feat: init basic pratter for #22

Author: phodal

chapi-domain/src/main/kotlin/chapi/domain/expr/Expression.kt

@@ -0,0 +1,67 @@
+package chapi.domain.expr
+
+import java.util.function.BinaryOperator
+import java.util.function.IntBinaryOperator
+
+// todo: mapping to pratt parser ?
+// mini sample <https://github.com/segeljakt/pratt>
+//
+// enum class TokenTree {
+//     Primary,
+//     Prefix,
+//     Infix,
+//     Postfix;
+// }
+sealed class Expression {
+    class BinOp(lhs: Expression, op: BinOpKind, rhs: Expression) : ExpressionNode
+    class UnOp(lhs: Expression, op: UnOpKind) : ExpressionNode
+    class Int(val value: Int?) : ExpressionNode
+}
+
+sealed class BinOpKind {
+    object Add : BinOpKind() // +
+    object Sub : BinOpKind() // -
+    object Mul : BinOpKind() // *
+    object Div : BinOpKind() // /
+    object Pow : BinOpKind() // ^
+    object Eq : BinOpKind() // =
+}
+
+sealed class UnOpKind {
+    object Not : UnOpKind() // !
+    object Neg : UnOpKind() // -
+    object Try : UnOpKind() // ?
+}
+
+interface ExpressionType {
+    val name: String
+}
+
+interface ExpressionNode {
+    val childrens: Array<ExpressionNode> get() = emptyArray()
+    val expressionTypes: Array<ExpressionType> get() = emptyArray()
+
+    fun getPriority(): Int = 0
+
+    fun addChildren(child: Operator) {
+        childrens.plus(child)
+    }
+
+    fun addExpressionType(type: ExpressionType) {
+        expressionTypes.plus(type)
+    }
+}
+
+
+interface Operator : ExpressionNode
+
+enum class Arithmetics : BinaryOperator<Int>, IntBinaryOperator {
+    PLUS {
+        override fun apply(t: Int, u: Int): Int {
+            return t + u
+        }
+    }
+    ;
+
+    override fun applyAsInt(t: Int, u: Int) = apply(t, u)
+}

chapi-domain/src/main/kotlin/chapi/domain/expr/TokenTree.kt

@@ -0,0 +1,10 @@
+package chapi.domain.expr
+
+import org.junit.jupiter.api.Test
+
+class ExpressionTest {
+    @Test
+    fun shouldAddChildren() {
+
+    }
+}