Class: Eggshell::ExpressionEvaluator

Inherits:
Object
  • Object
show all
Defined in:
lib/eggshell/expression-evaluator.rb,
lib/eggshell/expression-evaluator/lexer.rb,
lib/eggshell/expression-evaluator/parser.rb,
lib/eggshell/expression-evaluator/evaluator.rb

Defined Under Namespace

Modules: Parser Classes: Evaluator, Lexer

Constant Summary collapse

ESCAPE_MAP = 
{
  '\\n'=> "\n",
  '\\r' => "\r",
  '\\t' => "\t",
  "\\(" => "(",
  "\\)" => ")",
  "\\{" => "{",
  "\\}" => "}",
  "\\[" => "[",
  "\\]" => "]",
  "\\'" => "'",
  '\\"' => '"'
}.freeze
OP_ASSIGN = 
'='.to_sym
OP_EQQ = 
'==='.to_sym
OP_EQ = 
'=='.to_sym
OP_NEQ = 
'!='.to_sym
OP_MATCH = 
'=~'.to_sym
OP_NMATCH = 
'!=~'.to_sym
OP_MULTIPLY = 
'*'.to_sym
OP_DIVIDE = 
'/'.to_sym
OP_ADD = 
'+'.to_sym
OP_SUBTRACT = 
'-'.to_sym
OPERATOR_MAP =

Values give corresponding order of precedence

{
  OP_ASSIGN => 1000,
  OP_EQQ => 999,
  OP_EQ => 998,
  OP_NEQ => 998,
  OP_MATCH => 997,
  OP_NMATCH => 997,
  '<'.to_sym => 990,
  '<='.to_sym => 990,
  '>'.to_sym => 990,
  '>='.to_sym => 990,
  '?'.to_sym => 900,
  ':'.to_sym => 899,
  '<<'.to_sym => 200,
  '>>'.to_sym => 200,
  '~'.to_sym => 200,
  '&'.to_sym => 200,
  '|'.to_sym => 199,
  OP_MULTIPLY => 150,
  OP_DIVIDE => 150,
  '%'.to_sym => 150,
  '^'.to_sym => 150,
  OP_ADD => 100,
  OP_SUBTRACT => 100,
  '&&'.to_sym => 99,
  '||'.to_sym => 99
}.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(vars = nil, funcs = nil) ⇒ ExpressionEvaluator 



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# File 'lib/eggshell/expression-evaluator.rb', line 59

def initialize(vars = nil, funcs = nil)
  @vars = vars || {}
  @funcs = funcs || {}
  @cache = {}
  @parser = Parser::DefaultParser.new
  #@evaluator = Evaluator.new(@vars, @funcs)
  @func_whitelist = {}
  @func_wl_alias = {}
end

Instance Attribute Details

#funcs ⇒ Object (readonly)

Returns the value of attribute funcs.



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# File 'lib/eggshell/expression-evaluator.rb', line 172

def funcs
  @funcs
end

#parser ⇒ Object (readonly)

Returns the value of attribute parser.



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# File 'lib/eggshell/expression-evaluator.rb', line 172

def parser
  @parser
end

#vars ⇒ Object (readonly)

Returns the value of attribute vars.



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# File 'lib/eggshell/expression-evaluator.rb', line 172

def vars
  @vars
end

Class Method Details

.op_eval(lop, op, rop) ⇒ Object 



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# File 'lib/eggshell/expression-evaluator.rb', line 305

def self.op_eval(lop, op, rop)
  #$stderr.write "op_eval:\n\t#{lop.inspect} #{op.inspect} #{rop.inspect}\n"
  if (lop.is_a?(Numeric) && rop.is_a?(Numeric))
    if op == OP_MATCH || op == OP_NMATCH
      raise Exception.new("'#{op}' can only be used with strings -- #{lop} #{op} #{rop}")
    end
    return lop.send(op, rop)
  elsif op == OP_EQQ
    return lop === rop
  elsif rop == :empty && (op == OP_EQ || op == OP_NEQ)
    # essentially (lop == false || lop == nil || lop == '') [==|!=] true
    # @todo other conditions to check empty?
    return (lop == false || lop == nil || lop == '').send(op, true)
  elsif lop.is_a?(String)
    e = nil
    if op == OP_MULTIPLY
      if rop.is_a?(Numeric)
        return lop * rop
      else
        e = "multiply string with numeric, #{rop.class} given"
      end
    elsif op == OP_MATCH || op == OP_NMATCH
      if rop.is_a?(String)
        m = lop.match(rop)
        if op == OP_NMATCH
          m = m == nil ? true : false
        end
        return m
      else
        e = "'#{op}' expects right operand to be string, #{rop.class} given"
      end
    elsif op == OP_ADD
      return lop + rop
    end
        
