Class: Heist::Runtime

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Defined in:
lib/heist/runtime/runtime.rb,
lib/heist/runtime/frame.rb,
lib/heist/runtime/scope.rb,
lib/heist/runtime/stack.rb,
lib/heist/runtime/binding.rb,
lib/heist/runtime/data/cons.rb,
lib/heist/runtime/stackless.rb,
lib/heist/runtime/data/value.rb,
lib/heist/runtime/data/vector.rb,
lib/heist/runtime/callable/macro.rb,
lib/heist/runtime/data/character.rb,
lib/heist/runtime/callable/syntax.rb,
lib/heist/runtime/data/expression.rb,
lib/heist/runtime/data/identifier.rb,
lib/heist/runtime/callable/function.rb,
lib/heist/runtime/callable/macro/tree.rb,
lib/heist/runtime/callable/continuation.rb,
lib/heist/runtime/callable/macro/matches.rb,
lib/heist/runtime/callable/macro/expansion.rb

Overview

Runtime objects represent instances of the Heist runtime environment. Each Runtime defines a top-level Scope, into which are injected the standard set of primitive functions and special forms as defined in lib/builtin.

User code runs in another scope descended from the top-level. This is done so that user-level redefinitions of built-in functions do not break other built-in functions that refer to the redefined names; lexical scoping ensures that built-in functions can only refer to other bindings in the top-level scope so user-level bindings do not affect the built-in library functions.

Runtime exposes several methods from the user-level Scope object, allowing runtime objects to be used as interfaces for defining functions, eval’ing code and running source files.

Defined Under Namespace

Modules: Expression Classes: Binding, Body, Character, Cons, Continuation, FileScope, Frame, Function, Identifier, Macro, Scope, Stack, Stackless, Syntax, Value, Vector

Constant Summary collapse

BUILTIN_LIBRARIES = 
%w[primitives syntax compiled_library]

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ Runtime

A Runtime is initialized using a set of options. The available options include the following, all of which are false unless you override them yourself:

  • :continuations: set to true to enable call/cc

  • :lazy: set to true to enable lazy evaluation

  • :unhygienic: set to true to disable macro hygiene



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# File 'lib/heist/runtime/runtime.rb', line 46

def initialize(options = {})
  @lazy          = !!options[:lazy]
  @continuations = !!options[:continuations]
  @hygienic      = !options[:unhygienic]
  
  @top_level  = Scope.new(self)
  @user_scope = Scope.new(@top_level)
  @stack      = stackless? ? Stackless.new : Stack.new
  
  load_builtins(options)
  @start_time = Time.now.to_f
end

Instance Attribute Details

#stack ⇒ Object

Returns the value of attribute stack.



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# File 'lib/heist/runtime/runtime.rb', line 34

def stack
  @stack
end

#top_level ⇒ Object

Returns the value of attribute top_level.



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# File 'lib/heist/runtime/runtime.rb', line 34

def top_level
  @top_level
end

#user_scope ⇒ Object

Returns the value of attribute user_scope.



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# File 'lib/heist/runtime/runtime.rb', line 34

def user_scope
  @user_scope
end

Instance Method Details

#elapsed_time ⇒ Object

Returns the length of time the Runtime has been alive for, as a number in microseconds.



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# File 'lib/heist/runtime/runtime.rb', line 74

def elapsed_time
  (Time.now.to_f - @start_time) * 1000000
end

#hygienic? ⇒ Boolean

Returns true iff the Runtime is using hygienic macros.

Returns:

  • (Boolean) 


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# File 'lib/heist/runtime/runtime.rb', line 82

def hygienic?; @hygienic; end

#info ⇒ Object 



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# File 'lib/heist/runtime/runtime.rb', line 97

def info
  [ "Heist Scheme interpreter v. #{ VERSION }",
    "Evaluation mode: #{ lazy? ? 'LAZY' : 'EAGER' }",
    "Continuations enabled? #{ stackless? ? 'NO' : 'YES' }",
    "Macros: #{ hygienic? ? 'HYGIENIC' : 'UNHYGIENIC' }\n\n"
  ] * "\n"
end

#lazy? ⇒ Boolean

Returns true iff the Runtime is using lazy evaluation.

Returns:

  • (Boolean) 


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# File 'lib/heist/runtime/runtime.rb', line 79

def lazy?; @lazy; end

#load_builtins(options = {}) ⇒ Object

To stop user-space redefinitions of built-in functions from breaking the standard library, we define builtins in a privileged scope, one up from the scope that user code runs in. We then bind the names in ‘user space’ to stop (set!) from reaching into our privileged top level.



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# File 'lib/heist/runtime/runtime.rb', line 63

def load_builtins(options = {})
  libraries = (options[:only] || BUILTIN_LIBRARIES) - (options[:except] || [])
  
  libraries.each do |library|
    @top_level.run(@top_level.expand_path(library))
  end
  @user_scope.each_var(&@user_scope.method(:[]=))
end

#stackless? ⇒ Boolean

Returns true iff the Runtime is using the faster Stackless evaluator, which does not support (call/cc).

Returns:

  • (Boolean) 


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# File 'lib/heist/runtime/runtime.rb', line 86

def stackless?
  lazy? or not @continuations
end

#to_s ⇒ Object Also known as: inspect 



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# File 'lib/heist/runtime/runtime.rb', line 90

def to_s
  "#<runtime: #{ stackless? ? 'call/cc disabled' : 'call/cc enabled'
           }, #{ hygienic? ? 'hygienic' : 'unhygienic'
           }, #{ lazy? ? 'lazy' : 'eager' }>"
end