Special Methods

Among the 256 method codes, the first 16 (0x0 to 0xF) are reserved for special methods that can be invoked. The special methods are build, throw, emit, join, lt, gt, eq, bool, str, addr, and len.

Special methods can be defined or overridden for classes. E.g., one can define a __len__ of a class or __bool__ and use a class in boolean expressions.

Reserved Method Outputs As these methods are reserved, their output types are predefined. Ensuring your output type matches the method call is vital, as any mismatch will result in failure.

Special Method Signatures

Special Method	Description	Signature
__build__	Build	`(self X, <any> other) → (<any> value)`
__throw__	Throw	`(self X) → (<any> String)`
__emit__	Emit	undefined
__join__	Join	`(self X, <any> X) → (<any> X)`
__lt__	Less Than	`(self X, <any> X) → (<any> Bool)`
__gt__	Greater Than	`(self X, <any> X) → (<any> Bool)`
__eq__	Equal To	`(self X, <any> X) → (<any> Bool)`
__bool__	Bool	`(self X) → (<any> Bool)`
__str__	String	`(self X) → (<any> String)`
__addr__	Address	`(self X) → (<any> Address)`
__len__	Length	`(self X) → (<any> U64)`

These methods must be called in coco using the __ at start and end of the method name.

coco Class

class TooLong:
    method __throw__()->(err String):
        yield err "string too long"

endpoint invokable TestLen(s String) -> (l U64):
    memory l1 = len(s)
    memory l2 = s.__len__()
    if l2 > 10:
        memory tl = TooLong{}
        throw tl

    if l1 != l2:
        memory ts = f"Lengths not equal {l1} != {l2}".__throw__()
        throw ts

    yield l l1