diff --git a/Objects/LLang.l b/Objects/LLang.l
index 26d9121..3f2bef1 100644
--- a/Objects/LLang.l
+++ b/Objects/LLang.l
@@ -17,13 +17,26 @@ ws [ \t]+
 digits [0-9]
 intnum (0|[1-9]+{digits}*)
 floatnum (0|[1-9]+{digits}*)\.?{digits}*
-STRING \"(\\.|[^"\\])*\"
+STRING \"(\\.|[^"\\\n])*\"
 true True
 false False
 none None
 VAR [_]*[a-zA-Z][a-zA-Z0-9_]*
 EXIT exit[\(][\)]
 %%
+> {return GT;}
+>= {return GE;}
+\< {return LT;}
+\<= {return LE;}
+== {return EQ;}
+!= {return NE;}
+not {return NOT;}
+or {return OR;}
+and {return AND;}
+if {return IF;}
+while {return WHILE;}
+else {return ELSE;}
+print {return PRINT;}
 {true} {
     yylval.sym = install("",object,(LLObject*)LLBool_Make(1));
     return object;}
diff --git a/Objects/LLang.y b/Objects/LLang.y
index 99915d1..4a9aeda 100644
--- a/Objects/LLang.y
+++ b/Objects/LLang.y
@@ -1,12 +1,12 @@
 %{
 #include <stdio.h>
 #include "Lala.h"
+#include "vm.h"
 #include "abstract.h"
 #include "Symbol.h"
 extern void *code(Inst);
 #define code2(c1,c2) code(c1); code(c2);
 #define code3(c1,c2,c3) code(c1); code(c2); code(c3);
-
 void execerror(char *s, char *t);
 void yyerror (char *s);
 int yylex ();
@@ -22,19 +22,25 @@ int readfile = 0;
   Symbol *sym;
   Inst *inst;
 }
-%token <sym> object VAR BLTIN INDEF EXIT
-%type<inst> arraylist initarray
+%token <sym> object VAR BLTIN INDEF EXIT IF ELSE PRINT WHILE
+%type<inst> arraylist initarray asgn exp stmt stmtlist cond if end while
 
 %right '='
+%left OR
+%left AND
+%left GT GE LT LE EQ NE
 %left '+' '-'
 %left '*' '/'
-%left UNARYMINUS
+%left UNARYMINUS NOT
+%nonassoc LOWER_THAN_ELSE
+%nonassoc ELSE
 %%
 list:
   | list'\n'
   | list asgn '\n' {code2((Inst)pop,STOP);return 1;}
   | list exp '\n'  { code2(print,STOP);return 1;}
   | list error '\n' {initcode();printf(">>> ");yyerrok;}
+  | list stmt '\n' {code(STOP);return 1;}
   ;
 initarray: {code(makeArray);}
 ;
@@ -45,6 +51,35 @@ arraylist: arraylist','arraylist {}
 asgn: VAR '=' exp {code3(varpush,(Inst)$1,assign);}
     | exp '[' exp ']' '=' exp {code(ChangeValue);}
 ;
+stmt: exp {code((Inst)pop);}
+    | PRINT exp { code(print); $$ = $2;}
+    | while cond stmt end {
+        ($1)[1] = (Inst)$3;
+        ($1)[2] = (Inst)$4;
+      }
+    | if cond stmt end  %prec LOWER_THAN_ELSE{
+        ($1)[1] = (Inst)$3;
+        ($1)[3] = (Inst)$4;
+      }
+    | if cond stmt end ELSE stmt end {
+        ($1)[1] = (Inst)$3;
+        ($1)[2] = (Inst)$6;
+        ($1)[3] = (Inst)$7;
+      }
+    | '{' stmtlist '}' {printf("...");$$=$2;}
+;
+cond: exp  {code(STOP);$$=$1;}
+;
+if: IF {$$=code(ifcode);code3(STOP,STOP,STOP);}
+  ;
+while: WHILE {$$= code3(whilecode,STOP,STOP);}
+  ;
+end:  '\n'{code(STOP);$$=progp;}
+  ;
+stmtlist: {$$=progp;}
+      | stmtlist '\n' {printf("... ");}
+      | stmtlist stmt
+;
 exp:  object  { code2(constpush,(Inst)$1);}
       | VAR       {code3(varpush,(Inst)$1,eval);}
       | asgn
