## Data and Expression

There are constants (provided by the host application), global and local variables, scalar variables (data type `number_t`), numeric arrays (element data type `number_t`), and strings (element data type `int8_t`). Global variables are stored on the heap, wheras local variables are stored on the data stack.

Scalar and string global variables can be explicitly defined and allocated using the `var` statement or by assigning a value. Not allocated variables may not be used in expressions. Array variables must be defined by using the `var` statements as well as local variables by using the `var*` statement. 

Expressions with infix notation are compiled into stack operations with post-fix operations, preserving operator bindings.

| Statement | Description |
|:--|:--|
| `var a,b(20),c$,d$(10)` | Definition and allocation of scalar (a), array (b), string (c), and string with length (d) variables.  |
| `var* a,b,c` | Definition of local variables (on stack)  |
| `const a=n,b=n,c=n` | Definition of constant values (on heap, but read-only, only numbers or characters *n* can be assigned)  |
| `x=ε` | Assignment of value to variable *x* (with allocation if not already defined) |

### Operators

| Operators | Description |
|:--|:--|
| `+ - * / mod` | Arithmetic infix operations |
| `< > <= >=` | Relational infix operations |
| `and or not` | Logical and Boolean infix and prefix operations |
| `$var `|  Address of variable (postive: heap: neagtive: data stack) |
| `var$` | String variable |
| `x(i)` | Array selector (first index is 1) |