Entering and editing code in Elan/div>

## Selecting the programming language(s)

TODO

## Browse code

Watch the video: Browse code

The code shown in the editor has three types:

- Instructions begin with a blue keyword as in:
  `variable namename? set to "Alice"value or expression?0namename? = "Alice"value or expression? # variable definition0var namename? = "Alice"value or expression?;0Dim namename? = "Alice"value or expression? ' variable definition0var namename? = "Alice"value or expression?;0`
- Comments are green and start with a hash # which is optionally followed by text:
  `# A program to investigate the Collatz Conjecturecomment?# A program to investigate the Collatz Conjecturecomment?// A program to investigate the Collatz Conjecturecomment?' A program to investigate the Collatz Conjecturecomment?
  public class Global {
  // A program to investigate the Collatz Conjecturecomment?
  }`
- The first comment in a file (which shows the software version) is automatically created and cannot be edited, deleted or moved.
- new code prompts look like this:
  or, when selected, like this:
  and, on pressing Enter or right click, this menu appears:
  which means that a second press of Enter will choose the (top) print option and a further Enter will supply the procedure call:
  `print(any) Code does not parse as Elan.print(any) Code does not parse as Elan.print(any) Code does not parse as Elan.print(any) Code does not parse as Elan.print(any) Code does not parse as Elan.`
  soliciting values and literals to be printed.
  The reassign variable option inserts a `setsetsetsetset` instruction.
  The initial letters shown in bold indicate the single letter that can be used from the keyboard for that instruction. Other instructions are entered by clicking on them in this menu.

Comments and new code prompts are not instructions. They do not alter the program's behaviour, though they are treated by the editor like instructions.

### To select instructions

To... | Keyboard shortcut | Mouse gesture | Notes
--- | --- | --- | ---
select an arbitrary instruction |  | click on the initial keyword of the instruction or its number |
select the next instruction | ↓ |  | limited to the current block of instructions
select the previous instruction | ↑ |  | limited to the current block of instructions
select the first instruction at the current level of indentation | Home |  |
select the last instruction at the current level of indentation | End |  |
select the outer instruction containing the current one | ← |  |
select the first inner instruction contained by the current one | → |  |
add the next instruction to the current selection | Shift+↓ | Shift, and click on the initial keyword of the instruction or its number | limited to the current block of instructions
add the previous instruction to the current selection | Shift+↑ | Shift, and click on the initial keyword of the instruction or its number | limited to the current block of instructions
toggle outlining on an individual instruction | select the instruction then Ctrl+o | double-click on the initial keyword or instruction number |
toggle outlining for the whole program | Ctrl+O (same as Ctrl+Shift+o) | click the outline button |

## Create new instructions

Watch the video: Create New Instructions

## Edit instructions

### Context menu

When you have selected an instruction by clicking on its keyword (turning its background blue), some immediate actions are available from its context menu which is opened either by clicking the right mouse button on the keyword, or by keying Ctrl+m. The commonest context menu shows these options, any one of which may then be clicked on to do the action:

The context menu shows only those actions which are relevant to that instruction in its context.

The following is a list all possible menu items with key equivalents where applicable:

do | undo | keyboard
--- | --- | ---
insert new code below |  | Enter
insert new code above |  | Shift+Enter
delete |  | Ctrl+Delete or Ctrl+Backspace
move up |  | Ctrl+↑
move down |  | Ctrl+↓
cut for internal use |  | Ctrl+x
copy for internal use |  | Ctrl+c
ghost | unghost |
set breakpoint | clear breakpoint |
clear all breakpoints |  |
copy for external use |  |
make private | make public | Ctrl+p (toggle)

### Select and edit a field

To... | Keyboard shortcut | Mouse gesture | Notes
--- | --- | --- | ---
select any field within an instruction |  | click anywhere on the text, or placeholder, for that field. | Text cursor will be placed at the end of the field
select the first field in a selected instruction | Tab |  |
select the next field in the same instruction | Tab |  | will cycle through the fields and back to the whole instruction.
select the previous field in the same instruction | Shift+Tab |  | will cycle through the fields and back to the whole instruction.
select specific text within a field | Shift+← or → | click and drag across the desired characters |
select all text within a field | Ctrl+a |  |
position text-cursor at the start of a selected field | Home | click anywhere within the selected field |
position text-cursor at the end of a selected field | End | click anywhere within the selected field |
go from the last field to the next instruction | Enter |  |

### Insert a new instruction

If there is already a new code prompt where you want to insert an instruction, refer to the description under Browse code above.

Otherwise, select an instruction adjacent to where you want to add the new one and either:

- key Enter to insert a new code prompt below it, or
- key Shift+Enter to insert a new code prompt above it.

