Arrays 101: All you need to know about them!

[JohnOne]

Let's move onto 

Rule #2: You must specify the no. of elements & dimensions if you are gonna declare an array without any data

You must also declare an array's  "no. of elements & dimensions" even if you are assigning it data.

Suggestion "If you declare an array that is not created by a function, you must specify its "no. of elements & dimensions" size."

Edited October 19, 2015 by JohnOne

[TheDcoder]

@JohnOne Appreciated!

[Melba23]

JohnOne,

You must also declare an array's  "no. of elements & dimensions" even if you are assigning it data

Not quite true - you must declare the number of dimensions, but not necessarily their size if you declare the data:

#include <Array.au3>

Global $aArray[][] = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

_ArrayDisplay($aArray, "", Default, 8)

Obviously if the data does not fill the entire dimension you need to define the full size explicitly.

M23

[JohnOne]

I thought that would be a map.

[Melba23]

JohnOne,

No, you only create a Map (using the Beta) when you declare with empty [ ] and no data:

Both Arrays and Maps use similar syntax, so care is required to ensure the variable is of the correct datatype - this is determined by the first declaration line for the variable:

Using empty [ ] declares a Map:

  Local $vVar[] ; A Map

Filling the [ ] with a dimension size declares an Array:

 Local $vVar[3] ; An Array

Assigning element values when declaring makes the variable an Array - these three lines are functionally equivalent:

  Local $vVar[3] = [1, 2, 3] ; An Array
  Local $vVar[] = [1, 2, 3] ; An Array
  Local $vVar = [1, 2, 3] ; An Array

There has been some internal debate as to whether there should be a different syntax for Maps (such as { }) but there is a lot of work that needs to be done to get them working correctly before we ever get to that level of detail.

M23

[TheDcoder]

I altered Rule 2...

About Maps, Aren't they just arrays which which use strings instead of integers to access the elements?

Local $aArray[1] = ["Data"]
Local $mMap[]

$mMap['data'] = "Data"

Edited October 20, 2015 by TheDcoder
Syntax correction

[Melba23]

TheDcoder,

No, they are much more versatile then that - take a look here.

M23

Edited October 19, 2015 by Melba23
Added direct link

[TheDcoder]

Please post the post #

My Firefox stops at the bottom of the page

[JohnOne]

It's a thread discussion not a single post.

[iamtheky]

If someone smrt could explain the efficiencies of  "map -vs- scripting dictionary"  that would help.  As best I can determine its decent mimicry.

[guinness]

Local $mMap[] = ["Data" => "Data"]

When did AutoIt become PHP?

[JohnOne]

If someone smrt could explain the efficiencies of  "map -vs- scripting dictionary"  that would help.  As best I can determine its decent mimicry.

I cannot fulfill your criteria but one difference I can see is that you cannot store and use a function in a scripting dictionary.

[TheDcoder]

@guinness The moment when I learned PHP

[TheDcoder]

@TheDcoder, maybe you could answer this question...why does the index value start from zero and not one?

Sorry for very late reply, I didn't notice that question earlier . I have multiple hypotheses on this question.

#1 They way the Windows Memory Manager (or Memory Allocator? Something like that ) parses a variable (with a pointer thing?) has a advantage with using 0 as the base index for arrays... Something like there is no way around to set its base to 1 without using index - 1 method to access the elements

#2 Some intelligent group of early programmers decided that everything should start with 0... viz. the of birth 0 based array

#3 Something to do with hardware.. Advantage for using 0 again...

#4 Maybe the least likely situation would be Binary, binary is all 0's and 1's... so why waste the 00110000 (1 byte) key of zero... (one's binary key is 00110001)

 

TD

[guinness]

Maybe Google it, you were close I guess.

Edited December 27, 2015 by guinness

[TheDcoder]

@guinness I tried, I found very detailed and complicated HTML documents about it... A deeper search again this time revealed this:

Zero-based indexing actually simplifies array-related math for the programmer, and simpler math leads to fewer bugs.

- Anders Kaseorg, Quora

Edited December 27, 2015 by TheDcoder
THAT LINK INSERTION BUG IN IPS'S MODIFIED WYSIWYG CK-EDITOR

[guinness]

Yeah and also look at arrays and pointer arithmetic.

[TheDcoder]

@guinness Ok... I am going to start learning C++ soon after I complete my current project, Maybe then I will be able to understand the pointer stuff

[TheDcoder]

Updated the first post

[TheDcoder]

I just updated the 101:

Added FAQ #5 and Looping through loops!

 

Enjoy learning! TD