    raise Exception.new(e) if e
  elsif lop.is_a?(Array)
    if op == OP_MULTIPLY && rop.is_a?(Numeric)
      return lop * rop
    elsif (op == OP_ADD || op == OP_SUBTRACT) && rop.is_a?(Array)
      return lop.send(op, rop)
    end
    raise Exception.new("unsupported operation: #{lop.class} #{op} #{rop.class}")
  else
    
  end
end

Instance Method Details

#evaluate(statement, do_parse = true, cache = true, vtable = nil, ftable = nil) ⇒ Object 



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# File 'lib/eggshell/expression-evaluator.rb', line 184

def evaluate(statement, do_parse = true, cache = true, vtable = nil, ftable = nil)
  vtable = @vars if !vtable.is_a?(Hash)
  ftable = @funcs if !ftable.is_a?(Hash)
  parsed = statement
  #$stderr.write "!!! #{vtable.inspect} // #{@vars.inspect} !!!\n"
  #$stderr.write "parsed = #{parsed.inspect}||vtable=#{vtable.inspect}\n"
  if !statement.is_a?(Array)
    return statement if !do_parse || !statement.is_a?(String)
    parsed = parse(statement, cache)
  elsif parsed[0].is_a?(Symbol)
    parsed = [parsed]
    #$stderr.write "^^ fixed up\n"
  end

  ret = nil
  parsed.each do |frag|
    ftype = frag[0]
    if ftype == :op
      # [:op, [operand, operator, operand(, operator, operand, ...)]]
      # z contains the start index of the operator-operand list. if the first operator is '=',
      # reserve first operand as var reference and evaluate everything after '=' before storing
      # into var ref
      z = 0
      oplist = frag[1]
      if oplist[1] == OP_ASSIGN
        if !oplist[0].is_a?(Array) || oplist[0][0] != :var
          raise Exception.new("Illegal assignment to non-variable: #{frag[1][0].inspect}")
        end
        z = 2
      end

      op_val = oplist[z]
      if op_val.is_a?(Array)
        op_val = op_val[0] == :var ? var_access(op_val) : evaluate([oplist[z]], false)
      end

      z += 1
      while z < oplist.length
        op = oplist[z]
        rop = oplist[z+1]
        if rop.is_a?(Array)
          rop = rop[0] == :var ? var_access(rop) : evaluate([rop])
        end
        op_val = self.class.op_eval(op_val, op.to_sym, rop)
        z += 2
      end
      ret = op_val
      
      # var assignment; return true for successful set or false otherwise
      if oplist[1] == OP_ASSIGN
        ret = var_access(oplist[0], nil, ret)
      end
    elsif ftype == :op_tern
      cond = frag[1].is_a?(Array) ? evaluate(frag[1]) : frag[1]
      if cond
        ret = frag[2].is_a?(Array) ? evaluate(frag[2], false) : frag[2]
      else
        ret = frag[3].is_a?(Array) ? evaluate(frag[3], false) : frag[3]
      end
    elsif ftype == :func
      fname = frag[1]
      ns, name = fname.split(':')
      if !name
        name = ns
        ns = ':'
        fname = ':' + name
      else
        ns += ':'
      end

      handler = ftable[fname]
      if !handler && ftable[ns]
        handler = ftable[ns]
      end
      
      _args = []
      frag[2].each do |ele|
        _args << (ele.is_a?(Array) && ele[0].is_a?(Symbol) ? evaluate([ele]) : ele)
      end
      
