Redesign exponential function rendering

kmath-ast/src/commonMain/kotlin/space/kscience/kmath/ast/rendering/LatexSyntaxRenderer.kt

@@ -71,6 +71,15 @@ public object LatexSyntaxRenderer : SyntaxRenderer {
                 append('}')
             }
 
+            is ExponentSyntax -> if (node.useOperatorForm) {
+                append("\\operatorname{exp}\\,")
+                render(node.operand)
+            } else {
+                append("e^{")
+                render(node.operand)
+                append('}')
+            }
+
             is SuperscriptSyntax -> {
                 render(node.left)
                 append("^{")

kmath-ast/src/commonMain/kotlin/space/kscience/kmath/ast/rendering/MathMLSyntaxRenderer.kt

@@ -82,6 +82,19 @@ public object MathMLSyntaxRenderer : SyntaxRenderer {
 
             is RadicalSyntax -> tag("msqrt") { render(node.operand) }
 
+            is ExponentSyntax -> if (node.useOperatorForm) {
+                tag("mo") { append("exp") }
+                tag("mspace", "width" to "0.167em")
+                render(node.operand)
+            } else {
+                tag("msup") {
+                    tag("mrow") {
+                        tag("mi") { append("e") }
+                    }
+                    tag("mrow") { render(node.operand) }
+                }
+            }
+
             is SuperscriptSyntax -> tag("msup") {
                 tag("mrow") { render(node.left) }
                 tag("mrow") { render(node.right) }

kmath-ast/src/commonMain/kotlin/space/kscience/kmath/ast/rendering/MathRenderer.kt

@@ -83,7 +83,7 @@ public open class FeaturedMathRendererWithPostProcess(
                 Fraction.Default,
                 Power.Default,
                 SquareRoot.Default,
-                Exponential.Default,
+                Exponent.Default,
                 InverseTrigonometricOperations.Default,
 
                 // Fallback option for unknown operations - printing them as operator
@@ -100,6 +100,7 @@ public open class FeaturedMathRendererWithPostProcess(
                 PrintSymbolic,
             ),
             listOf(
+                BetterExponent,
                 SimplifyParentheses.Default,
                 BetterMultiplication,
             ),

kmath-ast/src/commonMain/kotlin/space/kscience/kmath/ast/rendering/MathSyntax.kt

@@ -189,6 +189,24 @@ public data class RadicalSyntax(
     }
 }
 
+/**
+ * Represents exponential function.
+ *
+ * @property operand The argument of function.
+ * @property useOperatorForm `true` if operator form is used (*exp (x)*), `false` if exponentiation form is used
+ * (*e<sup>x</sup>*).
+ * @author Iaroslav Postovalov
+ */
+public data class ExponentSyntax(
+    public override val operation: String,
+    public override val operand: OperandSyntax,
+    public var useOperatorForm: Boolean,
+) : UnarySyntax() {
+    init {
+        operand.parent = this
+    }
+}
+
 /**
  * Represents a syntax node with superscript (usually, for exponentiation).
  *

kmath-ast/src/commonMain/kotlin/space/kscience/kmath/ast/rendering/features.kt

@@ -56,10 +56,14 @@ private fun printSignedNumberString(s: String): MathSyntax {
 public class PrettyPrintFloats(public val types: Set<KClass<out Number>>) : RenderFeature {
     public override fun render(renderer: FeaturedMathRenderer, node: MST): MathSyntax? {
         if (node !is MST.Numeric || node.value::class !in types) return null
-        val toString = node.value.toString().removeSuffix(".0")
+        val toString = when (val v = node.value) {
+            is Float -> v.multiplatformToString()
+            is Double -> v.multiplatformToString()
+            else -> v.toString()
+        }.removeSuffix(".0")
 
-        if ('E' in toString) {
+        if (toString.contains('E', ignoreCase = true)) {
-            val (beforeE, afterE) = toString.split('E')
+            val (beforeE, afterE) = toString.split('E', ignoreCase = true)
             val significand = beforeE.toDouble().toString().removeSuffix(".0")
             val exponent = afterE.toDouble().toString().removeSuffix(".0")
 
@@ -108,9 +112,7 @@ public class PrettyPrintFloats(public val types: Set<KClass<out Number>>) : Rend
  */
 public class PrettyPrintIntegers(public val types: Set<KClass<out Number>>) : RenderFeature {
     public override fun render(renderer: FeaturedMathRenderer, node: MST): MathSyntax? {
-        if (node !is MST.Numeric || node.value::class !in types)
+        if (node !is MST.Numeric || node.value::class !in types) return null
-            return null
-
         return printSignedNumberString(node.value.toString())
     }
 
@@ -282,15 +284,15 @@ public class SquareRoot(operations: Collection<String>?) : Unary(operations) {
     }
 }
 
