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Primitive Types

BAML supports five primitive types for basic data representation.

Overview​

TypeDescriptionExample Values
stringText data"hello", "world"
intInteger numbers1, -5, 100
floatFloating point numbers3.14, -0.5, 1.0
boolBoolean valuestrue, false
nullAbsence of valuenull

String​

BAML supports three string formats:

Quoted Strings (Inline)​

Standard double-quoted strings for simple values:

"Hello World"
"\n"  // escape sequences supported

Unquoted Strings​

Simple strings without quotes (for configuration values):

Hello World
warning

Unquoted strings cannot contain: ", ', @, {}, #, (), [], ,, or newlines.

Block Strings​

Multi-line strings with Jinja templating support:

#"
Hello
World
"#

Block strings are automatically dedented and support Jinja syntax:

template_string Greeting(name: string) #"
  Hello {{ name }}!
"#

To include "# in a block string, use more # characters:

###"
  #"Hello"#
"###

Int and Float​

Numerical types for integer and decimal values.

function DescribeCircle(radius: int | float, pi: float?) -> string {
    client "openai/gpt-4o-mini"
    prompt #"
        Describe a circle with radius {{ radius }}.
        Use pi as {{ pi or 3.14159 }}.
    "#
}

test IntRadius {
    functions [DescribeCircle]
    args { radius 5 }  // cast to int
}

test FloatRadius {
    functions [DescribeCircle]
    args {
        radius 5.0   // cast to float
        pi 3.14
    }
}
tip

BAML supports implicit casting from int to float. Use 0.0 instead of 0 to explicitly specify a float.

Bool​

Boolean type for true/false values.

function CreateStory(long: bool) -> string {
    client "openai/gpt-4o-mini"
    prompt #"
        Write a story that is {{ "10 paragraphs" if long else "1 paragraph" }} long.
    "#
}

test LongStory {
    functions [CreateStory]
    args { long true }
}

test ShortStory {
    functions [CreateStory]
    args { long false }
}

Null​

Represents absence of a value. Typically used with optional types (Type?).

See Also​