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Compile-time calculation: Difference between revisions
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If we compile this with <code>rustc factorial.rs -O --emit asm</code> and inspect the outputted assembly, we can see <code>movq $3628800, (%rsp)</code>. This means the result of 3628800 was calculated in compile-time rather than run-time.
=={{header|Scala}}==
<lang Scala>object Main extends {
val tenFactorial = 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2
def tenFac = 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2
println(s"10! = $tenFactorial", tenFac)
}</lang>
As it can been seen in the always heavily optimized run-time code the calculations are already computed for the field constant and function method.
<pre>
public int tenFac();
descriptor: ()I
flags: (0x0001) ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: ldc #28 // int 3628800
2: ireturn
LocalVariableTable:
Start Length Slot Name Signature
0 3 0 this L$line2/$read$$iw$$iw$Main$;
LineNumberTable:
line 14: 0
public $line2.$read$$iw$$iw$Main$();
descriptor: ()V
flags: (0x0001) ACC_PUBLIC
Code:
stack=6, locals=1, args_size=1
0: aload_0
1: invokespecial #29 // Method java/lang/Object."<init>":()V
4: aload_0
5: putstatic #31 // Field MODULE$:L$line2/$read$$iw$$iw$Main$;
8: aload_0
9: ldc #28 // int 3628800
11: putfield #25 // Field tenFactorial:I
14: getstatic #36 // Field scala/Predef$.MODULE$:Lscala/Predef$;
17: new #38 // class scala/Tuple2
20: dup
21: new #40 // class java/lang/StringBuilder</pre>
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