! Wrong !
before [ ix;
Push:
print "Are you sure you want to do that?^";
print "^>";
ix = YesOrNo();
if (ix)
"Click.";
else
"Never mind, then.";
],
|
|
>push button Are you sure you want to do that? >no Never mind, then. >push button Are you sure you want to do that? >yes Click. |
Tidy and correct, right? Well, no. Consider:
|
>push button Are you sure you want to do that? >look Please answer yes or no.> undo Please answer yes or no.> quit Please answer yes or no.> no Never mind, then. |
This may look like "dumb player syndrome" in the transcript, but think
about it. The prompt printed before YesOrNo() looks
exactly like a normal command prompt. It's quite reasonable that a
"look" command should work. And certainly "undo" is a habitual way to
back out of screwed-up or dangerous situations. The player might try
"save" as well, or some entirely different command.
By the time the player looks at the screen and realizes that he's in a special prompt, he's pissed.
before [ ix;
Push:
print "Are you sure you want to do that?^";
print "Enter yes or no:>";
ix = YesOrNo();
if (ix)
"Click.";
else
"Never mind, then.";
],
|
|
>push button Are you sure you want to do that? Enter yes or no:>no Never mind, then. |
The prompt shown is chosen to be similar to the "Please answer yes or no"
library message. If you use a different prompt, you may want to change
that message too. (For inadequate reasons, it's Quit 1.)
YesOrNo() has an unobvious drawback. If the player
types "undo" after the command, the game jumps back to before the command
that called YesOrNo(). This is unintuitive; normally "undo"
jumps back one input, not two.
A nicer approach is not to use YesOrNo() at all. Instead,
watch for a Yes or No action on the next
turn. This allows the player to type any command, including "undo" or
"save", and the parser will behave in the expected way.
The code for this is left as an exercise. Sorry. :)
YesOrNo(), or any other routine that prompts
for a special input, make sure the player can tell he's not at a regular
command prompt.