Reorganizing paths

common/src/module/expreval.mjs

@@ -0,0 +1,114 @@
+/**
+ *  LogarithmPlotter - 2D plotter software to make BODE plots, sequences and distribution functions.
+ *  Copyright (C) 2021-2024  Ad5001
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import { Module } from "./common.mjs"
+import { Parser } from "../lib/expr-eval/parser.mjs"
+
+const evalVariables = {
+    // Variables not provided by expr-eval.js, needs to be provided manually
+    "pi": Math.PI,
+    "PI": Math.PI,
+    "π": Math.PI,
+    "inf": Infinity,
+    "infinity": Infinity,
+    "Infinity": Infinity,
+    "∞": Infinity,
+    "e": Math.E,
+    "E": Math.E,
+    "true": true,
+    "false": false
+}
+
+class ExprParserAPI extends Module {
+    constructor() {
+        super("ExprParser")
+        this.currentVars = {}
+        this._parser = new Parser()
+
+        this._parser.consts = Object.assign({}, this._parser.consts, evalVariables)
+
+        this._parser.functions.integral = this.integral.bind(this)
+        this._parser.functions.derivative = this.derivative.bind(this)
+    }
+
+    /**
+     * Parses arguments for a function, returns the corresponding JS function if it exists.
+     * Throws either usage error otherwise.
+     * @param {array} args - Arguments of the function, either [ ExecutableObject ] or [ string, variable ].
+     * @param {string} usage1 - Usage for executable object.
+     * @param {string} usage2 - Usage for string function.
+     * @return {function} JS function to call.
+     */
+    parseArgumentsForFunction(args, usage1, usage2) {
+        let f, variable
+        if(args.length === 1) {
+            // Parse object
+            f = args[0]
+            if(typeof f !== "object" || !f.execute)
+                throw EvalError(qsTranslate("usage", "Usage:\n%1").arg(usage1))
+            let target = f
+            f = (x) => target.execute(x)
+        } else if(args.length === 2) {
+            // Parse variable
+            [f, variable] = args
+            if(typeof f !== "string" || typeof variable !== "string")
+                throw EvalError(qsTranslate("usage", "Usage:\n%1").arg(usage2))
+            f = this._parser.parse(f).toJSFunction(variable, this.currentVars)
+        } else
+            throw EvalError(qsTranslate("usage", "Usage:\n%1\n%2").arg(usage1).arg(usage2))
+        return f
+    }
+
+    /**
+     * @param {string} expression - Expression to parse
+     * @returns {ExprEvalExpression}
+     */
+    parse(expression) {
+        return this._parser.parse(expression)
+    }
+
+    integral(a, b, ...args) {
+        let usage1 = qsTranslate("usage", "integral(<from: number>, <to: number>, <f: ExecutableObject>)")
+        let usage2 = qsTranslate("usage", "integral(<from: number>, <to: number>, <f: string>, <variable: string>)")
+        let f = this.parseArgumentsForFunction(args, usage1, usage2)
+        if(a == null || b == null)
+            throw EvalError(qsTranslate("usage", "Usage:\n%1\n%2").arg(usage1).arg(usage2))
+
+        // https://en.wikipedia.org/wiki/Simpson%27s_rule
+        // Simpler, faster than tokenizing the expression
+        return (b - a) / 6 * (f(a) + 4 * f((a + b) / 2) + f(b))
+    }
+
+    derivative(...args) {
+        let usage1 = qsTranslate("usage", "derivative(<f: ExecutableObject>, <x: number>)")
+        let usage2 = qsTranslate("usage", "derivative(<f: string>, <variable: string>, <x: number>)")
+        let x = args.pop()
+        let f = this.parseArgumentsForFunction(args, usage1, usage2)
+        if(x == null)
+            throw EvalError(qsTranslate("usage", "Usage:\n%1\n%2").arg(usage1).arg(usage2))
+
+        let derivative_precision = x / 10
+        return (f(x + derivative_precision / 2) - f(x - derivative_precision / 2)) / derivative_precision
+    }
+}
+
+/** @type {ExprParserAPI} */
+Modules.ExprParser = Modules.ExprParser || new ExprParserAPI()
+
+export default Modules.ExprParser
+