@@ -55,6 +90,15 @@ exp:  object  { code2(constpush,(Inst)$1);}
       | '(' exp ')'     { }
       |BLTIN  '(' exp ')' {code2(bltin,(Inst)$1->u.ptr);}
       |'-' exp %prec UNARYMINUS {code(negate);}
+      | exp GT exp {code(gt);}
+      | exp GE exp {code(ge);}
+      | exp LT exp {code(lt);}
+      | exp LE exp {code(le);}
+      | exp EQ exp {code(eq);}
+      | exp NE exp {code(ne);}
+      | exp AND exp {code(and);}
+      | exp OR exp {code(or);}
+      | NOT exp {$$=$2;code(not);}
       | EXIT {exit(0);}
       | initarray '['arraylist']' {code(STOP);}
       | exp '[' exp ']' {code(aArray);}
@@ -75,7 +119,7 @@ int main (int argc, char *argv[]){
   progname=argv[0];
   init();
   if(argc==1){
-    printf("Lala Lang v1.3 \n[GCC 8.2.1 20181127]\n");
+    printf("Lala Lang v1.4 \n[GCC 8.2.1 20181127]\n");
     setjmp(begin);
     printf(">>> ");
     for(initcode(); yyparse (); initcode()){
diff --git a/Objects/abstract.c b/Objects/abstract.c
index d5dd894..b4b72c8 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -194,3 +194,91 @@ int LL_FUNC_PRINT(LLObject* o,char* end){
     }
     return 0;
 }
+double LL_CONDITION_EVAL(LLObject* o){
+    double result = 0;
+    if(o==NULL)
+        return result;
+    if(o->ob_type==LLBoolTypeObject){
+        result = (double)((LLBoolObject*)o)->o_val;
+    }
+    if(o->ob_type==LLListTypeObject){
+        result =(double) ((LLEntryListObject*)o)->len;
+    }
+    if(o->ob_type==LLIntTypeObject){
+        result =(double) ((LLIntObject*)o)->o_val;
+    }
+    if(o->ob_type==LLFloatTypeObject){
+        result = (((LLFloatObject*)o)->o_val);
+    }
+    if(o->ob_type==LLStringTypeObject){
+        result = (double)((LLStringObject*)o)->len;
+    }
+    return result;
+}
+LLObject* LL_FUNC_GT(LLObject* a,LLObject* b){
+    int r1,r2;
+    if((a->ob_type!=b->ob_type)&&((a->ob_type == LLIntTypeObject || a->ob_type == LLFloatTypeObject ) && (b->ob_type == LLIntTypeObject || b->ob_type == LLFloatTypeObject)))
+        execerror("No se puede comparar!", NULL);
+    r1 = LL_CONDITION_EVAL(a);
+    r2 = LL_CONDITION_EVAL(b);
+    return (LLObject*)LLBool_Make(r1>r2);
+}
+LLObject* LL_FUNC_LT(LLObject*a,LLObject*b){
+    int r1,r2;
+    if((a->ob_type!=b->ob_type)&&((a->ob_type == LLIntTypeObject || a->ob_type == LLFloatTypeObject ) && (b->ob_type == LLIntTypeObject || b->ob_type == LLFloatTypeObject)))
+        execerror("No se puede comparar!", NULL);
+    r1 = LL_CONDITION_EVAL(a);
+    r2 = LL_CONDITION_EVAL(b);
+    return (LLObject*)LLBool_Make(r1<r2);
+}
+LLObject* LL_FUNC_GE(LLObject*a,LLObject*b){
+    int r1,r2;
+    if((a->ob_type!=b->ob_type)&&((a->ob_type == LLIntTypeObject || a->ob_type == LLFloatTypeObject ) && (b->ob_type == LLIntTypeObject || b->ob_type == LLFloatTypeObject)))
+        execerror("No se puede comparar!", NULL);
+    r1 = LL_CONDITION_EVAL(a);
+    r2 = LL_CONDITION_EVAL(b);
+    return (LLObject*)LLBool_Make(r1>=r2);
+}
