You've already seen that Alice uses menus for a large number of things. The most important menus are the ones that contain the commands of Alice. We're going to look at these in this chapter. We'll be using the squares program in our examples again, so you should load the program in when you start Alice up.
Every Alice command can be found on at least one command menu, and some commands appear on more than one. Every command can be executed from a menu in addition to any other ways of issuing the command.
For example, you can SAVE a program by pressing [ALT-S] or by choosing the Save selection from the Files Menu. Which way is better? They're both the same. If you remember that [ALT-S] means Save, it's the fastest way to save your program. If you forget what you have to push to save a program, you can always call up the Files Menu and choose Save from that.
A natural question: what happens if you forget what you have to push to call up the Files Menu? That's answered in the next section.
Press [F7]. This produces the Master Menu. If you remember this key, you'll be able to get at all the other menus of Alice. (In fact, if you work at it, you can do 90% of all your programming with just [F10], [F7], and the arrow keys, selecting everything you can from menus. Of course, this wouldn't be very fast...)
Looking at the Master Menu, you see that there are really quite a number of menus available.
Screen Shot mastmenu not available
Some of these you already know about. For example, choose the File Operations selection. You should recognize this as the Files Menu. You get exactly the same thing if you press [F8] -- try it.
Call up the Master Menu again and this time choose the What can I type here? selection. You'll get an Input Menu, the same thing that you'd get if you chose
What can I type here?
from the Help Menu or if you pressed [ALT-T]. Similarly, if you choose
Information about Pascal
you get the same thing that you get if you choose Information about Pascal from the Help Menu or if you pressed [ALT-P]. Again, prove this to yourself by trying it.
The other entry on the Master Menu that you already know about is
Possible Symbols
This gives you the same kind of symbol list that you get by pressing [END].
When you get rid of the selections we've already talked about, the Master Menu reduces to this.
Insertions Deletions Change Structures Move Cursor Misc Running the Program Special Changes
In the rest of this chapter, we'll talk about these different menus.
You get the Deletion Menu by selecting the Deletions entry from the Master Menu. You can also get the menu by pressing [F3]. Press [F3] now to have a look.
Screen Shot delmenu not available
You already understand what Clip does. In the same way, Delete is the DELETE command that you get when you press [DEL].
Try these things out, just to make sure. Choose the Do nothing option on the menu to get back to your program. Move the cursor to the argument i*i of the writeln instruction. Press [F10] and move the cursor if the argument isn't completely highlighted. Make sure you only highlight the i*i. Press [F3] to call up the Deletion Menu. Choose the Delete selection from this menu. Alice will get rid of the menu and you will see that the highlighted material has been deleted. Remember that DELETE doesn't leave a placeholder behind unless the placeholder is necessary for a correct program.
UNDO the deletion by pressing [CTRL-U]. You'll see the deleted i*i reappear. Now, CLIP out the i*i. You do exactly the same thing we did before, only this time you choose the Clip option from the Deletion Menu instead of Delete. The i*i is deleted again, but this time a Value placeholder is left behind.
You might ask, ``Why would I want to use the Deletion Menu when pressing [CTRL-P] or [DEL] is so much faster?'' Good question. If you can remember which button to push, pushing [CTRL-P] or [DEL] is faster. But what happens if you can't remember the right key? You can still work from the Menus, and that's the whole point.
It's also important to realize that some commands can't be executed just by pressing one or two keys. Some commands have to be executed from the menu (or in a third way that we haven't talked about yet). The Raise selection on the Delete Menu is an example of this sort of command.
In your program, highlight the for loop and its contents by moving the cursor to the for and pressing [F10]. Call up the Deletion Menu by pressing [F3] and choose the Raise selection. Notice what happens: the enclosing for statement disappears and the writeln that was inside is raised one level of indentation. In other words, Raise gets rid of a construct like for or if that encloses a number of statements. You have to highlight the enclosing statement before you can raise the contents.
Press [CTRL-U] twice to undo what we just did. We'll want the program in good shape for the sections to come.
The Clear this workspace gets rid of your current program and gives you a new empty program template. You can't UNDO this, so make sure you've saved your current program before you perform this operation.
The Recover memory selection cleans things up inside Alice to provide more memory for various purposes. The Recover memory command throws away all extraneous data stored in memory. In particular, it throws away all the information that is saved so that UNDO will work. This frees up a lot of memory but also means that you can't UNDO instructions that happened before the Recover operations. Alice warns you that this is the case.
We aren't going to talk about the Move to workspace selection just now -- we'll save that for next chapter when we talk about workspaces.
