solves #1576

src/gdlc.g

@@ -137,8 +137,8 @@ tokens {
 	PARAEXPR_VN; // _VN Variable Number of parameters version
     DEC_REF_CHECK; // called from EvalRefCheck() (no temporary needed then)
     INC_REF_CHECK; // called from EvalRefCheck() (no temporary needed then)
-    POSTDEC;
-    POSTINC; 
+    POSTDEC;  //post-decrement : i--
+    POSTINC; // Post-increment : i++
     DECSTATEMENT; // as a statement
     INCSTATEMENT; // as a statement
     REF;        // expr pass by reference
@@ -156,7 +156,7 @@ tokens {
 	SYSVAR;
 //	UPLUS;
 	UMINUS;
-	VAR;     // varaible, referenced through index
+	VAR;     // variable, referenced through index
 	VARPTR;  // variable, referenced through pointer
     WHILE;
 }

src/prognode.cpp

@@ -906,6 +906,7 @@ void REF_CHECKVNNode::Parameter( EnvBaseT* actEnv)
   ProgNode::interpreter->_retTree = this->getNextSibling();
 }
 
+//eval the single parameter of a libFunDirect() function (cos(),sin() etc)
 bool ParameterNode::ParameterDirect( BaseGDL*& pval)
 {
   pval = this->getFirstChild()->Eval(); 

src/prognodeexpr.cpp

@@ -684,7 +684,10 @@ BaseGDL** DEREFNode::LEval()
 BaseGDL** QUESTIONNode::EvalRefCheck( BaseGDL*& rEval)
 {
   ProgNodeP branch = this->GetThisBranch();
-  return branch->EvalRefCheck( rEval);
+  rEval = branch->Eval();
+  return NULL;
+  //was:  //  return branch->EvalRefCheck( rEval);
+  // but crash as reported in  #1576 for "a=0 & b=0 & c=0 & z=cos( a ? b:c)" and other strange things.
 }  
 
 BaseGDL** QUESTIONNode::LEval()

src/prognodeexpr.hpp

@@ -109,6 +109,7 @@ class FCALL_LIB_RETNEWNode: public LeafNode
   BaseGDL* Eval();
 };
 
+//For nodes relative to a libFunDirect() function (cos(),sin() etc)
 class FCALL_LIB_DIRECTNode: public LeafNode
 {
   LibFunDirect libFunDirectFun;