+LLObject* LL_FUNC_LE(LLObject*a,LLObject*b){
+    int r1,r2;
+    if((a->ob_type!=b->ob_type)&&((a->ob_type == LLIntTypeObject || a->ob_type == LLFloatTypeObject ) && (b->ob_type == LLIntTypeObject || b->ob_type == LLFloatTypeObject)))
+        execerror("No se puede comparar!", NULL);
+    r1 = LL_CONDITION_EVAL(a);
+    r2 = LL_CONDITION_EVAL(b);
+    return (LLObject*)LLBool_Make(r1<=r2);
+}
+LLObject* LL_FUNC_EQ(LLObject*a,LLObject*b){
+    int r1,r2;
+    if((a->ob_type!=b->ob_type)&&((a->ob_type == LLIntTypeObject || a->ob_type == LLFloatTypeObject ) && (b->ob_type == LLIntTypeObject || b->ob_type == LLFloatTypeObject)))
+        execerror("No se puede comparar!", NULL);
+    if(a->ob_type==LLStringTypeObject && b->ob_type==LLStringTypeObject){
+        return (LLObject*)LLBool_Make(LLString_EQ(a,b));
+    }
+    r1 = LL_CONDITION_EVAL(a);
+    r2 = LL_CONDITION_EVAL(b);
+    return (LLObject*)LLBool_Make(r1==r2);
+}
+LLObject* LL_FUNC_NE(LLObject*a,LLObject*b){
+    if(a->ob_type!=b->ob_type){
+        return (LLObject*)LLBool_Make(1);
+    }
+    LLBoolObject* r = (LLBoolObject*)LL_FUNC_EQ(a,b);
+    r->o_val = !(r->o_val);
+    return (LLObject*)r;
+}
+LLObject* LL_FUNC_AND(LLObject*a,LLObject*b){
+    return (LLObject*)LLBool_Make(LL_CONDITION_EVAL(a)&&LL_CONDITION_EVAL(b));
+}
+LLObject* LL_FUNC_OR(LLObject*a,LLObject*b){
+    return (LLObject*)LLBool_Make(LL_CONDITION_EVAL(a)||LL_CONDITION_EVAL(b));
+}
+LLObject* LL_FUNC_NOT(LLObject*a){
+    return (LLObject*)LLBool_Make(!LL_CONDITION_EVAL(a));
+}
+LLObject* LL_FUNC_LEN(LLObject* a){
+    if(a->ob_type==LLListTypeObject)
+        return (LLObject*) LLInt_Make(((LLEntryListObject*)a)->len);
+    if(a->ob_type==LLStringTypeObject)
+        return (LLObject*) LLInt_Make(((LLStringObject*)a)->len);
+    execerror("BLINT 'len' no implementado", NULL);
+}
\ No newline at end of file
diff --git a/Objects/init.c b/Objects/init.c
index 7ab7387..f3da2d5 100644
--- a/Objects/init.c
+++ b/Objects/init.c
@@ -1,5 +1,16 @@
 #include "Lala.h"
+#include "abstract.h"
+#include "Symbol.h"
+#include "y.tab.h"
+static struct {	/*	Predefinidos */
+    char *name;
+    LLObject* (*func)();
+} builtins[] =	{
+        "len",	LL_FUNC_LEN,
+        0,	0
+};
 void init(){
+  Symbol *s;
   LLIntTypeObject = calloc(1,sizeof(LLTypeObject));
   LLStringTypeObject = calloc(1,sizeof(LLTypeObject));
   LLListTypeObject = calloc(1,sizeof(LLTypeObject));
@@ -25,5 +36,10 @@ void init(){
   c = malloc(sizeof(char)*14);
   strcpy(c,"<type 'None'>\0");
   LLNoneTypeObject->name = c;
+
+  for (int i = 0; builtins[i].name; i++) {
+        s = install(builtins[i].name, BLTIN, (LLObject*)LLNone_Make());
+        s->u.ptr = builtins[i].func;
+    }
   return;
 }
\ No newline at end of file
diff --git a/Objects/listObject.c b/Objects/listObject.c
index 996c695..b3997bd 100644
--- a/Objects/listObject.c
+++ b/Objects/listObject.c
