Unit

Unit (Function)

Format

unit ( vector )

returns an array.

Description

Returns the same vector scaled to length one — a direction with the distance taken out of it. Every element of the vector held in the array is divided by the length of the vector, which is what norm gives.

The answer keeps the shape of the vector it was given, and every element of it is a decimal number.

This is what a program wants whenever something should move at a set speed however far away its target is: unit of the gap between two points is a step of exactly one toward the target, so multiplying it by a speed moves that far and no further.

unit of a vector with no length — one whose elements are all zero — is an error, because there is no direction to give back. Where that can happen, check the length with norm first, or catch the error with Try.

Example

u = unit({3,4})
print u[0,0]; ","; u[0,1]
print norm(u)

# move ball_x, ball_y three pixels toward target_x, target_y
gap = {target_x - ball_x, target_y - ball_y}
if norm(gap) > 0 then
   step = unit(gap)
   ball_x = ball_x + step[0,0] * 3
   ball_y = ball_y + step[0,1] * 3
end if

will print

0.6,0.8
1.0

Errors

Error	Cause
136	The value passed is not an array.
139	An element of the vector has never been given a value.
140	The vector has no length, so it has no direction.

See Also

Arrays, Cross, Dot, Norm, Try, Vector Operators

History

2.2	New To Version