Page 225 - Learn To Program With Scratch

In each iteration of the loop, the Driver sprite asks the player to guess
a letter and waits for input w. When the player enters a guess, the script
calls ProcessAnswer, which will update a flag (named gotLetter) to indicate
whether the letter was right or wrong.
When ProcessAnswer returns, the script checks the gotLetter flag x and
acts based on whether the player’s guess was correct or not. I’ll explain the
procedures called by NewGame next, starting with the scripts in Figure 8-26.

Belongs to the Belongs to the
Driver sprite Helper sprite

Belongs to the
Hangman sprite

Figure 8-26: Scripts triggered from the Initialize procedure

During initialization, the Driver sprite hides itself, initializes displayWord
to a string with six question marks, and sets remAttempts (how many guesses
the player has left) to 8. It then selects the secretWord from a predefined
list of six-letter words. Next the procedure broadcasts Update so the Helper
sprite will assign its variables (whose monitors are visible on the Stage) to
the correct values. The last instruction broadcasts the Reset message to the
Hangman sprite. When the Hangman sprite receives this message, it switches
to its start costume, which shows an empty gallows.
Now let’s consider a simple example to help us understand what the
ProcessAnswer procedure does (see Figure 8-27). Assume the secret
word is across and that this is the first round of the game (which means
that displayWord is “??????”). If the player’s first guess is r, ProcessAnswer
should set gotLetter to 1 to indicate a correct guess, set displayWord to “??r???”
to show the letter’s position, and set qmarkCount (the number of question
marks in the updated display string) to 5. When qmarkCount reaches 0, the
player has guessed all the letters in the secret word. ProcessAnswer belongs
to the Driver sprite, and you can see the full script in Figure 8-27 (left).
ProcessAnswer starts by resetting both the gotLetter flag and qmarkCount
to 0. It will increase qmarkCount by 1 for every unknown letter in the secret
word. The temporary variable, temp, which is used to construct the display
string after every guess, is initialized to an empty string. The pos variable is
used as a loop counter.

String Processing 203

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