Merge pull request #38 from quintindunn/dva-t-graphing-mathjs-port

Remove expr-eval and substitute with math.js

static/graphs/js/dva_graphs/condition_processing.js

@@ -1,12 +1,10 @@
-import { Parser } from "/static/node_modules/expr-eval/dist/index.mjs";
-
 // What operators to check for in the piecewise function (pwf)
 const OPERATORS = ['<', '<=', '>', '>='];
 
 // Generate the regex pattern given the operators.
 const PATTERN = new RegExp('(' + OPERATORS.map(operator => operator.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&')).join('|') + ')');
 
-// Splits the condition, so it can be evaluated piece by piece (10<x<15 -> ["10<x", "x<15"]
+// Splits the condition, so it can be evaluated piece by piece (10<t<15 -> ["10<t", "t<15"]
 function splitExpr(expr) {
     // Split the expression using the regex pattern
     const result = expr.split(PATTERN);
@@ -17,12 +15,12 @@ function splitExpr(expr) {
         comparisons.push(result.slice(i, i + 3));
     }
 
-    // append/prepend `x` to the conditions, so it can be evaluated one by one. prepend if first char is an operator, append if first character is a number.
+    // append/prepend `t` to the conditions, so it can be evaluated one by one. prepend if first char is an operator, append if first character is a number.
     return comparisons.map(comparison => {
         if (OPERATORS.includes(comparison[1])) {
             return comparison.join('');
         } else if (OPERATORS.includes(comparison[0])) {
-            return 'x' + comparison.join('');
+            return 't' + comparison.join('');
         }
     });
 }
@@ -33,8 +31,8 @@ export function evalExpr(expr, x) {
 
     // Loop through the expressions and evaluate each one, if any returns false, return false, otherwise return true.
     for (const subExpr of expressions) {
-        const evalExpr = subExpr.replace('x', x.toString());
-        if (Parser.evaluate(evalExpr, { x: x }) === false) {
+        const evalExpr = subExpr.replace('t', x.toString());
+        if (math.evaluate([`t=` + x, evalExpr])[1] === false) {
             return false; // Condition failed.
         }
     }

static/graphs/js/dva_graphs/dva_graphs.js

@@ -1,9 +1,7 @@
 import * as d3 from "https://cdn.jsdelivr.net/npm/d3@7/+esm";
-import { MathFunction, PiecewiseFunction, preParseExpression } from "/static/graphs/js/dva_graphs/function.js";
+import { MathFunction, PiecewiseFunction } from "/static/graphs/js/dva_graphs/function.js";
 import { evalExpr } from "./condition_processing.js";
 
-import { Parser } from "/static/node_modules/expr-eval/dist/index.mjs";
-
 // Declare the chart dimensions and margins.
 const equation_error_div = document.getElementById("error-div")
 
@@ -102,7 +100,7 @@ function checkInput(expr, is_condition=false) {
     if (is_condition) {
         // Check if it is valid
         try {
-            evalExpr(expr, 0); // 0 As placeholder, if this throws an error it is incorrect.
+            math.evaluate(['t=0', expr]);
         } catch (err) {
             return CODES.ERROR;
         }
@@ -116,7 +114,11 @@ function checkInput(expr, is_condition=false) {
     let parsed;
 
     try {
-        parsed = Parser.parse(expr).toJSFunction("x"); // Return a function that takes `x` to evaluate the expr.
+        // Test expression to make sure it is valid.
+        math.evaluate(["t=" + 0, expr])
+
+        // Return a function that takes `x` to evaluate the expr.
+        parsed = (x) => {return math.evaluate(["t=" + x, expr])[1]};
     }
     catch(err) {
         return parsed ?? CODES.ERROR; // expression is invalid
@@ -166,11 +168,10 @@ function graph_function() {
 
         // Redundancy check.
         if (inp_name === "equation" || inp_name === "condition") {
-             // preparse the expression to allow implicit multiplication i.e. 5x -> 5*x.
-            let preparsed = preParseExpression(inp.value, ['x']);
+            const expr = inp.value.replaceAll("x", "t") // Use `t` instead of `x` as mathjs throws an error with 0x
 
             // Validate the input, if it's true returns a function where you pass in the `x` value.
-            let jsFunc_eq = checkInput(preparsed, inp_name === "condition");
+            let jsFunc_eq = checkInput(expr, inp_name === "condition");
 
             // Blank, skip the expr.
             if (jsFunc_eq === 0) continue;

static/graphs/js/dva_graphs/function.js

@@ -79,42 +79,4 @@ export class PiecewiseFunction {
 
         return pointsArr;
     }
-}
-
-
-export function preParseExpression(expressionString, variables) {
-    // CREDIT: https://github.com/silentmatt/expr-eval/issues/1#issuecomment-42589068
-    variables = variables.join('');
-
-    // Build an object with replacement rules. (The order matters!)
-    let re = {};
-    // Turns 'x^xy' into 'x^(x*y)'.
-    re.parenthesizeVariables = {
-      expr : new RegExp('([0-9' + variables + ']+)([' + variables + ']+)'),
-      repl : '($1*$2)',
-    };
-    // Turns '2(3+y)' into '2*(3+y)'.
-    re.parenthesisCoefficients = {
-      expr : /(\d+)([(])/i,
-      repl : '$1*$2'
-    };
-    // Turns '(x^xy)(x-y)' into '(x^xy)*(x-y)'.
-    re.parenthesisMultiplication = {
-      expr : /([)])([(])/,
-      repl : '$1*$2',
-    };
-    // Turns '2sin' into '2*sin'.
-    re.functionCoefficients = {
-      expr : /(\d+)([a-z]+)/i,
-      repl : '$1*$2',
-    };
-
-    // Apply the replacement rules.
-    for (let i in re) {
-      while (expressionString.replace(re[i].expr, re[i].repl) !== expressionString) {
-        expressionString = expressionString.replace(re[i].expr, re[i].repl);
-      }
-    }
-
-    return expressionString;
-  }
+}

static/package.json

@@ -19,6 +19,6 @@
   "homepage": "https://github.com/quintindunn/APhysicsWeb#readme",
   "dependencies": {
     "d3": "^7.8.5",
-    "expr-eval": "^2.0.2"
+    "mathjs": "^11.11.2"
   }
 }