Data Types

ENG v0.1.0 has six runtime value categories.

Number

Numbers are stored as f64, so integer-looking and fractional values use the same runtime type:

Let whole be 5.
Let fraction be 2.5.
Print whole plus fraction.

String

Let name be "ENG".
Print name.

Strings can be concatenated with plus.

Boolean

The literals are:

true
false

Example:

Let enabled be true.
Print enabled.

List

Lists are created with:

Make a list called numbers.

Values can then be added with Add.

Function

A function definition creates a callable runtime value:

Define a function called square that takes x and returns x multiplied by x.

Nothing

nothing is the runtime value used when a function has no explicit return expression and for missing variable loads in the current VM implementation.

Truthiness

Conditions use runtime truthiness:

• false is false.
• nothing is false.
• Number 0 is false; other numbers are true.
• An empty string is false; non-empty strings are true.
• An empty list is false; non-empty lists are true.
• Functions are true.

This matters for If and While.