feat: initilize code snippet for metaprogramming

Author: draveness

.gitignore

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+a.out
+macro
+macro_with_hash

Makefile

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+c:
+	gcc example.c && ./a.out
+
+c1:
+	gcc macro.c && ./a.out
+
+c2:
+	gcc macro_problem.c && ./a.out
+
+c2e:
+	gcc -E macro_problem.c
+
+h1:
+	gcc hygiene_macro.c && ./a.out
+
+h1e:
+	gcc -E hygiene_macro.c
+
+c3:
+	gcc macro_with_paren.c && ./a.out
+
+e1:
+	iex macro.exs
+
+r1:
+	rustc macro.rs && ./macro
+
+r2:
+	rustc macro_with_hash.rs && ./macro_with_hash
+

car.rb

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+class CarModel
+  def engine_info=(info)
+    @engine_info = info
+  end
+
+  def engine_info
+    @engine_info
+  end
+
+  def engine_price=(price)
+    @engine_price = price
+  end
+
+  def engine_price
+    @engine_price
+  end
+
+  def wheel_info=(info)
+    @wheel_info = info
+  end
+
+  def wheel_info
+    @wheel_info
+  end
+
+  def wheel_price=(price)
+    @wheel_price = price
+  end
+
+  def wheel_price
+    @wheel_price
+  end
+
+  def airbag_info=(info)
+    @airbag_info = info
+  end
+
+  def airbag_info
+    @airbag_info
+  end
+
+  def airbag_price=(price)
+    @airbag_price = price
+  end
+
+  def airbag_price
+    @airbag_price
+  end
+
+  def alarm_info=(info)
+    @alarm_info = info
+  end
+
+  def alarm_info
+    @alarm_info
+  end
+
+  def alarm_price=(price)
+    @alarm_price = price
+  end
+
+  def alarm_price
+    @alarm_price
+  end
+
+  def stereo_info=(info)
+    @stereo_info = info
+  end
+
+  def stereo_info
+    @stereo_info
+  end
+
+  def stereo_price=(price)
+    @stereo_price = price
+  end
+
+  def stereo_price
+    @stereo_price
+  end
+end

car_with_macro.rb

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+class CarModel
+  FEATURES = ["engine", "wheel", "airbag", "alarm", "stereo"]
+
+  FEATURES.each do |feature|
+    define_method("#{feature}_info=") do |info|
+      instance_variable_set("@#{feature}_info", info)
+    end
+
+    define_method("#{feature}_info") do
+      instance_variable_get("@#{feature}_info")
+    end
+
+    define_method "feature_price=" do |price|
+      instance_variable_set("@#{feature}_price", price)
+    end
+
+    define_method("#{feature}_price") do
+      instance_variable_get("@#{feature}_price")
+    end
+  end
+end

echo/echo

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+package main
+
+//go:generate echo "hello world"
+func main() {
+}

echo/main.go

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+#include <stdio.h>
+#include <stdlib.h>
+
+int main() {
+    for (int i = 0; i < 10; i++) {
+        char *echo = (char*)malloc(6 *sizeof(char));
+        sprintf(echo, "echo %d", i);
+        system(echo);
+    }
+
+    return 0;
+}

example.c

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+class MyGhostClass
+  def method_missing(name, *args)
+    puts "#{name} was called with arguments: #{args.join(',')}"
+  end
+end
+
+m = MyGhostClass.new
+m.awesome_method("one", "two")
+m.another_method("three", "four")

ghost_class.rb

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+#include <stdio.h>
+
+#define inc(i) do { int a = 0; ++i; } while(0)
+
+int main() {
+    int a = 4, b = 8;
+    inc(a);
+    inc(b);
+    printf("%d, %d\n", a, b); // => 4, 9 !!
+    return 0;
+}

hygiene_macro.c

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+#include <stdio.h>
+
+#define add(a, b) a + b
+
+int main() {
+    int a = 1;
+    int b = 2;
+    printf("%d + %d = %d\n", a, b, add(a, b));
+}

macro.c

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+defmodule Unless do
+  def fun_unless(clause, do: expression) do
+    if(!clause, do: expression)
+  end
+
+  defmacro macro_unless(clause, do: expression) do
+    quote do
+      if(!unquote(clause), do: unquote(expression))
+    end
+  end
+end

macro.exs

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+macro_rules! yo {
+    ($name:expr) => {
+       println!("Yo {}!", $name);
+    };
+}
+
+fn main() {
+    yo!("Draven")
+}

macro.rs

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+#include <stdio.h>
+
+#define add(a, b) a+b
+
+int main() {
+    int a = 1;
+    int b = 2;
+    int c = 3;
+    printf("(%d + %d) * %d = %d\n", a, b, c, add(a, b) * c);
+}

macro_problem.c

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+use std::collections::HashMap;
+
+macro_rules! map {
+    ($( $key:expr => $value:expr ),*) => {{
+        let mut hm = HashMap::new();
+        $(hm.insert($key, $value); )*;
+        hm
+    }};
+}
+
+fn main() {
+    let user = map!(
+        "name" => "Draven",
+        "gender" => "Male"
+    );
+
+    println!("Userr {:?}", user);
+}

macro_with_hash.rs

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+#include <stdio.h>
+
+#define add(a, b) ((a)+(b))
+
+int main() {
+    int a = 1;
+    int b = 2;
+    int c = 3;
+    printf("(%d + %d) * %d = %d\n", a, b, c, add(a, b) * c);
+}

macro_with_more_paren.c

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+#include <stdio.h>
+
+#define add(a, b) (a+b)
+
+int main() {
+    int a = 1;
+    int b = 2;
+    int c = 3;
+    printf("(%d + %d) * %d = %d\n", a, b, c, add(a, b) * c);
+}

macro_with_paren.c

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+package painkiller
+
+//go:generate stringer -type=Pill
+type Pill int
+
+const (
+	Placebo Pill = iota
+	Aspirin
+	Ibuprofen
+	Paracetamol
+	Acetaminophen = Paracetamol
+)

pill/pill.go

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+IO.puts "with function"
+Unless.fun_unless true, do: IO.puts "this should never be printed"

pill/pill_string.go

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+IO.puts "with macro"
+Unless.macro_unless true, do: IO.puts "this should never be printed"
+
+# expr = quote do: Unless.macro_unless(true, do: IO.puts "this should never be printed")
+# Macro.expand_once(expr, __ENV__)