Eng:() * () (block)

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() * ()
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))

• Velocity

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*10³ 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

• () + ()
• () - ()
• () / ()