### 2.12.1 Evaluate an expression : `eval`

`eval` is used to evaluate an expression. Since
`Xcas` always evaluate expressions entered in the commandline,
`eval` is mainly used
to evaluate a sub-expression in the equation writer.

Input :

`a:=2`

Output :

`2`

Input :

`eval(2+3*a)`

or

`2+3*a`

Output :

`8`