-public class Exponential(operations: Collection<String>?) : Unary(operations) {
+public class Exponent(operations: Collection<String>?) : Unary(operations) {
-    public override fun render0(parent: FeaturedMathRenderer, node: MST.Unary): MathSyntax = SuperscriptSyntax(
+    public override fun render0(parent: FeaturedMathRenderer, node: MST.Unary): MathSyntax = ExponentSyntax(
         operation = node.operation,
-        left = SymbolSyntax(string = "e"),
+        operand = OperandSyntax(operand = parent.render(node.value), parentheses = true),
-        right = parent.render(node.value),
+        useOperatorForm = true,
     )
 
     public companion object {
-        public val Default: Exponential = Exponential(setOf(ExponentialOperations.EXP_OPERATION))
+        public val Default: Exponent = Exponent(setOf(ExponentialOperations.EXP_OPERATION))
     }
 }
 

kmath-ast/src/commonMain/kotlin/space/kscience/kmath/ast/rendering/multiplatformToString.kt

@@ -0,0 +1,9 @@
+/*
+ * Copyright 2018-2021 KMath contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package space.kscience.kmath.ast.rendering
+
+internal expect fun Double.multiplatformToString(): String
+internal expect fun Float.multiplatformToString(): String

kmath-ast/src/commonMain/kotlin/space/kscience/kmath/ast/rendering/stages.kt

@@ -16,8 +16,7 @@ import space.kscience.kmath.operations.RingOperations
  * @author Iaroslav Postovalov
  */
 public object BetterMultiplication : FeaturedMathRendererWithPostProcess.PostProcessStage {
-    public override fun perform(node: MathSyntax) {
+    public override fun perform(node: MathSyntax): Unit = when (node) {
-        when (node) {
         is NumberSyntax -> Unit
         is SymbolSyntax -> Unit
         is OperatorNameSyntax -> Unit
@@ -32,6 +31,7 @@ public object BetterMultiplication : FeaturedMathRendererWithPostProcess.PostPro
         is UnaryPlusSyntax -> perform(node.operand)
         is UnaryMinusSyntax -> perform(node.operand)
         is RadicalSyntax -> perform(node.operand)
+        is ExponentSyntax -> perform(node.operand)
 
         is SuperscriptSyntax -> {
             perform(node.left)
@@ -79,6 +79,47 @@ public object BetterMultiplication : FeaturedMathRendererWithPostProcess.PostPro
             perform(node.right)
         }
     }
+}
+
+
+/**
+ * Applies [ExponentSyntax.useOperatorForm] to [ExponentSyntax] when the operand contains a fraction, a
+ * superscript or a subscript to improve readability.
+ *
+ * @author Iaroslav Postovalov
+ */
+public object BetterExponent : FeaturedMathRendererWithPostProcess.PostProcessStage {
+    private fun perform0(node: MathSyntax): Boolean {
+        return when (node) {
+            is NumberSyntax -> false
+            is SymbolSyntax -> false
+            is OperatorNameSyntax -> false
+            is SpecialSymbolSyntax -> false
+            is OperandSyntax -> perform0(node.operand)
+            is UnaryOperatorSyntax -> perform0(node.prefix) || perform0(node.operand)
+            is UnaryPlusSyntax -> perform0(node.operand)
+            is UnaryMinusSyntax -> perform0(node.operand)
+            is RadicalSyntax -> perform0(node.operand)
+
+            is ExponentSyntax -> {
+                val r = perform0(node.operand)
+                node.useOperatorForm = r
+                r
+            }
+
+            is SuperscriptSyntax -> true
+            is SubscriptSyntax -> true
+            is BinaryOperatorSyntax -> perform0(node.prefix) || perform0(node.left) || perform0(node.right)
+            is BinaryPlusSyntax -> perform0(node.left) || perform0(node.right)
+            is BinaryMinusSyntax -> perform0(node.left) || perform0(node.right)
+            is FractionSyntax -> true
+            is RadicalWithIndexSyntax -> perform0(node.left) || perform0(node.right)
+            is MultiplicationSyntax -> perform0(node.left) || perform0(node.right)
+        }
+    }
+
+    public override fun perform(node: MathSyntax) {
+        perform0(node)
     }
 }
 
@@ -90,8 +131,7 @@ public object BetterMultiplication : FeaturedMathRendererWithPostProcess.PostPro
  */
 public class SimplifyParentheses(public val precedenceFunction: (MathSyntax) -> Int) :
     FeaturedMathRendererWithPostProcess.PostProcessStage {
-    public override fun perform(node: MathSyntax) {
+    public override fun perform(node: MathSyntax): Unit = when (node) {
-        when (node) {
         is NumberSyntax -> Unit
         is SymbolSyntax -> Unit
         is OperatorNameSyntax -> Unit
@@ -116,8 +156,11 @@ public class SimplifyParentheses(public val precedenceFunction: (MathSyntax) ->
                 else -> precedence > precedenceFunction(parent)
             }
 
