an element to at least a specified length |
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| `clear` | _none_ | empties the array |
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| `truncate` | target length | cuts off the array at exactly a specified length (discarding all subsequent elements) |
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| Function | Parameter(s) | Description |
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| ------------------------- | ------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `push` | element to insert | inserts an element at the end |
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| `append` | array to append | concatenates the second array to the end of the first |
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| `+=` operator | 1) array<br/>2) element to insert (not another array) | inserts an element at the end |
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| `+=` operator | 1) array<br/>2) array to append | concatenates the second array to the end of the first |
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| `+` operator | 1) first array<br/>2) second array | concatenates the first array with the second |
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| `insert` | 1) element to insert<br/>2) position (beginning if <= 0, end if >= length) | inserts an element at a certain index |
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| `pop` | _none_ | removes the last element and returns it ([`()`] if empty) |
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| `shift` | _none_ | removes the first element and returns it ([`()`] if empty) |
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| `remove` | index | removes an element at a particular index and returns it, or returns [`()`] if the index is not valid |
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| `reverse` | _none_ | reverses the array |
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| `len` method and property | _none_ | returns the number of elements |
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| `pad` | 1) target length<br/>2) element to pad | pads the array with an element to at least a specified length |
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| `clear` | _none_ | empties the array |
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| `truncate` | target length | cuts off the array at exactly a specified length (discarding all subsequent elements) |
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| `filter` | 1) array<br/>2) [function pointer] to predicate (can be a [closure]) | constructs a new array with all items that returns `true` when called with the predicate function:<br/>1st parameter: array item,<br/>2nd parameter: offset index (optional) |
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| `map` | 1) array<br/>2) [function pointer] to conversion function (can be a [closure]) | constructs a new array with all items mapped to the result of applying the conversion function:<br/>1st parameter: array item,<br/>2nd parameter: offset index (optional) |
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| `reduce` | 1) array<br/>2) [function pointer] to accumulator function (can be a [closure]) | constructs a new array with all items accumulated by the accumulator function:<br/>1st parameter: accumulated value ([`()`] initially),<br/>2nd parameter: array item,<br/>3rd parameter: offset index (optional) |
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Use Custom Types With Arrays
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@@ -63,12 +66,12 @@ Examples
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--------
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```rust
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let y = [2, 3]; // array literal with 2 elements
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let y = [2, 3]; // array literal with 2 elements
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let y = [2, 3,]; // trailing comma is OK
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let y = [2, 3,]; // trailing comma is OK
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y.insert(0, 1); // insert element at the beginning
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y.insert(999, 4); // insert element at the end
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y.insert(0, 1); // insert element at the beginning
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y.insert(999, 4); // insert element at the end
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y.len == 4;
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@@ -77,21 +80,21 @@ y[1] == 2;
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y[2] == 3;
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y[3] == 4;
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(1 in y) == true; // use 'in' to test if an item exists in the array
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(42 in y) == false; // 'in' uses the '==' operator (which users can override)
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// to check if the target item exists in the array
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(1 in y) == true; // use 'in' to test if an item exists in the array
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(42 in y) == false; // 'in' uses the '==' operator (which users can override)
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// to check if the target item exists in the array
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y[1] = 42; // array elements can be reassigned
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y[1] = 42; // array elements can be reassigned
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(42 in y) == true;
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y.remove(2) == 3; // remove element
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y.remove(2) == 3; // remove element
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y.len == 3;
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y[2] == 4; // elements after the removed element are shifted
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y[2] == 4; // elements after the removed element are shifted
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ts.list = y; // arrays can be assigned completely (by value copy)
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ts.list = y; // arrays can be assigned completely (by value copy)
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let foo = ts.list[1];
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foo == 42;
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@@ -99,7 +102,7 @@ let foo = [1, 2, 3][0];
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foo == 1;
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fn abc() {
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[42, 43, 44] // a function returning an array
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[42, 43, 44] // a function returning an array
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}
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let foo = abc()[0];
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@@ -108,32 +111,51 @@ foo == 42;
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let foo = y[0];
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foo == 1;
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y.push(4); // 4 elements
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y += 5; // 5 elements
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y.push(4); // 4 elements
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y += 5; // 5 elements
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y.len == 5;
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let first = y.shift(); // remove the first element, 4 elements remaining
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let first = y.shift(); // remove the first element, 4 elements remaining
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first == 1;
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let last = y.pop(); // remove the last element, 3 elements remaining
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let last = y.pop(); // remove the last element, 3 elements remaining
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last == 5;
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y.len == 3;
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for item in y { // arrays can be iterated with a 'for' statement
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for item in y { // arrays can be iterated with a 'for' statement
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print(item);
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}
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y.pad(10, "hello"); // pad the array up to 10 elements
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y.pad(10, "hello"); // pad the array up to 10 elements
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y.len == 10;
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y.truncate(5); // truncate the array to 5 elements
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y.truncate(5); // truncate the array to 5 elements
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y.len == 5;
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y.clear(); // empty the array
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y.clear(); // empty the array
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y.len == 0;
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let a = [42, 123, 99];
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a.map(|v| v + 1); // [43, 124, 100]
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a.map(|v, i| v + i); // [42, 124, 101]
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a.filter(|v| v > 50); // [123, 99]
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a.filter(|v, i| i == 1); // [123]
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a.reduce(|sum, v| {
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// Detect the initial value of '()'
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if sum.type_of() == "()" { v } else { sum + v }
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) == 264;
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a.reduce(|sum, v, i| {
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if i == 0 { v } else { sum + v }
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) == 264;
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```
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