Class: Fusion::Interpreter::Env

Inherits:
Object
  • Object
show all
Defined in:
lib/fusion/interpreter/env.rb

Defined Under Namespace

Classes: DuplicateBinding

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(parent = nil) ⇒ Env

Returns a new instance of Env.



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# File 'lib/fusion/interpreter/env.rb', line 24

def initialize(parent = nil)
  @vars = {}     # pattern bindings, keyed by identifier
  @context = {}  # hidden interpreter context, keyed by symbol
  @parent = parent
end

Instance Attribute Details

#parent ⇒ Object (readonly)

Returns the value of attribute parent.



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# File 'lib/fusion/interpreter/env.rb', line 22

def parent
  @parent
end

Instance Method Details

#bind(name, value, checked: true) ⇒ Object

Pattern bindings:

  • Shadowing a binding from a parent Env is always allowed.
  • A duplicate identifier in the same Env is usually an error, but allowed on the REPL.


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# File 'lib/fusion/interpreter/env.rb', line 43

def bind(name, value, checked: true)
  if checked && @vars.key?(name)
    raise DuplicateBinding, name
  end

  @vars[name] = value
end

#child ⇒ Object 



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# File 'lib/fusion/interpreter/env.rb', line 30

def child
  Env.new(self)
end

#context(key) ⇒ Object 



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# File 'lib/fusion/interpreter/env.rb', line 78

def context(key)
  if @context.key?(key)
    @context[key]
  elsif @parent
    @parent.context(key)
  else
    :__unbound__
  end
end

#lookup(name) ⇒ Object 



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# File 'lib/fusion/interpreter/env.rb', line 51

def lookup(name)
  if @vars.key?(name)
    @vars[name]
  elsif @parent
    @parent.lookup(name)
  else
    :__unbound__
  end
end

#root ⇒ Object

The topmost ancestor — the binding-free root a run is built on. The interpreter loads files relative to it, so they stay isolated.



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# File 'lib/fusion/interpreter/env.rb', line 36

def root
  @parent ? @parent.root : self
end

#set_context(key, value) ⇒ Object

Hidden interpreter context:

  • :dir: the directory @-references resolve against (a path String).
  • :file: the current file's absolute path, used for error origins (a String; absent for inline/REPL code, which reports as origin "code" with file "").
  • :self: the current top-level unit's own Thunk, used for recursion via a bare @.
  • :jail: the run's jail root confining @-resolution (an absolute path String, or nil for unconfined). Set once on the root and, unlike the others, never overridden by a descendant.
  • :call_site: the innermost user-code file a stdlib body borrows for its errors (a String). Set on a stdlib function's clause env in Interpreter#apply; user/inline code derives its own and omits it.


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# File 'lib/fusion/interpreter/env.rb', line 73

def set_context(key, value)
  @context[key] = value
  self
end