### Delete ...

To delete | Keyboard shortcut | Notes
--- | --- | ---
one or more (adjacent) existing instructions | select the instructions then Ctrl+Delete, Ctrl+Backspace or Ctrl+x | deleting a compound instruction will delete all its contained instructions
a just-created instruction | Backspace | this works only if no fields have been entered or 'child' instructions added
a new code prompt that is not needed | delete the same way as an instruction |
all new code prompts | Click on the Trim button or Alt+t | removes all new code prompts except in places where further instructions are required (for example so as not to leave an empty loop)

### Undo or redo a recent change

The editor retains previous versions of your code in its stack, but only when it has been parsed as valid. The code is saved internally, and also to file if auto-save is selected.

Action | Using the keyboard | Using the mouse
--- | --- | ---
Undo previous changes | Ctrl+z | click on undo button
Redo previous undos | Ctrl+y | click on redo button

### Move instructions up or down within the same block

- Select the instructions, then key Ctrl+↓ or Ctrl+↑.
- Movement is limited to up or down within the current code block.
- To move instructions to a different code block use cut & paste. (It is not currently possible to move instructions using the mouse alone).

### Cut and paste

- To move one or more successive instructions to a new location within the program:
  - Select the instructions to be cut, then key Ctrl+x.
  - Create, or select, a new code prompt where you want to paste in the cut instructions.
  - Key Ctrl+v to paste.
- Note that the pasted instructions must be compatible with their new context, i.e. all of the instructions could have been created there in the first place. If they are incompatible, no paste will take place and you will see a pop-up advisory message. To restore the cut instructions to their original context, use undo.
- To copy or move text between two fields in the program, or between program fields and external text:
- Use the usual select highlight text (Ctrl+a for all of a field) and Ctrl+c to copy or Ctrl+x to cut, and then Ctrl+v to paste it in.

### Ghosting

Instead of being able to 'comment out' code that you wish to retain but not execute, there is a method for 'ghosting' sections of code with much the same effect, while leaving the ghosted code fully formatted.

- Select the single instruction (which may be a compound one, e.g. a while loop, an entire procedure or a test) to be ghosted.
- Ctrl+m or right-click on the instruction keyword, and choose ghost from the context menu.
- The instruction will be displayed in pale colours.
- The ghosted code will then be ignored by the compiler and, for ghosted tests, by the test runner. This means, for example, that you can create two different implementations of the same function and compare them, as long as one of them is ghosted.
- You can ghost code that does not compile, but you should not ghost code that does not parse: the ghosting will work, but you will not then be able to get the program as a whole to parse, and will have to unghost it again to fix it.
- To restore a ghosted instruction, Ctrl+m or right-click on it and choose unghost.
- Ghosted code can be copied, moved or deleted but, to edit ghosted code, you must unghost it first.
- A program containing ghosted code can be saved.
- Code containing ghosted instructions can be ghosted at a higher level, and remains ghosted when the higher level is unghosted.

## Debugging programs

Watch the video: Debugging programs

You can debug a running program with or without having set breakpoints.

### Run in debug mode, pause, and step

To... | Keyboard shortcut | Mouse gesture | Notes
--- | --- | --- | ---
debug a program, or resume debugging a paused program | Ctrl+g | Click on 'debug' button | disabled if there are any parse or compile issues.
pause a program that is running | Ctrl+u | Click on 'pause' button | enabled only when program is being debugged
step to the next instruction in a paused program | Ctrl+p | Click on 'step' button | enabled only then program is paused

### Browsing named values

Whenever the program is paused, all named values (variables, parameters and constant values) that are currently in scope have their values automatically listed in the Info pane. This list may be browsed as follows:

To... | Keyboard shortcut | Mouse gesture
--- | --- | ---
navigate to a specific line in the list when paused | Tab, Shift+Tab | Click on the line
expand/collapse a specific name within the list | Enter | Click on the + or - at the start of the line

### Using breakpoints

Before clicking on debug you can set breakpoints at one or more instructions where you want execution to pause. A red flash symbol appears at every instruction that has a breakpoint defined..

When run using debug the program will automatically pause at every breakpoint, and the in-scope named values will be listed in the Info pane.

To... | Keyboard shortcut | Mouse gesture
--- | --- | ---
set a breakpoint on a selected instruction | Ctrl+m on a selected instruction keyword then select set breakpoint | right-click for context menu, then select set breakpoint
clear existing breakpoints | Ctrl+m on a selected instruction keyword, then select clear breakpoint or clear all breakpoints | right-click for context menu, then select clear breakpoint or clear all breakpoints

## Apple macOS specific

Where a keyboard shortcut is shown with the Ctrl control key, users of Apple's macOS should use the ⌘ Command key instead.

## Colour scheme for CVD

There are two ways in which to change the colour scheme for users with CVD:

- Button file has menu option preferences which offers an alternative colour scheme via a small dialogue. Whether or not you tick the CVD option, clicking confirm automatically tries to reload the web page, so you will receive a warning (which you can cancel) if you have unsaved code. You can also just press Escape to remove the dialogue.
- The URL provided to a pupil may include a CVD scheme, as described above in Launch the IDE.

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