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The () Mod () block ("mod" is short for "modulo") is an Operators block and a Reporter block. The block reports the remainder of the division when the first value is divided by the second. For example, when 10 is put in the first input and 3 in the second, the block will report 1; 10 divided by 3 gives a remainder of 1.
Negative numbers behave a little differently, because a remainder must always be positive. -10 mod 3 equals 2, not -1, because you have to multiply 3 by -4 to have any remainder at all.
If a project is doing divisibility tests, the () Mod () block can be of use.
Some common uses for the () Mod () block:
- Checking if two numbers divide without a remainder
if <((a) mod (b)) = > then say [a is divisible by b] else say [a is not divisible by b] end
- Checking if a number is a whole number
if <((a) mod (1)) = > then say [a is a whole number] else say [a is not a whole number] end
- Checking if numbers are odd or even
if <((a) mod (2)) = > then say [a is an even number] else if <((a) mod (1)) = > then say [a is an odd number] else say [a is not an integer] end end
- Repeatedly iterating through a list:
when gf clicked set [x v] to  forever change [x v] by (1) say (item (x) of [list v]) set [x v] to ((x) mod (length of [list v]))
- Reusing background-sprites when scrolling
when gf clicked forever set x to (((x position) + (240)) mod (480))
- Main article: List of Block Workarounds
If only positive numbers are wanted, the block can be replicated with the following code (the variable remainder is the reported value):
if <(round ((a) / (b))) > ((a) / (b))> then set [remainder v] to ((a) - ((round (((a) / (b)) - (0.5))) * (b))) else set [remainder v] to ((a) - ((round ((a) / (b))) * (b))) end
Negative values are rarely used in the () Mod () block, although it is possible. The output given when a negative value is in the first insert and a positive value is in the second is the positive value, so if the negative value is wanted, you must subtract the number in the second insert from the remainder, as so:
if <(a) < (0)> then if <(b) > (0)> then set [remainder v] to (((a) mod (b)) - (b)) else set [remainder v] to ((a) mod (b)) end else set [remainder v] to ((a) mod (b))