kmizu

case class Add(l: Tree, r: Tree) extends Tree
case class Sub(l: Tree, r: Tree) extends Tree
case class Mul(l: Tree, r: Tree) extends Tree
case class Div(l: Tree, r: Tree) extends Tree
case class Num(v: Int) extends Tree

// switch ≒ match
def eval(tree: Tree): Int = tree match {
  case Add(l, r) =>  eval(l) + eval(r)
  case Sub(l, r) =>  eval(l) - eval(r)

kmizu

class Hello {
  def return100: Int = {
    for(i <- 1 to 1000) 
      if(i == 100) return 100
    0
  }
}

kmizu

import {
  com.pi4j.io.i2c.I2CBus;
  com.pi4j.io.i2c.I2Device;
  com.pi4j.io.i2c.I2CFactory;
  java.io.IOException;
}

def up(x: Byte): Int {
  return x;
}

kmizu

scalaVersion := "2.13.1"
name := "pi4r"
version := "0.0.1-SNAPSHOT"
libraryDependencies ++= Seq(
  "com.pi4j" % "pi4j-core" % "1.2",
  "com.pi4j" % "pi4j-device" % "1.2",
  "com.pi4j" % "pi4j-gpio-extension" % "1.2",
  "com.pi4j" % "pi4j-service" % "1.1",
  "com.pi4j" % "pi4j-native" % "1.2" pomOnly()
)

kmizu

public class Fact {
  public static int fact(int n) {
    if(i < 0) throw new IllegalArgumentException("n must be >= 0");
    int r = 1;
    for(int i = 1; i <= n; i++) {
      r *= i;
    } 
    return r;
  }
}

kmizu

import scala.reflect.macros.whitebox.Context
import scala.language.experimental.macros

object Macros {
  def test(body: Any*): Unit = macro testImpl
  def testImpl(c: Context)(body: c.Expr[Any]*) : c.Expr[Unit] = {
    import c.universe._
    for(expr <- body) {
      print("expr is ")
      expr.tree match {

kmizu

import scala.reflect.macros.whitebox.Context
import scala.language.experimental.macros

object Macros {
  def reverse(id: Any): Any = macro reverseImpl
  def reverseImpl(c: Context)(id: c.Expr[Any]) : c.Expr[Any] = {
    import c.universe._
    println(id)
    println(id.tree)
    println(id.getClass)

kmizu

import scala.reflect.macros.whitebox.Context
import scala.language.experimental.macros

object Macros {
  def reverse(id: Any): Any = macro reverseImpl
  def reverseImpl(c: Context)(id: c.Expr[Any]) : c.Expr[Any] = {
    import c.universe._
    val Ident(TermName(name)) = id.tree
    c.Expr[Any](Ident(TermName(name.reverse)))
  }

kmizu

import scala.reflect.macros.whitebox.Context
import scala.language.experimental.macros

object Macros {
  // 文字列をコンパイル時に反転させるマクロ
  def reverse(str: String): String = macro reverseImpl
  // マクロの実装
  def reverseImpl(c: Context)(str: c.Expr[String]) : c.Expr[String] = {
    import c.universe._
    val Literal(Constant(s:String)) = str.tree

kmizu

case class Point(x: Int, y: Int)
def traverse(p: Point): Int = p match {
  case Point(3, 3) => 
    1
  case Point(x, y) if x <= 3 && y <= 3 =>
    traverse(p.copy(x = p.x + 1)) +
    traverse(p.copy(y = p.y + 1))
  case Point(_, _) =>
    0
}