Add type definitions for math-expression-evaluator (#43009)

Co-authored-by: Adam Zerella <adamzerella@users.noreply.github.com>

types/math-expression-evaluator/index.d.ts

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+// Type definitions for math-expression-evaluator 1.2
+// Project: https://github.com/bugwheels94/math-expression-evaluator
+// Definitions by:  Adam Zerella <https://github.com/adamzerella>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+interface Token {
+    token: string;
+    type: number;
+    value?: string|((a: number, b?: number) => number);
+    show: string;
+    preced?: number;
+}
+
+declare class Mexp {
+    static lex(inp: string, tokens?: Token[]): Mexp;
+    formulaEval(): Mexp;
+    toPostfix(): Mexp;
+    postfixEval(pair?: object): number|string;
+    static eval(exp: string, tokens?: Token[], pair?: object): string;
+    static eval(exp: string, mexp?: object): string;
+    static addToken(tokens: Token[]): void;
+}
+
+export = Mexp;

types/math-expression-evaluator/math-expression-evaluator-tests.ts

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+import Mexp = require("math-expression-evaluator");
+
+Mexp.eval("5*.8");
+Mexp.eval("5*.8", { mexp: 5 });
+Mexp.eval("mexp(3)", [{
+    type: 0,
+    show: "mexp(\",value:function(a){return 5*a;}",
+    preced: 11,
+    token: "mexp"
+}]);
+Mexp.eval("mexp(3)", [{
+    type: 0,
+    token: "inverse",
+    show: "inverse",
+    value: (a => 1 / a)
+}]);
+
+Mexp.addToken([{
+    type: 3,
+    token: "git",
+    show: "git",
+    value: "git"
+}]);
+Mexp.eval("mexp*3", { mexp: 5 });
+
+Mexp.addToken([{
+    type: 0,
+    show: "mexp",
+    value: (a => 5 * a),
+    preced: 11,
+    token: "mexp"
+}]);
+Mexp.lex("mexp3").toPostfix().postfixEval();
+
+Mexp.lex('mexp3').toPostfix();
+Mexp.lex('mexp3').toPostfix().formulaEval();

types/math-expression-evaluator/tsconfig.json

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+{
+    "compilerOptions": {
+      "module": "commonjs",
+      "lib": [
+        "es6"
+      ],
+      "noImplicitAny": true,
+      "noImplicitThis": true,
+      "strictNullChecks": true,
+      "strictFunctionTypes": true,
+      "baseUrl": "../",
+      "typeRoots": [
+        "../"
+      ],
+      "types": [
+
+      ],
+      "noEmit": true,
+      "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+      "index.d.ts",
+      "math-expression-evaluator-tests.ts"
+    ]
+}

types/math-expression-evaluator/tslint.json

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+{
+    "extends": "dtslint/dt.json"
+}