diff --git a/include/common.h b/include/common.h
index 45a2c7c..372cf07 100644
--- a/include/common.h
+++ b/include/common.h
@@ -289,4 +289,29 @@ ObjectBase* Get(const ObjectList* input)
  return ob->Get(name->Value());
 }
 
+// Simple conversion functions
+inline bool str2double(const char* str, double* res)
+{
+ char* pos;
+ *res=strtod(str,&pos);
+ if('\0'!=*pos) return false; else return true;
+}
+
+inline bool str2int(const char* str, int64_t* res)
+{
+ char* pos;
+ *res=strtoll(str,&pos,0);
+ if('\0'!=*pos) return false; else return true;
+}
+
+inline bool str2uint(const char* str, uint64_t* res)
+{
+ char* pos;
+ *res=strtoull(str,&pos,0);
+ if('\0'!=*pos) return false; else return true;
+}
+
+inline bool str2double(const std::string& str, double* res) {return str2double(str.c_str(),res);}
+inline bool str2int(const std::string& str, int64_t* res) {return str2int(str.c_str(),res);}
+inline bool str2uint(const std::string& str, int64_t* res) {return str2uint(str.c_str(),res);}
 #endif
diff --git a/src/parser/lexical.l b/src/parser/lexical.l
index 0adcbc8..9c8cb07 100644
--- a/src/parser/lexical.l
+++ b/src/parser/lexical.l
@@ -101,8 +101,21 @@ std::string str;
                                                 }
 [a-zA-Z][a-zA-Z0-9_]*                           COUT(MOREDEBUG)<<"NAME("<<yytext<<")"; BEGIN(PARSE); yylval_param->str=new std::string(yytext); setyyllocp; yynextsym; return NAME;
 <PARSE>[+\-*/^]                                 COUT(MOREDEBUG)<<" OPERATION("<<yytext<<")"; setyyllocp; yynextsym; return yytext[0];
-<PARSE>[0-9]+   				COUT(MOREDEBUG)<<" INTEGER("<<yytext<<")"; yylval_param->i=atoll(yytext); setyyllocp; yynextsym; return INTEGER;
-<PARSE>[0-9]+(\.[0-9]*)?([eE][+-][0-9]+)?	COUT(MOREDEBUG)<<" REAL("<<yytext<<")"; yylval_param->r=atof(yytext); setyyllocp; yynextsym; return REAL;
+<PARSE>[0-9]+   				{
+						 COUT(MOREDEBUG)<<" INTEGER("<<yytext<<")";
+						 if(!str2int(yytext,&yylval_param->i)) yyerrormessage(std::string("failed conversion to integer of ")+yytext+" at position "+std::to_string(yyextra->state.curpos),-1);
+						 yylval_param->i=atoll(yytext);
+						 setyyllocp;
+						 yynextsym;
+						 return INTEGER;
+						}
+<PARSE>[0-9]+(\.[0-9]*)?([eE][+-][0-9]+)?	{
+						 COUT(MOREDEBUG)<<" REAL("<<yytext<<")";
+						 if(!str2double(yytext,&yylval_param->r)) yyerrormessage(std::string("failed conversion to double of ")+yytext+" at position "+std::to_string(yyextra->state.curpos),-1);
+						 setyyllocp;
+						 yynextsym;
+						 return REAL;
+						}
 <PARSE>[TF]                                     COUT(MOREDEBUG)<<" BOOL("<<yytext<<")"; yylval_param->b=(yytext[0]=='T')?true:false; setyyllocp; yynextsym; return BOOL;
 <PARSE>\(					COUT(MOREDEBUG)<<" OBRACE()"; setyyllocp; yynextsym; return OBRACE;
 <PARSE>\)					COUT(MOREDEBUG)<<" CBRACE()"; setyyllocp; yynextsym; return CBRACE;