# Studies of Euler diagrams/gapspots/hard and soft

Some gapspots can not be avoided, while others are a design choice. They could be called hard and soft. On this page functions with hard gapspots are marked with ⚒.

## between different bundles ⚒

There is no way to avoid gapspots between different bundles. The simplest examples are:

• two sets in an otherwise empty set   (sarina: H and F in G)
• one set in an otherwise empty intersection   (cm1: C in A and B)
bazinga gapspots

sarina

futare

geteso

## XOR ⚒

Functions in the same box are complements. Those on the left (right) are true in cells with even (odd) digit sum.

3-ary

One could choose an Euler diagram with 7 cells (compare bunese), which would remove one of the gapspots. But that would be a random choice, which should be avoided.

selera

pelele

## vanatu ⚒

This is a XOR including an OR:    ${\displaystyle A~\oplus ~(B\lor C)~\oplus ~D}$           It is a gap variant of bar and a filtrate of tomute.

3-ary

## bunese (7 of 8 cells)

Below are three possible Euler diagrams of the same Boolean function. It is ${\displaystyle \neg (A\land B\land C)}$ in logic, and ${\displaystyle A\cap B\cap C=\emptyset }$ in set theory.

variants
• left:   The false cell is shown as a gapspot.
• middle:   An intersection of three borders is shown instead.
• right:   With three straight lines the plane can be partitioned in seven areas.

## foravo (hexagon)

variants

This function can reasonably be shown with two or no gapspots. The latter means, that the three borders intersect in one point.
This point could be enlarged into gapspot 0 or 7. But that would be a random choice, which should be avoided.

both gapspots

gapspot 0

no gapspots

gapspot 7

grid

potula

kinide

gilipi

## kagusi (2×4) ⚒

If the gapspots were true, the red circle would vanish.

graph, Euler diagram

## 1- or 2-dimensional

Euler diagrams can be drawn with gapspots in a higher dimension, or without in a lower. Generally one should prefer the lowest possible dimension. But it is reasonable to demand from an Euler diagram, that the set borders be contiguous - which a circle in one dimension (a 0-sphere) is not. So in this case, one might prefer the 2D diagrams, and consider the gapspots necessary. (The disconnected left and right parts are easier seen in this version of the 1D diagram on the right.)

gapspots bundles 3-2-2-1   cm2 gapspots 5×4   gufaro
Distance between cells 37 and 32:   2 above, 4 below Distance between cells 10 and 24:   2 above, 6 below

## piferi

Like example putuki, but with spot 0 as gapspot.   (Compare logota, another octagon.)

matrix and circular graph
3×3 graph with gapspot
1-dimensional graph and Euler diagram closed to a circle

kabine
kasete