You get the Insertion Menu by selecting the Insertions entry from the Master Menu. You can also get the menu by pressing [F4]. Press [F4] now to have a look.
Screen Shot insmenu not available
The Extend list selection works exactly the same way as pressing [CTRL-E]. Move the cursor to the word writeln in the sample program, then press [F4] and select Extend list. You will see that Alice adds a new Statement placeholder after the writeln instruction. In the same way, Insert works the same way as pressing [INS]. Move the cursor to the word writeln, press [F4] and select Insert. You will see that Alice adds a new Statement placeholder before the writeln instruction.
Press [F4] again and this time choose the Possible Symbols selection. This provides a Symbol List in the same way that pressing [END] does. If you choose What can I type here? from the Insertion Menu, you will get the same sort of Input Menu that is provided by pressing [ALT-T].
The only things on the Insertion Menu that we haven't talked about yet are the Enclose and Get workspace selections. We'll talk about Get workspace in the next chapter. As for Enclose, why don't you see if you can understand how it works on your own? To get an explanation of this option, do what you always do: press [F9]. In this case, highlight the Enclose option on the menu and then press [F9] instead of another key. This will give you an explanation of what the command does. (Hint: it's the opposite of Raise on the Deletion Menu.)
You can get the Change Menu by choosing Change Structures from the Master Menu or by pressing [F5]. We aren't going to talk about anything on the Change Menu right now because we're saving it for the next chapter. However, if you want, you can call up the menu, highlight any selection on it, and press [F9] to get a description of what each command does.
The Move Menu contains a number of commands for moving the cursor around in your program. You can get the Move Menu by choosing Move Cursor from the Master Menu or by pressing [ALT-G].
Screen Shot movemenu not available
The Mark Position selection allows you to record a particular cursor location so that you can get back to it easily later on. To show how this works, move the cursor to the first actual instruction of your program (the one after the keyword begin). Press [ALT-G] to call the Move Menu, then choose Mark Position. At the bottom of the screen, you will see Alice type
Mark?
Alice wants you to give a name to this mark. The name of a mark is just a single letter, so let's call this one ``A''. Enter an ``A'' in response to Mark? -- you do not have to press [ENTER] after.
You won't see anything change in your program, but this cursor position is now marked with the name ``A''. To see that this is true, move the cursor anywhere else in the program. Next, press [ALT-G] and choose Go to mark. Alice will ask Mark? again. Enter ``A'' -- this says you want to go to mark ``A.'' The cursor will jump back to the position you marked.
The Former cursor loc selection is another way of jumping to an old cursor position. The cursor will jump to the position it had before the last command from the Move Menu. Try it -- press [ALT-G], and choose Former cursor loc. You'll see the cursor jump back to its previous position. Do it again, and the cursor will jump back to its second most recent position.
The Go to declaration command is useful when you want to check or change the declaration for a symbol (e.g. a variable). Place the cursor on a symbol name, then choose this command from the Move Menu. Alice will move the cursor up to the declaration for the symbol. When you are done looking at this declaration or changing it, you can get back to your former position with the Former cursor loc selection.
The Page down selection moves the cursor forward in your program. The distance it moves is about equal to the amount of material that can be shown on the terminal display screen. This allows you to ``page'' quickly through your program. You can also ``page down'' by pressing the [PgDn] key on the PC. The Page up selection is similar, but moves the cursor backwards. You can also ``page up'' by pressing the [PgUp] key on the PC.
The Up to Parent selection jumps to the start of whatever contains the current cursor location. For example, if the cursor is on the writeln of
for i := 1 to 10 do begin
writeln(i,i*i);
end;
choosing the Up to Parent selection would go to the for that contains the writeln instruction. You can also get this effect by pressing [CTRL-6]. (You can remember this by thinking that the ``^'' on the 6 key points up.)
The Top of Block selection goes to the start of the program or subprogram that contains the current cursor location. You can also get this effect by pressing [HOME].
This only leaves us with the Search commands. These allow you to search for strings of characters in your program. For example, suppose you want to find the next line that the variable hello is used in your program. You would begin by choosing the Search Forward selection from this menu. Alice would ask you what you wanted to search for and you would answer
hello
(then press [ENTER]). Alice would then look for the next instance of this string in your program. You can get the same effect by pressing [CTRL-F].
Search backward works the same way except that it looks backward through your program instead of forward. Search again searches for the last string that you were searching for. The search goes forward if the previous search was forward, and backwards otherwise. For example, if you wanted to search for the third occurrence of hello in your program, you might press [HOME] (to get to the start of the program), [CTRL-F] (to find the first occurrence), type in hello followed by [ENTER] to tell what you want to find, then use the Search again command twice.
