# CoCoA:In

From ApCoCoAWiki

## In

create a list satisfying given conditions

### Description

In the first form, E is an arbitrary CoCoA expression and B is a

boolean expression, both of which are functions of the variable

X. Write E(X) for E and B(X) for B. The first listed command then returns the list of all E(X) such that X is in the list L and B(X) evaluates to TRUE.

#### Example

[[X^2,X^3] | X In [-2,-1,0,1,2] And X <> 0]; [[4, -8], [1, -1], [1, 1], [4, 8]] ------------------------------- [X In [1,2] >< [2,3,4] | X[1]+X[2]=4]; [[1, 3], [2, 2]] -------------------------------

(Note: the <formula>><</formula> operator is used to form Cartesian products; it is not
the same as the *not equal* operator, <formula><></formula>.)

The second form of the command is the same as the first with E = X.

#### Example

[X In [1,2,3] | X > 1]; [2, 3] -------------------------------

The third form is the same as the first with B = TRUE.

#### Example

[X^2 | X In [1,2,3]]; [1, 4, 9] -------------------------------

### Syntax

[E:OBJECT | X In L:LIST And B:BOOL]:LIST [X In L:LIST | B:BOOL]:LIST [E:OBJECT | X In L] where X is a variable identifier which may occur in B or E.

<type>list</type>