fix: 2e != e2

This is a supplement to the last commit.

src/compiler/Compiler.ts

@@ -143,7 +143,7 @@ export default class Compiler {
                     } else {
                         this.pushVariable(symbol);
 
-                        if(Is.variable(symbol) && Is.number(this.raw[i + 1], this.isProgrammingMode)) {
+                        if(Is.pureNumber(this.raw[i + 1])) {
                             this.pushOperator(Operator.MUL);
                         }
                     }

src/compiler/Is.ts

@@ -11,6 +11,13 @@ export default class Is {
             return number.indexOf(symbol) > -1;
         }
     }
+
+    public static pureNumber(symbol: string): boolean {
+        const number = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "0", "."];
+        if(!symbol) return false;
+
+        return number.indexOf(symbol) > -1;
+    }
 
     public static operator(symbol: string): boolean {
         const operator = [

src/test/compiler.test.ts

@@ -138,17 +138,20 @@ describe("Compiler tests", () => {
         const f9 = "( 2 e ) \\pi";
         expect(calculate(f9)).toBe("17.07946844534713");
 
-        const f10 = "( e \\pi ) 2";
-        expect(calculate(f10)).toBe("17.07946844534714");
+        const f10 = "( e 2 ) \\pi";
+        expect(calculate(f10)).toBe("17.07946844534713");
 
-        const f11 = "2 ^2 e";
-        expect(calculate(f11)).toBe("10.87312731383618");
+        const f11 = "( e \\pi ) 2";
+        expect(calculate(f11)).toBe("17.07946844534714");
 
-        const f12 = "3 1 b";
-        expect(calculate(f12, variables)).toBe("403");
+        const f12 = "2 ^2 e";
+        expect(calculate(f12)).toBe("10.87312731383618");
 
-        const f13 = "b 3 1";
+        const f13 = "3 1 b";
         expect(calculate(f13, variables)).toBe("403");
+
+        const f14 = "b 3 1";
+        expect(calculate(f14, variables)).toBe("403");
     });
 
     test("Integrated Calculations", () => {