+            val isInsideExpOperator =
+                node.parent is ExponentSyntax && (node.parent as ExponentSyntax).useOperatorForm
+
             node.parentheses = !isRightOfSuperscript
-                        && (needParenthesesByPrecedence || node.parent is UnaryOperatorSyntax)
+                    && (needParenthesesByPrecedence || node.parent is UnaryOperatorSyntax || isInsideExpOperator)
 
             perform(node.operand)
         }
@@ -128,10 +171,9 @@ public class SimplifyParentheses(public val precedenceFunction: (MathSyntax) ->
         }
 
         is UnaryPlusSyntax -> perform(node.operand)
-            is UnaryMinusSyntax -> {
+        is UnaryMinusSyntax -> perform(node.operand)
-                perform(node.operand)
-            }
         is RadicalSyntax -> perform(node.operand)
+        is ExponentSyntax -> perform(node.operand)
 
         is SuperscriptSyntax -> {
             perform(node.left)
@@ -174,7 +216,6 @@ public class SimplifyParentheses(public val precedenceFunction: (MathSyntax) ->
             perform(node.right)
         }
     }
-    }
 
     public companion object {
         /**

kmath-ast/src/commonTest/kotlin/space/kscience/kmath/ast/ParserPrecedenceTest.kt

@@ -3,7 +3,7 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
-package space.kscisnce.kmath.ast
+package space.kscience.kmath.ast
 
 import space.kscience.kmath.ast.parseMath
 import space.kscience.kmath.expressions.evaluate

kmath-ast/src/commonTest/kotlin/space/kscience/kmath/ast/ParserTest.kt

@@ -3,9 +3,8 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
-package space.kscisnce.kmath.ast
+package space.kscience.kmath.ast
 
-import space.kscience.kmath.ast.parseMath
 import space.kscience.kmath.complex.Complex
 import space.kscience.kmath.complex.ComplexField
 import space.kscience.kmath.expressions.evaluate

kmath-ast/src/commonTest/kotlin/space/kscience/kmath/ast/rendering/TestFeatures.kt

@@ -42,6 +42,22 @@ internal class TestFeatures {
         testLatex(Numeric(1.1e-10), "1.1\\times10^{-10}")
         testLatex(Numeric(-1.1e-10), "-1.1\\times10^{-10}")
         testLatex(Numeric(-1.1e10), "-1.1\\times10^{10}")
+        testLatex(Numeric(0.001), "0.001")
+        testLatex(Numeric(0.0000001), "1\\times10^{-7}")
+
+        testLatex(Numeric(Float.NaN), "NaN")
+        testLatex(Numeric(Float.POSITIVE_INFINITY), "\\infty")
+        testLatex(Numeric(Float.NEGATIVE_INFINITY), "-\\infty")
+        testLatex(Numeric(1.0f), "1")
+        testLatex(Numeric(-1.0f), "-1")
+        testLatex(Numeric(1.42f), "1.42")
+        testLatex(Numeric(-1.42f), "-1.42")
+        testLatex(Numeric(1e10f), "1\\times10^{10}")
+        testLatex(Numeric(1e-10f), "1\\times10^{-10}")
+        testLatex(Numeric(-1e-10f), "-1\\times10^{-10}")
+        testLatex(Numeric(-1e10f), "-1\\times10^{10}")
+        testLatex(Numeric(0.001f), "0.001")
+        testLatex(Numeric(0.0000001f), "1\\times10^{-7}")
     }
 
     @Test

kmath-ast/src/commonTest/kotlin/space/kscience/kmath/ast/rendering/TestStages.kt

@@ -30,4 +30,11 @@ internal class TestStages {
         testLatex("(x+x)^x+x*x", "\\left(x+x\\right)^{x}+x\\,x")
         testLatex("x^(x+x)", "x^{x+x}")
     }
+
+    @Test
+    fun exponent() {
+        testLatex("exp(x)", "e^{x}")
+        testLatex("exp(x/2)", "\\operatorname{exp}\\,\\left(\\frac{x}{2}\\right)")
+        testLatex("exp(x^2)", "\\operatorname{exp}\\,\\left(x^{2}\\right)")
+    }
 }

kmath-ast/src/jsMain/kotlin/space/kscience/kmath/ast/rendering/multiplatformToString.kt

@@ -0,0 +1,18 @@
+/*
+ * Copyright 2018-2021 KMath contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package space.kscience.kmath.ast.rendering
+
+internal actual fun Double.multiplatformToString(): String {
+    val d = this
+    if (d >= 1e7 || d <= -1e7) return js("d.toExponential()") as String
+    return toString()
+}
+
+internal actual fun Float.multiplatformToString(): String {
+    val d = this
+    if (d >= 1e7f || d <= -1e7f) return js("d.toExponential()") as String
+    return toString()
+}

kmath-ast/src/jvmMain/kotlin/space/kscience/kmath/ast/rendering/multiplatformToString.kt

@@ -0,0 +1,9 @@
+/*
+ * Copyright 2018-2021 KMath contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package space.kscience.kmath.ast.rendering
+
+internal actual fun Double.multiplatformToString(): String = toString()
+internal actual fun Float.multiplatformToString(): String = toString()