Kernel-E

From Erights

Latest revision as of 18:01, 13 May 2011

Kernel-E is the subset of the E language which is understood by evaluators. Full E is converted to Kernel-E by expansion.

XXX needs more info

Node classes

The following node types may occur in a Kernel-E program. The hierarchy indicates subtype relationships.

• ENode (abstract)
  • EExpr (abstract) — evaluate to a value
    • AssignExpr — assignment
    • BindingExpr (given guard-based auditing) — extract binding of a noun
    • CallExpr
    • CatchExpr
    • DefineExpr — match a pattern against a value
    • EscapeExpr — nonlocal exits
    • FinallyExpr — cleanup block
    • HideExpr
    • IfExpr
    • LiteralExpr
    • MetaContextExpr
    • MetaStateExpr
    • NounExpr
    • ObjectExpr — create an object
    • SeqExpr — evaluate in order, return last value
    • UnspecifiedExpr — placeholder for signature redactions
  • Pattern (abstract) — match a value and succeed or fail
    • NounPattern — patterns which bind one noun
      • BindingPattern (given guard-based auditing) — bind to a given binding object
      • FinalPattern — bind to a FinalSlot with a given value
      • VarPattern — bind to a VarSlot or GuardedSlot with a given value
    • IgnorePattern — discard value, possibly testing with a guard first
    • ListPattern — match each part of a tuple
    • ViaPattern — transform the specimen
  • EScriptoid (abstract) (proposed) — defines the behavior of an ObjectExpr
    • EMatcher — various uses
    • EScript — object behavior as a set of EMethod
  • EMethod
  • AuditorExprs (proposed) — see ObjectExpr

Formerly kernel nodes

These node types were once part of Kernel-E but have been removed or made non-kernel.

• SlotExpr, SlotPattern — now nonkernel in terms of BindingExpr and BindingPattern
• MatchBindExpr — now nonkernel in terms of DefineExpr
• SuchThatPattern — now nonkernel in terms of ViaPattern

Objects implied by Kernel-E semantics

Kernel-E semantics involves the following specific object types:

• A method matcher's pattern is matched against a Tuple[String, ConstList].
• IfExpr coerces to Boolean.
• ListPattern coerces to ConstList.
• XXX Details of miranda methods.
• XXX Are there any kernel expressions that return null?.

XXX This list may not be complete. The original work here was done in 2006. —Kevin Reid 13:01, 13 May 2011 (CDT)