# Difference between revisions of "ApCoCoA-1:BB.ASneighbors"

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Computes the list of across-the-street neighbors in the border of the order ideal OO. The input is a list OO of terms that specify an order ideal. The output is a list of quadruples <formula>[i,j,k,l]</formula> such that <formula>x_k * b_i = x_l * b_j</formula>. | Computes the list of across-the-street neighbors in the border of the order ideal OO. The input is a list OO of terms that specify an order ideal. The output is a list of quadruples <formula>[i,j,k,l]</formula> such that <formula>x_k * b_i = x_l * b_j</formula>. | ||

<example> | <example> | ||

+ | Use Q[x,y,z]; | ||

$borderbasis.ASneighbors([1,x]); | $borderbasis.ASneighbors([1,x]); | ||

[[1, 2, 2, 3], [3, 4, 2, 3], [3, 5, 1, 3], [4, 5, 1, 2]] | [[1, 2, 2, 3], [3, 4, 2, 3], [3, 5, 1, 3], [4, 5, 1, 2]] |

## Revision as of 22:14, 7 November 2007

## borderbasis.ASneighbors

list of across-the-street neighbors

### Syntax

$borderbasis.ASneighbors(OO:LIST):LIST

### Description

Computes the list of across-the-street neighbors in the border of the order ideal OO. The input is a list OO of terms that specify an order ideal. The output is a list of quadruples <formula>[i,j,k,l]</formula> such that <formula>x_k * b_i = x_l * b_j</formula>.

#### Example

Use Q[x,y,z]; $borderbasis.ASneighbors([1,x]); [[1, 2, 2, 3], [3, 4, 2, 3], [3, 5, 1, 3], [4, 5, 1, 2]] -------------------------------