Metaprogramming with the Boo programming language.

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4. • template<int n> struct Factorial
{
enum {
RET = n *
Factorial<n-1>::RET
• }
};
template<> struct Factorial<0>
{
enum {
• RET = 1
}
};
⋮
int n = Factorial<5>::RET; // 120

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– #define sqr(x) ((x)*(x))
int n = sqr(2);
// emits int n = ((2)*(2)); –
• #define
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pow(x,n)
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9. class • MyMacro
MyMacro(AbstractAstMacro)
{
override def Expand • MyMacro 1 2
(macro as MacroStatement)
{
// macro.Argument[n] • MyMacro:
// macro.Body print “test”
yield/return
}
}

10. class
MyMacro(AbstractAstMacro)
{
macro MyMacro (n as int):
override def Expand
(macro as MacroStatement) // MyMacro.Argument[n]
{ // MyMacro.Body
// macro.Argument[0] yield/return
// macro.Body
yield/return
}
}

11. k
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13. macro dateNow:
now = DateTime.Now
return [|
print $(now.ToLocalTime().ToString())
|]

14. macro RepeatCStyle(c as int): macro RepeatInline(c as int):
return [| body = RepeatInline.Body
for i in range($c): yieldAll body for i in range(c)
$(RepeatCStyle.Body)
|]
RepeatXxx 3:
print “Go”
int ___temp14 = 0; Console.WriteLine("Go");
while (___temp14 < 3) Console.WriteLine("Go");
{ Console.WriteLine("Go");
int i = ___temp14;
___temp14++;
Console.WriteLine("Go");
}

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16. [meta] def assert(condition as Expression):
return [|
if not $condition:
raise AssertionFailedException( 
$(condition.ToCodeString()))
|]

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18. public class 
TimestampAttribute(AbstractAstAttribute):
public override def Apply(node as Node):
c = node as ClassDefinition
now = DateTime.Now
m = [|
public def GetTimestamp():
return $(now.ToLocalTime().ToString())
|]
c.Members.Add(m) // a new member added to
// an existing class

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– [Timestamp]
public class C:
public def constructor():
pass
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– c = C()
print c.GetTimestamp()

21. j
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