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CA2
Tracing Code (1 point)
1 + 2 * 3 - 4 factorial -15
a := #(1 2 3 4 5) #(1 2 3 4 5)
a select: [:i | i odd] #(1 3 5)
b := a #(1 2 3 4 5)
a := a reversed #(5 4 3 2 1)
b collect: [:i | i i] #(1 4 9 16 25)
a perform: #at: withArguments: #(4) 2
Message Passing (1 point)
while loop
Java:
while (aBooleanTest)
{
// do stuff
}
Squeak:
[aBooleanTest]
whileTrue: ["do stuff"].
Example:
x := 0.
[ (x < 10) ]
whileTrue: [Transcript show: (x) printString.
Transcript show: ' '.
x := x + 1.].
"whileTrue" is a message sent to boolean values. "x <10" will return either true or false.
The block of code after "whileTrue:" are arguments.
for loop
Java:
for (i = 1; i <= 10; i++)
{
// do stuff
}
Squeak:
1 to: 10 by: 1 do: [" stuff "].
Example:
1 to: 10 by: 1 do: [:x | Transcript show: 'Hello '.].
Message "1 to: 10 by: 1 do:" is sent to the object 1. The block of code after "..do:" are arguments.
if/then/else
Java:
if (aBooleanTest)
{ // do stuff
}
else
{ // do stuff
}
Squeak:
(aBooleanTest)
ifTrue: [" do stuff"]
ifFalse: [" do stuff"]
Example:
a := 0.
b := 0.
(a = b)
ifTrue: [Transcript show: 'A and B are equal'; cr.]
ifFalse: [Transcript show: 'A and B are NOT equal'; cr.].
"ifTrue" and "ifFalse" are messages sent to boolean values. "a = b" will return either true or false.
The block of code after "ifTrue:" and the block of code after "ifFalse" are arguments
for true and false case, respectively.
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