# Module kmath-ast Abstract syntax tree expression representation and related optimizations. - [expression-language](src/commonMain/kotlin/space/kscience/kmath/ast/parser.kt) : Expression language and its parser - [mst-jvm-codegen](src/jvmMain/kotlin/space/kscience/kmath/asm/asm.kt) : Dynamic MST to JVM bytecode compiler - [mst-js-codegen](src/jsMain/kotlin/space/kscience/kmath/estree/estree.kt) : Dynamic MST to JS compiler - [rendering](src/commonMain/kotlin/space/kscience/kmath/ast/rendering/MathRenderer.kt) : Extendable MST rendering ## Artifact: The Maven coordinates of this project are `space.kscience:kmath-ast:0.3.0-dev-7`. **Gradle:** ```gradle repositories { maven { url 'https://repo.kotlin.link' } mavenCentral() } dependencies { implementation 'space.kscience:kmath-ast:0.3.0-dev-7' } ``` **Gradle Kotlin DSL:** ```kotlin repositories { maven("https://repo.kotlin.link") mavenCentral() } dependencies { implementation("space.kscience:kmath-ast:0.3.0-dev-7") } ``` ## Dynamic expression code generation ### On JVM `kmath-ast` JVM module supports runtime code generation to eliminate overhead of tree traversal. Code generator builds a special implementation of `Expression` with implemented `invoke` function. For example, the following builder: ```kotlin MstField { bindSymbol("x") + 2 }.compileToExpression(DoubleField) ``` ... leads to generation of bytecode, which can be decompiled to the following Java class: ```java package space.kscience.kmath.asm.generated; import java.util.Map; import kotlin.jvm.functions.Function2; import space.kscience.kmath.asm.internal.MapIntrinsics; import space.kscience.kmath.expressions.Expression; import space.kscience.kmath.expressions.Symbol; public final class AsmCompiledExpression_45045_0 implements Expression { private final Object[] constants; public final Double invoke(Map arguments) { return (Double)((Function2)this.constants[0]).invoke((Double)MapIntrinsics.getOrFail(arguments, "x"), 2); } public AsmCompiledExpression_45045_0(Object[] constants) { this.constants = constants; } } ``` #### Known issues - The same classes may be generated and loaded twice, so it is recommended to cache compiled expressions to avoid class loading overhead. - This API is not supported by non-dynamic JVM implementations (like TeaVM and GraalVM) because of using class loaders. ### On JS A similar feature is also available on JS. ```kotlin MstField { bindSymbol("x") + 2 }.compileToExpression(DoubleField) ``` The code above returns expression implemented with such a JS function: ```js var executable = function (constants, arguments) { return constants[1](constants[0](arguments, "x"), 2); }; ``` JS also supports very experimental expression optimization with [WebAssembly](https://webassembly.org/) IR generation. Currently, only expressions inside `DoubleField` and `IntRing` are supported. ```kotlin import space.kscience.kmath.wasm.* MstField { bindSymbol("x") + 2 }.compileToExpression(DoubleField) ``` An example of emitted Wasm IR in the form of WAT: ```lisp (func $executable (param $0 f64) (result f64) (f64.add (local.get $0) (f64.const 2) ) ) ``` #### Known issues - ESTree expression compilation uses `eval` which can be unavailable in several environments. - WebAssembly isn't supported by old versions of browsers (see https://webassembly.org/roadmap/). ## Rendering expressions kmath-ast also includes an extensible engine to display expressions in LaTeX or MathML syntax. Example usage: ```kotlin import space.kscience.kmath.ast.* import space.kscience.kmath.ast.rendering.* public fun main() { val mst = "exp(sqrt(x))-asin(2*x)/(2e10+x^3)/(-12)".parseMath() val syntax = FeaturedMathRendererWithPostProcess.Default.render(mst) val latex = LatexSyntaxRenderer.renderWithStringBuilder(syntax) println("LaTeX:") println(latex) println() val mathML = MathMLSyntaxRenderer.renderWithStringBuilder(syntax) println("MathML:") println(mathML) } ``` Result LaTeX: ![](http://chart.googleapis.com/chart?cht=tx&chl=e%5E%7B%5Csqrt%7Bx%7D%7D-%5Cfrac%7B%5Cfrac%7B%5Coperatorname%7Bsin%7D%5E%7B-1%7D%5C,%5Cleft(2%5C,x%5Cright)%7D%7B2%5Ctimes10%5E%7B10%7D%2Bx%5E%7B3%7D%7D%7D%7B-12%7D) Result MathML (embedding MathML is not allowed by GitHub Markdown): ```html ex-sin-12x2×1010+x3-12 ``` It is also possible to create custom algorithms of render, and even add support of other markup languages (see API reference).