Module types 

Type system for Seq

Based on cem2’s row polymorphism design with improvements. Supports stack effect declarations like: ( ..a Int – ..a Bool )

Computational Effects

Beyond stack effects, Seq tracks computational side effects using the | syntax:

• ( a -- b | Yield T ) - may yield values of type T (generators)
• Effects propagate through function calls
• strand.weave handles the Yield effect, strand.spawn requires pure quotations

Structs

Effect

Stack effect: transformation from input stack to output stack Example: ( ..a Int – ..a Bool ) means:

UnionTypeInfo

Type information for a union definition (used by type checker)

VariantFieldInfo

Information about a variant field

VariantInfo

Information about a union variant (used by type checker)

Enums

SideEffect

Computational side effects (beyond stack transformation)

StackType

Stack types with row polymorphism

Type

Base types in the language