Fixed the order of symbols, optional symbol set input, to_proc for basics

Author: rajithv

lib/symengine.rb

@@ -33,8 +33,8 @@ def Function(n)
     def evalf(operand, prec=53, real=false)
         return _evalf(operand, prec, real)
     end
-    def lambdify(exp)
-      eval(SymEngine::Utils::lambdify_code(exp))
+    def lambdify(exp, syms=nil)
+      eval(SymEngine::Utils::lambdify_code(exp, syms))
     end
   end
   module Utils
@@ -45,9 +45,13 @@ def evalf_dirichlet_eta(exp)
       def evalf_zeta(exp)
           SymEngine::evalf(SymEngine::zeta(exp))
       end
-      def lambdify_code(exp)
-        sym_map = exp.free_symbols.map { |sym| sym.to_s}.sort.join(",")
-        str = exp.to_s
+      def lambdify_code(exp, syms=nil)
+        str = exp.to_s  
+        if syms == nil
+          sym_map = exp.free_symbols.map {|sym| sym.to_s}.map {|s| { index: str.index(s), sym: s} }.sort_by{ |item| item[:index] }.map {|item| item[:sym] }.join(',')
+        else
+          sym_map = syms.join(",")
+        end
         str.gsub!(/[\d\.]+/, 'Rational(\0,1)')
         replacements = { sin:"Math.sin", cos: "Math.cos", tan: "Math.tan",
                          asin:"Math.asin", acos: "Math.acos", atan: "Math.atan",

lib/symengine/basic.rb

@@ -11,8 +11,10 @@ def free_symbols
     end
 
     def abs
-        return SymEngine::abs(self)
+        SymEngine::abs(self)
+    end
+    def to_proc
+        SymEngine::lambdify(self)
     end
-    
   end
 end