Go/Arrays - Revision history

Admin: /* Initialization */

2018-12-14T18:09:55Z

Initialization

← Older revision		Revision as of 18:09, 14 December 2018
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	==Initialization==		==Initialization==

	~~To initialize~~ an array~~, use~~ the ~~familiar square bracket notation~~.		The most important thing to understand about arrays is that they are different from slices.

			If we create the variable like this:

			<pre>
			var keys [3]int
			</pre>

			it is an array type. That's because we've specified the precise capacity that keys should have.

			But if we create the variable like this:

	<pre>		<pre>
	var keys []int		var keys []int
	~~for k := 0; k < 10; k++ {~~
	~~keys = append(keys, k)~~
	}
	</pre>		</pre>

	In ~~this way~~, we ~~can think~~ of Go's ~~built-in~~ array ~~data structure as being a bit like Java's ArrayList data structure~~, ~~in that it provides high-level methods that don't require the user to re-allocate space every time.~~		it is a slice type. That's because we did not specify the capacity.

			In both cases, we have not actually initialized the value of either variable. Here's how we create an array:

			<pre>
			keys := [3]int{10,20,30}
			</pre>

	==Array size is a part of the type==		==Array size is a part of the type==

Admin: /* Array slices */

2018-12-13T22:51:44Z

Array slices

← Older revision		Revision as of 22:51, 13 December 2018
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	See [[Go/Slices]]		See [[Go/Slices]]

			==Comparison==

			Let's cover how to compare arrays.

			Array values are comparable if values of the array element type are comparable.

			Two array values are equal if their corresponding elements are equal.

			However, note that you cannot compare slices: https://play.golang.org/p/Kk8osjPm8n

			Likewise: https://play.golang.org/p/kCVoPekPudc

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Admin: /* Arrays in Go */

2018-12-13T21:34:01Z

Arrays in Go

← Older revision		Revision as of 21:34, 13 December 2018
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	Go blog post: arrays, slices, and strings: https://blog.golang.org/slices		Go blog post: arrays, slices, and strings: https://blog.golang.org/slices

	=~~Arrays in Go~~=		=Basics=

	~~"Arrays are not often seen in Go programs because the size of~~ an array ~~is part of its type~~, ~~which limits its expressive power~~."		==Initialization==

			To initialize an array, use the familiar square bracket notation.

			<pre>
			var keys []int
			for k := 0; k < 10; k++ {
			keys = append(keys, k)
			}
			</pre>

	~~The most common use of arrays are to store slices~~, ~~which~~ we ~~will see~~ in a ~~moment~~.		In this way, we can think of Go's built-in array data structure as being a bit like Java's ArrayList data structure, in that it provides high-level methods that don't require the user to re-allocate space every time.

	==Array size is a part of the type==		==Array size is a part of the type==

	An important characteristic of arrays is that their size is a part of their type.		An important characteristic of arrays is that their size is a part of their type.

			"Arrays are not often seen in Go programs because the size of an array is part of its type, which limits its expressive power."

	The two variables defined here are of two distinct types:		The two variables defined here are of two distinct types:

Admin: /* Array slices */

2018-12-13T02:27:37Z

Array slices

@@ Line 22: / Line 22: @@
 ==Array slices==
-The bracket notation with colons can be used to refer to a slice of an array. For example:
+See [[Go/Slices]]
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Admin: /* Slice Tricks */

2018-12-13T00:09:23Z

Slice Tricks

← Older revision		Revision as of 00:09, 13 December 2018
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	Communty Go wiki: https://github.com/golang/go/wiki/SliceTricks		Communty Go wiki: https://github.com/golang/go/wiki/SliceTricks

			Go 101 book: https://github.com/go101/go101/wiki

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Admin: /* Array Slice Insertion */

2018-12-13T00:08:36Z

Array Slice Insertion

← Older revision		Revision as of 00:08, 13 December 2018
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	This was an exercise in futility. See [[Go/Arrays/Array Slice Insertion]]		This was an exercise in futility. See [[Go/Arrays/Array Slice Insertion]]

			===Slice Tricks===

			Communty Go wiki: https://github.com/golang/go/wiki/SliceTricks

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Admin: /* Built-In Method: Slice append */