@@ -93,8 +93,10 @@ LLEntryListObject* LLList_getrange(LLEntryListObject* e,int* pos1,int* pos2){
         return NULL;
     }
   }
-  if(pos1 !=0 && pos2!=0 && *pos1==*pos2)
-    return 0;
+  //if(pos1 !=0 && pos2!=0 && *pos1==*pos2)
+    //return 0;
+  if(start==end)
+      return 0;
   while(start->next!=end){
     aux = LLList_append(aux,start->o);
     start = start->next;
diff --git a/Objects/stringObject.c b/Objects/stringObject.c
index ebb26a8..210a63f 100644
--- a/Objects/stringObject.c
+++ b/Objects/stringObject.c
@@ -49,3 +49,6 @@ LLObject* LLString_MUL(LLObject* s,LLObject* i){
     cad[k+1]='\0';
     return (LLObject*)LLString_Make(cad);
 }
+int LLString_EQ(LLObject*a,LLObject*b){
+    return strcmp(((LLStringObject*)a)->o_sval,((LLStringObject*)b)->o_sval)==0;
+}
\ No newline at end of file
diff --git a/Objects/vm.c b/Objects/vm.c
index 1d001c4..e6d5994 100644
--- a/Objects/vm.c
+++ b/Objects/vm.c
@@ -1,8 +1,5 @@
-#include "abstract.h"
-#include "Symbol.h"
-#include "Lala.h"
+#include "vm.h"
 #include "y.tab.h"
-
 extern void execerror(char *s, char *t);
 #define NSTACK  256
 static  Datum  stack[NSTACK];  /* la pila */
@@ -166,6 +163,103 @@ void emptypush(){
   d.val = 0;
   push(d);
 }
+
+void ifcode(){
+    Datum d;
+    Inst  *savepc  = pc;	/* parte then */
+    execute(savepc+3);	/*  condición   */
+    d  =  pop();
+    if(LL_CONDITION_EVAL(d.val))
+        execute(*((Inst   **)(savepc)));
+    else if(*((Inst  **)(savepc+1)))   /*  ¿parte else?   */
+        execute(*(( Inst  **) (savepc+1)));
+    pc  =  *((Inst  **)(savepc+2));	/*  siguiente proposición   */
+}
+
+void whilecode(){
+    Datum d;
+    Inst *savepc = pc;
+    execute(savepc+2);
+    d = pop();
+    while(LL_CONDITION_EVAL(d.val)){
+        execute(*((Inst  **)(savepc)));
+        execute(savepc+2);
+        d = pop();
+    }
+    pc = *((Inst  **)(savepc+1));
+}
+
+void gt() {
+    Datum d1,  d2;
+    d2 = pop();
+    d1 = pop();
+    d1.val  = LL_FUNC_GT(d1.val,d2.val);
+    push(d1);
+}
+
+void lt(){
+    Datum d1,  d2;
+    d2 = pop();
+    d1 = pop();
+    d1.val  = LL_FUNC_LT(d1.val,d2.val);
+    push(d1);
+}
+
+void ge( ) {
+    Datum d1,  d2;
+    d2  = pop();
+    d1  = pop();
+    d1.val = LL_FUNC_GE(d1.val,d2.val);
+    push(d1) ;
+}
+
+void le() {
+    Datum d1,  d2;
+    d2   =  pop();
+    d1   =  pop();
+    d1.val = LL_FUNC_LE(d1.val,d2.val);
+    push(d1);
+}
+
+void eq( ) {
+    Datum d1,  d2;
+    d2  = pop();
+    d1  = pop();
+    d1.val =LL_FUNC_EQ(d1.val,d2.val);
+    push(d1);
+}
+
+void ne(){
+    Datum d1, d2;
+    d2 = pop();
+    d1 = pop();
+    d1.val = LL_FUNC_NE(d1.val,d2.val);
+    push(d1);
+}
+
+void and(){
+    Datum d1,   d2;
+    d2   = pop();
+    d1   = pop();
+    d1.val = LL_FUNC_AND(d1.val,d2.val);
+    push(d1);
+}
+
+void or(){
+    Datum d1, d2;
+    d2 = pop();
+    d1 = pop();
+    d1.val = LL_FUNC_OR(d1.val,d2.val);
+    push(d1);
+}
+
+void not( ){
