~ ( x y epsilon -- ? )
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round-to-step ( x step -- y )

Vocabulary
math.functions

Inputs

x	a real
y	a real
epsilon	a real

Outputs

?

a boolean

Word description
Tests if x and y are approximately equal to each other. There are three possible comparison tests, chosen based on the sign of epsilon:

•	epsilon is zero: exact comparison.
•	epsilon is positive: absolute distance test.
•	epsilon is negative: relative distance test.

Definition

USING: combinators kernel math ;

IN: math.functions

: ~ ( x y epsilon -- ? )
    {
        { [ dup zero? ] [ drop number= ] }
        { [ dup 0 < ] [ neg ~rel ] }
        [ ~abs ]
    } cond ;