Module: Odin::Transform::Expr

Defined in:
lib/odin/transform/transform_expr.rb

Overview

Compiles an infix arithmetic formula string into a tree of existing verbs at parse time. No runtime evaluator: the result is an ordinary verb expression, so arithmetic runs through the deterministic verbs (add, subtract, multiply, divide, mod, negate, pow, and a whitelist of numeric functions). Variables resolve under an explicit bindings object passed as the second argument: in %expr “a + b” @.vars, the name a reads @.vars.a.

Precedence, high to low:

1. parentheses, function call
2. ^ power (right-associative)
3. unary - / +   (looser than ^, so -2^2 = -(2^2) = -4; (-2)^2 = 4)
4. * / %  (left-associative)
5. + -    (left-associative)

Defined Under Namespace

Classes: ExprSyntaxError, Parser, Token

Constant Summary collapse

BINARY_OP = 
{ "+" => "add", "-" => "subtract", "*" => "multiply", "/" => "divide", "%" => "mod" }.freeze
FUNCTIONS = 
{
  "abs" => { verb: "abs", min: 1, max: 1 },
  "floor" => { verb: "floor", min: 1, max: 1 },
  "ceil" => { verb: "ceil", min: 1, max: 1 },
  "trunc" => { verb: "trunc", min: 1, max: 1 },
  "sqrt" => { verb: "sqrt", min: 1, max: 1 },
  "round" => { verb: "round", min: 1, max: 2 },
  "pow" => { verb: "pow", min: 2, max: 2 },
  "min" => { verb: "minOf", min: 1, max: Float::INFINITY },
  "max" => { verb: "maxOf", min: 1, max: Float::INFINITY }
}.freeze

Class Method Summary collapse

Class Method Details

.compile(formula, binding_path = nil) ⇒ Object 



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# File 'lib/odin/transform/transform_expr.rb', line 46

def compile(formula, binding_path = nil)
  Parser.new(tokenize(formula), binding_path).parse
end

.literal(text, is_float) ⇒ Object 



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# File 'lib/odin/transform/transform_expr.rb', line 98

def literal(text, is_float)
  value = is_float ? Types::DynValue.of_float(text.to_f) : Types::DynValue.of_integer(text.to_i)
  LiteralExpr.new(value)
end

.tokenize(src) ⇒ Object 



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# File 'lib/odin/transform/transform_expr.rb', line 50

def tokenize(src)
  tokens = []
  i = 0
  len = src.length
  while i < len
    c = src[i]
    if c =~ /\s/
      i += 1
      next
    end
    if c =~ /[0-9]/
      j = i
      is_float = false
      j += 1 while j < len && src[j] =~ /[0-9]/
      if src[j] == "."
        is_float = true
        j += 1
        j += 1 while j < len && src[j] =~ /[0-9]/
      end
      if src[j] == "e" || src[j] == "E"
        is_float = true
        j += 1
        j += 1 if src[j] == "+" || src[j] == "-"
        j += 1 while j < len && src[j] =~ /[0-9]/
      end
      tokens << Token.new(:num, src[i...j], is_float)
      i = j
      next
    end
    if c =~ /[A-Za-z_]/
      j = i
      j += 1 while j < len && src[j] =~ /[A-Za-z0-9_.]/
      tokens << Token.new(:ident, src[i...j], false)
      i = j
      next
    end
    case c
    when "(" then tokens << Token.new(:lparen, c, false)
    when ")" then tokens << Token.new(:rparen, c, false)
    when "," then tokens << Token.new(:comma, c, false)
    when "+", "-", "*", "/", "%", "^" then tokens << Token.new(:op, c, false)
    else raise ExprSyntaxError, "unexpected character '#{c}'"
    end
    i += 1
  end
  tokens
end

.verb_node(verb, args) ⇒ Object 



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# File 'lib/odin/transform/transform_expr.rb', line 103

def verb_node(verb, args)
  VerbExpr.new(verb, args, custom: false)
end