Added a section on implicit multiplication

docs/expressions.md

@@ -303,7 +303,7 @@ Operators                         | Description
 `^`, `.^`                         | Exponentiation
 `+`, `-`                          | Unary plus, unary minus
 `x unit`                          | Unit
-`*`, `/`, `.*`, `./`, `%`, `mod`  | Multiply, divide, modulus
+`*`, `/`, `.*`, `./`, `%`, `mod`  | Multiply, divide, modulus, implicit multiply
 `+`, `-`                          | Add, subtract
 `:`                               | Range
 `==`, `!=`, `<`, `>`, `<=`, `>=`  | Comparison
@@ -665,6 +665,32 @@ math.eval('a=3; b=4; a + b \n a * b');  // Array, [7, 12]
 ```
 
 
+### Implicit multiplication
+
+The expression parser supports implicit multiplication. Implicit multiplication
+has the same precedence as explicit multiplications and divisions, so `3/4 mm`
+is evaluated as `(3 / 4) * mm`. Here some examples:
+
+Expression      | Evaluated as:
+--------------- | ----------------------
+(3 + 2) b       | (3 + 2) * b
+3 / 4 mm        | (3 / 4) * mm
+(1 + 2) (4 - 2) | (1 + 2) * (4 - 2)
+sqrt(2)(4 + 1)  | sqrt(2) * (4 + 1)
+A[2, 3]         | A[2, 3]   # get subset
+(A)[2, 3]       | (A) * [2, 3]
+[2, 3][1, 3]    | [2, 3] * [1, 3]
+
+Implicit multiplication can be tricky as there is ambiguity on how an expression
+is evaluated. Use it carefully.
+
+```js
+math.eval('(1 + 2)(4 - 2)');  // Number, 6
+math.eval('3/4 mm');          // Unit, 0.75 mm
+math.eval('2 + 3i');          // Complex, 2 + 3i
+```
+
+
 ### Comments
 
 Comments can be added to explain or describe calculations in text. A comment

examples/complex_numbers.js

@@ -38,7 +38,7 @@ console.log();
 console.log('perform operations');
 print(math.add(a, b));          // 8 - 4i
 print(math.multiply(a, b));     // 36 - 26i
-print(math.sin(a));             // -9.6541 + 2.8417i
+print(math.sin(a));             // -9.6541254768548 + 2.8416922956064i
 
 // some operations will return a complex number depending on the arguments
 print(math.sqrt(4));           // 2