IDE controls & keyboard shortcuts

## Navigate around the IDE

Watch the video: Navigate around the IDE

Always use Elan with the browser in 'full screen mode' – it makes more space available and is safer.

To change the text size, hold down the Ctrl key and use the mouse scroll wheel, or change the magnification via the browser's zoom menu.

If an area has a blue tinted background, it does not have browser 'focus' and will not respond to keyboard input. Use keyboard shortcuts or mouse or touch gestures to change the focus (which is indicated by a white background):

To focus on... | Keyboard shortcut | Mouse gesture | Notes
--- | --- | --- | ---
code editor | Ctrl-e | Click on background within editor | See also Browse code
display | Ctrl-d | Click on the 'display' tab | To clear the Display pane, use the clear button shown within it
info | Ctrl-i | Click on the 'info' tab | To clear the Info pane, use the clear button shown within it
help | Ctrl-h | Click on the 'help' tab |
worksheet | Ctrl-k | Click on the 'worksheet' tab | (Ctrl-w is interpreted by the browser as 'leave web site')
a button | Ctrl-b | Click on the button | Ctrl-b puts focus on the first active button Use Tab or Shift-Tab to navigate to another active button

## Load, run, and save programs

Watch the video: Load, run, and save programs

### Loading and saving

To access the demo or file menus via the keyboard:

- If the menus are disabled, you need to stop the program currently running
- press Ctrl-b then Tab to the menu (if needed)
- press Enter to open the menu
- press ↓ or ↑ to select the required menu item
- press Enter to action the selected item

Intention | Menu action | Notes
--- | --- | ---
use a demo program | demo then select desired program |
load a program file | file > load | if the editor contains unsaved code, you will be warned
append a file to the current code in the editor | file > append | external code is always appended to the end of the current code, but may then be moved
import a file into the current code in the editor | file > import | see Importing code
save a program file | file > auto save | any subsequent edits will be saved to the file (whenever the code parses)
cancel auto-saving | file > cancel auto save | this action appears only after setting up auto save
save a program manually | file > manual save | saves the code to file but does not automatically save subsequent changes
create a standalone Html page incorporating your program | file > save as standalone | the saved .html file contains the compiled program, and will run automatically when opened

#### Importing code

Existing Elan code may be imported into a new program via File > Import. This can facilitate re-use of code and the development of libraries. Importing differs from appending (see table above) in the following ways:

- Imported code is shown in summarised form, with each global-level instruction rendered as a single line, like you would see in the Outline view, and prefixed by the keyword import (except for imported comments which are unchanged).
- Imported code is always placed at the top of the file.

#### Notes

- When you import a file, all instructions within the file are imported at once, include. However you may then immediately delete any parts that you do not need, provided that no other code depends upon them. If you do accidentally delete any imported instruction on which others depend you will get a compile error - but you can restore the deleted items with Undo.
- It is not possible to edit imported code, nor to examine code that is not visible in the summary view. If you need that capability, use File > Append instead (see table above).
- When you import code you capture the state of that code at the time of the import. Subsequent edits to the original file will not update the imports, though you may update them by deleting the imported instructions, and importing the code afresh.

### Running and stopping programs

To... | Keyboard shortcut | Mouse gesture | Notes
--- | --- | --- | ---
run a program | Ctrl-r | Click on 'run' button | disabled if there are any parse or compile issues.
stop a program that is running | Ctrl-s | Click on 'stop' button | Enabled only when the program is running

If your program is doing intensive processing between interactions with you through the IDE, then clicking on the 'stop' button may not have an immediate effect. This is an unavoidable side effect within the browser, but you will be returned to editing after a short period. Avoid repeatedly clicking 'stop' as that might cause the browser tab to be closed.

See also Debugging programs

## Browse code

Watch the video: Browse code

The code shown in the editor has three types:

- Instructions begin with a blue keyword as in: let name be "Alice"
- Comments start with a hash # which is optionally followed by text: # A program to investigate the Collatz Conjecture The first comment in a file (which shows the Elan version) is automatically created and cannot be edited, deleted or moved.
- 'new code' prompts look like this: new code, or like this when selected: new code
  call each for if let print repeat set throw try variable while #
  though the specific keywords offered will depend upon the context.

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 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
--- | --- | ---
ghost | unghost |
copy |  | Ctrl-c
cut |  | Ctrl-x
delete |  | Ctrl-Delete or Ctrl-Backspace
insert new code below |  | Enter
insert new code above |  | Shift-Enter
move up |  | Ctrl-↑
move down |  | Ctrl-↓
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 then:

- select the 'new code' prompt (as you would select an instruction)
- type the first letter of the desired instruction, and more if several valid instructions begins the same way, until an instruction template is inserted, with the focus placed on its first field.

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, Elan provides 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, or an entire procedure) 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 cannot be moved, deleted or edited without unghosting 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 let 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 Mac specific

Where a keyboard shortcut is shown with the Ctrl control key, on an Apple Mac you should use the macOS ⌘ Command key instead.

## Change colour scheme for CVD

Button File has menu option Preferences which offers a slightly modified colour scheme for users with CVD. Note that switching colour schemes automatically re-loads the web page – so you will receive a warning if you have unsaved code.

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