2018-12-13T00:07:38Z

Built-In Method: Slice append

← Older revision		Revision as of 00:07, 13 December 2018
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	This was an exercise in futility. See [[Go/Arrays/Array Slice Insertion]]		This was an exercise in futility. See [[Go/Arrays/Array Slice Insertion]]

	~~==Built-In Method: Slice append==~~

	~~The built-in append() method of slices does exactly what the examples covered in this [https://blog.golang.org/slices rather poorly written blog post] do, namely, insert an item into a slice.~~

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Admin: /* Array Slice Insertion */

2018-12-13T00:07:29Z

Array Slice Insertion

← Older revision		Revision as of 00:07, 13 December 2018
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	This was an exercise in futility. See [[Go/Arrays/Array Slice Insertion]]		This was an exercise in futility. See [[Go/Arrays/Array Slice Insertion]]


	~~The Go blog (this post: https://blog.golang.org/slices) gets lost on a (rather stupid and uninformative) topic, which is, array slices.~~

	~~To insert an element into a slice of an array, we can do the following (NOTE: This is NOT the same as inserting an element into an array):~~

	* Extend the slice window by 1
	* Shift the upper part of the slice's underlying array data up by 1, using the copy function
	** Copying FROM the variable slice, starting at index and running to the end
	** Copying TO the variable slice, starting at index + 1 and running to the end
	* Return the new slice

	~~This operation WILL NOT affect the underlying data.~~

	~~Here is the Insert function, plus a main method that calls it:~~

	~~<pre>~~
	~~// Insert inserts the value into the slice at the specified index,~~
	~~// which must be in range.~~
	~~// The slice must have room for the new element.~~
	~~func Insert(slice []int, index, value int) []int {~~

	~~// Grow the slice by one element.~~
	~~slice = slice[0 : len(slice)+1]~~

	~~// Use copy to move the upper part of the slice out of the way and open a hole.~~
	~~copy(slice[index+1:], slice[index:])~~

	~~// Store the new value.~~
	~~slice[index] = value~~

	~~// Return the result.~~
	~~return slice~~
	}
	~~</pre>~~

	Aside from the stupidity of the example (not making clear why you would want to insert something into a slice of an array but not the array itself; not making clear the underlying data or the memory/reference model in Go).

	~~Basically this whole blog post is a hot mess.~~

	~~The confusion here is, the text seems to contradict the behavior of this function.~~

	* The text describing this example insists we are passing a copy of the slice, but that copy should refer to the same data underneath.
	* However, when we expand the length of the slice, and shift everything over, and insert a value, this doesn't affect the data underneath.

	~~The answer: we aren't creating a slice by saying <code>slice = orig[5:10]</code>, we are creating a slice by saying <code>slice = make([]int, 4, 8)</code> and then <code>copy(slice,orig)</code>.~~

	~~When we call make, we're basically allocating an underlying array for a slice.~~

	~~[https://stackoverflow.com/questions/9320862/why-would-i-make-or-new Related question on Stack Overflow]~~

	==Built-In Method: Slice append==		==Built-In Method: Slice append==

Admin: /* Array Slice Insertion */

2018-12-13T00:06:59Z

Array Slice Insertion

← Older revision		Revision as of 00:06, 13 December 2018
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	===Array Slice Insertion===		===Array Slice Insertion===

	The Go blog gets lost on a (rather stupid and uninformative) topic, which is, array slices.		This was an exercise in futility. See [[Go/Arrays/Array Slice Insertion]]


			The Go blog (this post: https://blog.golang.org/slices) gets lost on a (rather stupid and uninformative) topic, which is, array slices.

	To insert an element into a slice of an array, we can do the following (NOTE: This is NOT the same as inserting an element into an array):		To insert an element into a slice of an array, we can do the following (NOTE: This is NOT the same as inserting an element into an array):

Admin: /* Array Slice Insertion */

2018-12-13T00:05:09Z

Array Slice Insertion

← Older revision		Revision as of 00:05, 13 December 2018
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	[https://stackoverflow.com/questions/9320862/why-would-i-make-or-new Related question on Stack Overflow]		[https://stackoverflow.com/questions/9320862/why-would-i-make-or-new Related question on Stack Overflow]

			==Built-In Method: Slice append==

			The built-in append() method of slices does exactly what the examples covered in this [https://blog.golang.org/slices rather poorly written blog post] do, namely, insert an item into a slice.

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