From Test-Scratch-Wiki

() * () | |

Category |
Operators |

Type |
Reporter |

The **() * ()** block is an Operators block and a Reporter block. The block multiplies the two values and reports the result. In Snap!, it will be shown as () × ().

The numbers can be typed directly into the block, or Reporter blocks can be used instead.

This block can be stacked inside itself - this can be used to fit more numbers in or calculate exponents.

## Example Uses

In many projects, numbers must be multiplied; this block will do the job.

Some common uses for the () * () block:

- Scripts in calculator simulations

set [result v] to ((a) * (b))

- Multiplying lists of numbers

set [result v] to (1) set [item v] to (1) repeat (length of [numbers v]) set [result v] to ((result) * (item (item) of [numbers v])) change [item v] by (1) end

- Math formulas

([sqrt v] of ((((y1) - (y2)) * ((y1) - (y2))) + (((x1) - (x2)) * ((x1) - (x2))))) //Pythagorean Theorem

- Score multipliers

set [score v] to ((score) * (2))

when gf clicked set [velocity v] to [0] forever if <key [space v] pressed?> then change [velocity v] by (2) set [velocity v] to ((velocity) * (0.87)) //simulates friction slowdown

- 3D Projects

## Scientific Notation

In Scratch 1.4 and previous versions, it sometimes converts very large numbers into scientific notation to save space. Scientific notation is simply the number in the form a*10^{b}. These can be converted to a normal number by performing any mathematical function on it, such as adding. So if a variable named "number" has a value of 3*10^{3} and you want to display it as a normal number, you can change it by:

((number) + (0))

It will then report "3000".

## Workaround

*Main article: List of Block Workarounds*

With natural numbers, this block can be replicated with the following code, assuming a is the first number and b is the second number:

set [product v] to [0] repeat (b) change [product v] by (a)

The following code works for all cases (with the conditional). It divides by the reciprocal, the equivalent of multiplying.

if <(b) = (0)> then set [product v] to [0] else set [product v] to ((a) / ((1) / (b))) end

The following code accepts negative numbers with decimals:

delete (all v) of [num1 numbers v] //setup delete (all v) of [num2 numbers v] delete (all v) of [product digits v] set [product v] to [0] set [dec pos 1 v] to [0] set [dec pos 2 v] to [0] ask [num1] and wait if <(answer) < [0]> then set [count v] to [1] set [no 1 negative v] to [y] else set [count v] to [0] set [no 1 negative v] to [n] end repeat (length of (answer)) change [count v] by (1) if <not <(letter (count) of (answer)) = [.]>> then add (letter (count) of (answer)) to [num1 numbers v] else set [dec pos 1 v] to ((length of (answer)) - (count)) end end ask [num2] and wait if <(answer) < [0]> then set [count v] to [1] set [no 2 negative v] to [y] else set [count v] to [0] set [no 2 negative v] to [n] end repeat (length of (answer)) change [count v] by (1) if <not <(letter (count) of (answer)) = [.]>> then add (letter (count) of (answer)) to [num2 numbers v] else set [dec pos 2 v] to ((length of (answer)) - (count)) end end set [num1 v] to (num1 numbers) set [num2 v] to (num2 numbers) repeat (num1) //start change [product v] by (num2) end set [decimal position v] to ((dec pos 1) + (dec pos 2)) set [count v] to [0] repeat (length of (product)) change [count v] by (1) add (letter (count) of (product)) to [product digits v] end if <not <(decimal position) = [0]>> then insert [.] at ((length of [product digits v]) - ((decimal position) - (1))) of [product digits v] end if <<<(no 1 negative) = [y]> or <(no 2 negative) = [y]>> and <not <<(no 1 negative) = [y]> and <(no 2 negative) = [y]>>>> then insert [-] at (1 v) of [product digits v] end set [product v] to (product digits)

## See Also

() + ()
• () of ()More blocks... |