From 0507bfcc24ada2bdc52ad5ceadaafd4d7f0d0ccb Mon Sep 17 00:00:00 2001
From: darksnake <altavir@gmail.com>
Date: Thu, 11 Jun 2020 09:46:42 +0300
Subject: [PATCH] Expression simplification

---
 .../kmath/expressions/Expression.kt           |  9 -----
 .../kmath/expressions/SyntaxTreeNode.kt       | 32 ++++++++++++++---
 .../scientifik/kmath/operations/Algebra.kt    | 36 ++++++++++++++++---
 3 files changed, 60 insertions(+), 17 deletions(-)

diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/expressions/Expression.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/expressions/Expression.kt
index 73745f78f..aba7357e8 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/expressions/Expression.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/expressions/Expression.kt
@@ -24,13 +24,4 @@ interface ExpressionContext<T, E> : Algebra<E> {
      * A constant expression which does not depend on arguments
      */
     fun const(value: T): E
-}
-
-fun <T, E> ExpressionContext<T, E>.produce(node: SyntaxTreeNode): E {
-    return when (node) {
-        is NumberNode -> error("Single number nodes are not supported")
-        is SingularNode -> variable(node.value)
-        is UnaryNode -> unaryOperation(node.operation, produce(node.value))
-        is BinaryNode -> binaryOperation(node.operation, produce(node.left), produce(node.right))
-    }
 }
\ No newline at end of file
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/expressions/SyntaxTreeNode.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/expressions/SyntaxTreeNode.kt
index b4038f680..e56165aad 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/expressions/SyntaxTreeNode.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/expressions/SyntaxTreeNode.kt
@@ -1,11 +1,25 @@
 package scientifik.kmath.expressions
 
+import scientifik.kmath.operations.NumericAlgebra
+
+/**
+ * A syntax tree node for mathematical expressions
+ */
 sealed class SyntaxTreeNode
 
+/**
+ * A node containing unparsed string
+ */
 data class SingularNode(val value: String) : SyntaxTreeNode()
 
+/**
+ * A node containing a number
+ */
 data class NumberNode(val value: Number) : SyntaxTreeNode()
 
+/**
+ * A node containing an unary operation
+ */
 data class UnaryNode(val operation: String, val value: SyntaxTreeNode) : SyntaxTreeNode() {
     companion object {
         const val ABS_OPERATION = "abs"
@@ -17,12 +31,22 @@ data class UnaryNode(val operation: String, val value: SyntaxTreeNode) : SyntaxT
     }
 }
 
+/**
+ * A node containing binary operation
+ */
 data class BinaryNode(val operation: String, val left: SyntaxTreeNode, val right: SyntaxTreeNode) : SyntaxTreeNode() {
-    companion object {
-        //TODO add operations
-    }
+    companion object
 }
 
 //TODO add a function with positional arguments
 
-//TODO add a function with named arguments
\ No newline at end of file
+//TODO add a function with named arguments
+
+fun <T> NumericAlgebra<T>.compile(node: SyntaxTreeNode): T{
+    return when (node) {
+        is NumberNode -> number(node.value)
+        is SingularNode -> raw(node.value)
+        is UnaryNode -> unaryOperation(node.operation, compile(node.value))
+        is BinaryNode -> binaryOperation(node.operation, compile(node.left), compile(node.right))
+    }
+}
\ No newline at end of file
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/operations/Algebra.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/operations/Algebra.kt
index b3282e5f3..c9fbc1c8b 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/operations/Algebra.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/operations/Algebra.kt
@@ -7,10 +7,35 @@ annotation class KMathContext
  * Marker interface for any algebra
  */
 interface Algebra<T> {
+    /**
+     * Wrap raw string or variable
+     */
+    fun raw(value: String): T = error("Wrapping of '$value' is not supported in $this")
+
+    /**
+     * Dynamic call of unary operation with name [operation] on [arg]
+     */
     fun unaryOperation(operation: String, arg: T): T
+
+    /**
+     * Dynamic call of binary operation [operation] on [left] and [right]
+     */
     fun binaryOperation(operation: String, left: T, right: T): T
 }
 
+/**
+ * An algebra with numeric representation of members
+ */
+interface NumericAlgebra<T> : Algebra<T> {
+    /**
+     * Wrap a number
+     */
+    fun number(value: Number): T
+}
+
+/**
+ * Call a block with an [Algebra] as receiver
+ */
 inline operator fun <A : Algebra<*>, R> A.invoke(block: A.() -> R): R = run(block)
 
 /**
@@ -87,7 +112,7 @@ interface RingOperations<T> : SpaceOperations<T> {
         else -> super.binaryOperation(operation, left, right)
     }
 
-    companion object{
+    companion object {
         const val TIMES_OPERATION = "*"
     }
 }
@@ -95,13 +120,16 @@ interface RingOperations<T> : SpaceOperations<T> {
 /**
  * The same as {@link Space} but with additional multiplication operation
  */
-interface Ring<T> : Space<T>, RingOperations<T> {
+interface Ring<T> : Space<T>, RingOperations<T>, NumericAlgebra<T> {
     /**
      * neutral operation for multiplication
      */
     val one: T
 
-//    operator fun T.plus(b: Number) = this.plus(b * one)
+    override fun number(value: Number): T = one * value.toDouble()
+
+    // those operators are blocked by type conflict in RealField
+    //    operator fun T.plus(b: Number) = this.plus(b * one)
 //    operator fun Number.plus(b: T) = b + this
 //
 //    operator fun T.minus(b: Number) = this.minus(b * one)
@@ -121,7 +149,7 @@ interface FieldOperations<T> : RingOperations<T> {
         else -> super.binaryOperation(operation, left, right)
     }
 
-    companion object{
+    companion object {
         const val DIV_OPERATION = "/"
     }
 }