Dynamic Type and Static Type

• Runtime vs Compile time
• Slow vs fast
• flexible vs inflexible

Strong Typing

• Sound type system: guarantees that a no type errors can occur at runtime
• cons
  • Some checks can only be done dynamically (Array bounds checking)
  • Such checking can cause serious performance degradation
  • Even so-called strongly typed languages often have “holes" in the type system (e.g. variant records in Pascal)

Type Equivalence

• If types are required to match, the question of what types are considered to be “equivalent" arises
• Structural equivalence requires equivalent structures
  • Identical basic types
  • Same type constructor applied to equivalent types
• Name equivalence considered types to be equal only if the same names are used
• C uses structural equivalence except for records

Type Signatures

• The signature of a procedure is a description of the types of its arguments and type of its result.
• i.e) sqrt : real -> real, mod: integer X integer -> integer

Polymorphic Procedures

• A procedure that has multiple type signatures is called polymorphic

Failure Of Type Checking Due To Aliasing, Variant Records, Subroutine Calls

Citation:

• Aho, Lam, Sethi, & Ullman, Compilers: Principles, Techniques, and Tools

• UT Austin CS375: Compilers by G.Novak.