      # 1. check for exact func name
      # 2. check for :exec_func
      if handler.respond_to?(name.to_sym)
        ret = handler.send(name.to_sym, *frag[2])
      elsif handler.respond_to?(:exec_func)
        ret = handler.exec_func(name, frag[2])
      end
    elsif ftype == :var
      #$stderr.write "<<< VAR\n"
      ret = var_access(frag, vtable)[0]
    elsif ftype == :group
      ret = evaluate(frag[1], false, cache, vtable)
    elsif ftype == :array
      arr = []
      i = 1
      while i < frag.length
        arr << (frag[i].is_a?(Array) ? evaluate(frag[i]) : frag[i])
        i += 1
      end
      ret = arr
    elsif ftype == :hash
      map = {}
      i = 1
      while i < frag.length
        k = frag[i]
        v = frag[i+1]
        k = evaluate(k) if k.is_a?(Array) && k[0].is_a?(Symbol)
        v = evaluate(v) if v.is_a?(Array) && v[0].is_a?(Symbol)
        map[k] = v
        i += 2
      end
      ret = map
    elsif !ftype.is_a?(Symbol)
      # assumes a literal
      ret = ftype
    end
  end
  
  ret
end

#get_function_aliases ⇒ Object 



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# File 'lib/eggshell/expression-evaluator.rb', line 155

def get_function_aliases
  ret = []
  @func_whitelist.each do |clz, map|
    ret << clz
    ret << "\tgetters: #{map[:get].keys.join(', ')}"
    ret << "\tsetters: #{map[:set].keys.join(', ')}"
  end
  @func_wl_alias.each do |clz, arr|
    ret << clz
    arr.each do |ali|
      star = @func_whitelist[ali] ? ' *' : ''
      ret << "\t=> #{ali}#{star}"
    end
  end
  ret
end

#has_function_alias(obj, func_name, type = :get) ⇒ Object 



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# File 'lib/eggshell/expression-evaluator.rb', line 135

def has_function_alias(obj, func_name, type = :get)
  clz = obj.is_a?(Class) ? obj.name : obj.class.name
  if @func_whitelist[clz] && @func_whitelist[clz][type][func_name]
    return true
  end
  
  ret = false
  if @func_wl_alias[clz]
    @func_wl_alias[clz].each do |ali|
      ali = @func_whitelist[ali]
      if ali && ali[type][func_name]
        ret = true
        break
      end
    end
  end
  
  return ret
end

#parse(statement, cache = true) ⇒ Object 



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# File 'lib/eggshell/expression-evaluator.rb', line 174

def parse(statement, cache = true)
  if cache
    parsed = @cache[statement]
    return parsed if parsed
  end

  @cache[statement] = @parser.parse(statement)
  return @cache[statement].clone
end

#register_function_alias(obj) ⇒ Object

The function whitelist expects a given object’s class to be a direct mapping into the whitelist. Use this method to register all super classes and interfaces of the given object that can be looked up if a mapping fails.



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# File 'lib/eggshell/expression-evaluator.rb', line 120

def register_function_alias(obj)
  clz = obj.is_a?(Class) ? obj : obj.class
  ptr = []
  clz.ancestors.each do |anc|
    next if anc == clz
    ptr << anc.name
  end
  @func_wl_alias[clz.name] = ptr
end

#register_function_whitelist(clz, getters, setters = nil) ⇒ Object

Registers 1+ getters and/or setters for a given class/module, avoiding need to alias or proxy methods to use ‘get_` and `set_` names.



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# File 'lib/eggshell/expression-evaluator.rb', line 98

def register_function_whitelist(clz, getters, setters = nil)
  if !clz.is_a?(String)
    clz = clz.name if clz.is_a?(Class)
    #clz = clz.name if clz.is_a?(Class)
  end
  @func_whitelist[clz] = {:get => {}, :set => {}}
  if getters.is_a?(Array)
    getters.each do |get|
      @func_whitelist[clz][:get][get] = true
    end
  end
  if setters.is_a?(Array)
    setters.each do |set|
      @func_whitelist[clz][:set][set] = true
    end
  end
end

#register_functions(handler, names = nil, ns = '') ⇒ Object

TODO:

expand mapping of functions so that we don’t have to check each

Maps 1 or more virtual function names to a handler.

Virtual functions take the form of ‘funcname` or `ns:funcname`. When registering functions, all function names will be mapped to the same namespace that’s passed in. If no names are given, the handler will be set to handle all function calls in the namespace.