+    Datum d;
+    d = pop();
+    d.val = LL_FUNC_NOT(d.val);
+    push(d);
+}
+
 Inst   *code(Inst f) /*   instalar una instrucción u operando   */
 {
     Inst *oprogp = progp;
diff --git a/include/Symbol.h b/include/Symbol.h
index 936fbf5..c1501c1 100644
--- a/include/Symbol.h
+++ b/include/Symbol.h
@@ -17,20 +17,5 @@ typedef struct Symbol {
 } Symbol;
 
 Symbol *install(char *s,int t, LLObject*), *lookup(char *s);
-
-typedef union Datum {   /* tipo de la pila del intérprete */
-    LLObject*  val;
-    Symbol  *sym; } Datum;
-
-extern Datum pop();
-
-typedef void (*Inst)();  /* instrucción de máquina */
-
-#define STOP    (Inst) 0
-extern  Inst prog[];
-
-extern  void eval(), addo(), subo(), mulo(), divo(),negate();
-extern void  assign(), bltin(), varpush(), constpush(), print(),makeArray(),execute(Inst* p);
-extern void aArray(),ChangeValue(),getSubArray(),emptypush();
-
+typedef void (*Inst)();
 #endif
diff --git a/include/abstract.h b/include/abstract.h
index ab387c2..65cd6ee 100644
--- a/include/abstract.h
+++ b/include/abstract.h
@@ -12,5 +12,16 @@ LLObject* LL_FUNC_AACCESS(LLObject*,LLObject*);
 int LL_FUNC_PRINT(LLObject*,char*);
 LLObject* LL_FUNC_AREPLACE(LLObject*,LLObject*,LLObject*);
 LLObject* LL_FUNC_GETSUBARRAY(LLObject*,LLObject*,LLObject*);
+double LL_CONDITION_EVAL(LLObject*);
+LLObject* LL_FUNC_GT(LLObject*,LLObject*);
+LLObject* LL_FUNC_LT(LLObject*,LLObject*);
+LLObject* LL_FUNC_GE(LLObject*,LLObject*);
+LLObject* LL_FUNC_LE(LLObject*,LLObject*);
+LLObject* LL_FUNC_EQ(LLObject*,LLObject*);
+LLObject* LL_FUNC_NE(LLObject*,LLObject*);
+LLObject* LL_FUNC_AND(LLObject*,LLObject*);
+LLObject* LL_FUNC_OR(LLObject*,LLObject*);
+LLObject* LL_FUNC_NOT(LLObject*);
+LLObject* LL_FUNC_LEN(LLObject*);
 #define LL_NOT_IMPLEMENTED 0
 #endif
diff --git a/include/stringObject.h b/include/stringObject.h
index 55663da..d2018da 100644
--- a/include/stringObject.h
+++ b/include/stringObject.h
@@ -15,4 +15,5 @@
   LLObject* LLString_CAT(LLObject*,LLObject*);
   LLObject* LLString_String(LLObject*);
   LLObject* LLString_MUL(LLObject*,LLObject*);
+  int LLString_EQ(LLObject*,LLObject*);
 #endif
diff --git a/include/vm.h b/include/vm.h
new file mode 100644
index 0000000..104d951
--- /dev/null
+++ b/include/vm.h
@@ -0,0 +1,22 @@
+#ifndef __VM_H__
+#define __VM_H__
+
+#include "Symbol.h"
+#include "abstract.h"
+#include "Lala.h"
+typedef union Datum {   /* tipo de la pila del intérprete */
+    LLObject*  val;
+    Symbol  *sym; } Datum;
+
+extern Datum pop();
+
+typedef void (*Inst)();  /* instrucción de máquina */
+
+#define STOP    (Inst) 0
+extern  Inst prog[];
+
+void eval(), addo(), subo(), mulo(), divo(),negate();
+void  assign(), bltin(), varpush(), constpush(), print(),makeArray(),execute(Inst* p);
+void aArray(),ChangeValue(),getSubArray(),emptypush(),ifcode(),whilecode();
+void gt(),ge(),lt(),le(),eq(),ne(),and(),or(),not();
+#endif
\ No newline at end of file