Any time you issue a search command, it will indicate a default string to search for. This default will always be the last string you searched for. If you want to search for this default string, just press [ENTER]; otherwise, enter the string you want to look for.
The Run-Time Menu (also called the Debugging Menu) contains a number of commands that help you debug and run your programs. You can get the Run-Time Menu by choosing Running the Program from the Master Menu or by pressing [F6].
The entries on the Run-Time Menu will change, depending on how you have things set up. For example, there is an entry on the Run-Time Menu that turns debugging features on or off. If you have the debugging features on, the entry on the menu will let you turn them off. There's no point having an entry for turning these features on, because they already are on. If the debugging features are off, the entry on the menu will let you turn them on.
In this way, the selections on the Run-Time Menu depend on what you're doing. We'll give you a list of the possibilities here, but don't expect to see all of these when you press [F6]. Also note that this is not the order that the selections will be shown.
Big Step Cursor Following Off Cursor Following On Clear Point Continue Debug on Debug off Execute statement Immediate mode block Pop suspended state Pop suspended & Run Run Program Set Breakpoint Single Step Typecheck program Who called me? Write Output to Log File Don't Write Output to Log File
The Run Program selection runs your program in the same way that pressing [F1] does. The Single Step selection lets you single-step through your program. It is much easier to press [F2] again and again than to choose this selection from the Run-Time Menu every time you want Alice to execute another instruction; nevertheless, you can do this if you want.
The Cursor Following On selection is an interesting one. However, the program we're working with right now won't show how it works very well, so load the program ``sieve.ap'' from your Alice supplement disk (use the LOAD command). This program prints out the first few prime numbers.
Call up the Run-Time Menu by selecting it from the Master Menu or by pressing [F6]. Highlight the selection Cursor Following On and press the SPACE bar. Now, run your program by pressing [F1] or by choosing the Run Program selection from the Run-Time Menu. Alice will divide the screen into a source code half and an output half, the way it does when you are single-stepping. Watch what happens to the cursor on the screen. When Alice runs the program, it will move the cursor through your source code on the screen, showing you the instructions it is executing as it does them. In this way, you get a picture of your program as it runs. Run the program several times to make sure you see what's happening.
To turn off cursor following, call up the Run-Time Menu again and choose the Cursor Following Off selection. You can also choose the Debug off selection; this turns off cursor following and also gets rid of the ``split screen'' effect.
The Continue selection from the Run-Time Menu is a little tricky. We'll describe it in the next chapter.
You can call up the Miscellaneous Menu by choosing the Misc entry of the Master Menu or by pressing [SHIFT-F9]. The menu has the following entries.
Screen Shot miscmenu not available
The File I/O selection just calls up the Files Menu, the same way that [F8] does. The Redraw Screen selection rewrites everything that should be on the screen; this takes care of a few rare problems that foul up the screen display. The Autosave selection sets things up so that your program is automatically saved every time you change something in it (so that you don't have to use the SAVE command very often). As for the Change Workspace and Immediate selections, we'll talk about them in the next chapter. Special Changes are discussed in the next section, so that just leaves us with Set Macro.
The Set Macro selection lets you associate a series of keystrokes with a single key sequence. Once you've done this, you can type the key sequence any time in your Alice session and it will have the same effect as typing all the associated keystrokes.
For example, suppose you use readln instructions a lot and you want to save yourself some typing. You decide to associate the string of characters readln( with the single key R (upper case). To do this, press [SHIFT-F9] to summon the Miscellaneous Menu and choose the Set Macro selection.
Alice will first ask you for the single key sequence. You enter the upper case R. Next, Alice will ask you for the string of characters that should be associated with this sequence. You will type
readln(
followed by [ENTER] to show the end of the string. From this point onward, you can type R whenever you want to enter readln(. Try it and see. Move to a blank Statement placeholder, and enter R.
The Special Changes Menu listed in the Master Menu and several other menus contains commands that change one type of construction into another. For example, you can change an if statement into a while loop through the Special Changes Menu. Just put the cursor on the statement that you want to change and then call up the Special Changes Menu. You will be offered a list of the new statements that the old statement can become. Choose one of these, and Alice will make the change.
There is also a menu called the Select Menu, called up by pressing [SHIFT-F10]. This provides commands that can be applied to ranges that you have swept out; it is located on [SHIFT-F10] for convenience. All the commands on this menu are found on other menus too, so we won't talk about them here.
In this chapter, we talked about