The handler should either handle 1-to-1 function calls (e.g. ‘ns:func` goes to `handler.func()`) or it should contain the following method signature: `def exec_func(funcname, args = [])`. If there’s a 1-to-1 match, arguments are expanded into individual arguments instead of an array.

time a func is referenced whether handler can handle it (only applies to explicit names)



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# File 'lib/eggshell/expression-evaluator.rb', line 85

def register_functions(handler, names = nil, ns = '')
  names = names.split(',') if names.is_a?(String) && names.strip != ''
  if names.is_a?(Array)
    names.each do |name|
      @funcs["#{ns}:#{name}"] = handler
    end
  else
    @funcs["#{ns}:"] = handler
  end
end

#resolve_function_alias(obj) ⇒ Object 



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# File 'lib/eggshell/expression-evaluator.rb', line 130

def resolve_function_alias(obj)
  clz = obj.is_a?(Class) ? obj.name : obj.class.name
  return @func_wl_alias[clz] || []
end

#test_func(*args) ⇒ Object 



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# File 'lib/eggshell/expression-evaluator.rb', line 482

def test_func(*args)
  puts "test_func: #{args.inspect}"
end

#var_access(var, vtable = nil, set_var = :nope) ⇒ Object

Gets or sets a variable reference. If reference is a string, an exact match is looked for in vars table, otherwise an array (complex reference) is expected. If a value is given in the ‘set_var` parameter, an attempt is made to assign the value (provided there’s a suitable method to handle setting).

For a complex variable reference, iteratively chains a parent var with a child variable identifier. The return value is an array that returns the resolved value, its parent var, and the final identifier. In the case of setting, the resolved value is {true} if a setter was found and {false} otherwise.

otherwise an array with a parsed variable expression is expected. A symbol is used as a check since symbols are not supported in expressions.



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# File 'lib/eggshell/expression-evaluator.rb', line 369

def var_access(var, vtable = nil, set_var = :nope)
  vtable = @vars if !vtable
  if var.is_a?(String)
    return :empty if var == 'empty'
    if var.match(/^[a-zA-Z_][a-zA-Z0-9_\.]*$/)
      if vtable.has_key?(var)
        if set_var == :nope
          return [vtable[var], nil, nil]
        else
          vtable[var] = set_var
          return [true, nil, nil]
        end
      end
    end
    var = @parser.parse(var)
  end
  
  return :empty if var[1] == 'empty'

  ptr_lst = nil
  ptr = vtable
  i = 0
  parts = var
  set_point = set_var == :nope ? parts.length + 1 : parts.length - 1
  while (i < parts.length && ptr != nil)
    part = parts[i]
    ptr_lst = ptr
    if part == :var
      key = parts[i+1]
      if ptr.is_a?(Hash)
        if i == set_point
          ptr[key] = set_var
          ptr = true
        elsif ptr[key]
          ptr = ptr[key]
          if ptr != nil
            i += 2
            next
          end
        else
          ptr = nil
        end
      else
        ptr = nil
      end
    elsif part[0] == :index_access
      idx = part[1]
      if idx.is_a?(Array)
        idx = var_access(idx)[0]
        if idx == nil
          ptr = nil
          break
        end
      end
      if (ptr.is_a?(Array) || ptr.is_a?(Hash))
        if i == set_point
          ptr[idx] = set_var
          ptr = true
        else
          ptr = ptr[idx]
        end
      else
        ptr = nil
      end
    elsif part[0] == :member_access
      if ptr.is_a?(Hash)
        if i == set_point
          ptr[part[1]] = set_var
          ptr = true
        else
          ptr = ptr[part[1]]
        end
      else
        prefix = 'get_'
        type = :get
        if i == set_point
          prefix = 'set_'
          type = :set
        end

        mname = (prefix + part[1]).to_sym
        tgt = nil

        if ptr.respond_to?(mname)
          tgt = mname
        elsif has_function_alias(ptr, part[1], type)
          tgt = part[1].to_sym
        end
        if tgt
          if type == :set
            ptr.send(tgt, set_var)
            ptr = true
          else
            ptr = ptr.send(tgt)
          end
        else
          ptr = nil
        end
      end
    elsif part[0] == :func
      # @todo throw exception if this is set_point?
      # @todo what happens when we have `var[something](fn_args)`
      ptr = evaluate(part, false)
    end
    i += 1
  end
  return [ptr, ptr_lst, parts[-1]]
  #return do_ptr ? ptr_lst : ptr
end

#var_set(var, val) ⇒ Object 



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# File 'lib/eggshell/expression-evaluator.rb', line 479

def var_set(var, val)
end