diff --git a/commandline.cpp b/commandline.cpp
index e29dda53..bb9fb609 100644
--- a/commandline.cpp
+++ b/commandline.cpp
@@ -79,7 +79,15 @@ EX namespace arg {
   EX const char* argcs() { return args().c_str(); }
   EX int argi() { return atoi(argcs()); }
   EX unsigned arghex() { return strtoll(argcs(), NULL, 16); }
-  EX ld argf() { return parseld(args()); }
+  EX ld argf() { 
+    try {
+      return parseld(args());
+      }
+    catch(hr_parse_exception& ex) {
+      println(hlog, "error parsing commandline parameters: ", ex.s);
+      exit(1);
+      }
+    }
   EX bool argis(const string& s) { if(args()[0] == '-' && args()[1] == '-') return args().substr(1) == s; return args() == s; }
   
   EX void shift_arg_formula(ld& x, const reaction_t& r IS(reaction_t())) {
diff --git a/dialogs.cpp b/dialogs.cpp
index 26510b7b..43444ed9 100644
--- a/dialogs.cpp
+++ b/dialogs.cpp
@@ -743,17 +743,20 @@ EX namespace dialog {
     }
   
   EX void apply_edit() {
-    exp_parser ep;
-    ep.s = ne.s;
-    ld x = real(ep.parse());
-    if(!ep.ok()) return;
-    if(ne.sc.positive && x <= 0) return;
-    *ne.editwhat = x;
-    if(ne.intval) *ne.intval = ldtoint(*ne.editwhat);
-    #if CAP_ANIMATIONS
-    if(ne.animatable) anims::animate_parameter(*ne.editwhat, ne.s, reaction ? reaction : reaction_final);    
-    #endif
-    if(reaction) reaction();
+    try {
+      exp_parser ep;
+      ep.s = ne.s;    
+      ld x = ep.rparse();
+      if(ne.sc.positive && x <= 0) return;
+      *ne.editwhat = x;
+      if(ne.intval) *ne.intval = ldtoint(*ne.editwhat);
+      #if CAP_ANIMATIONS
+      if(ne.animatable) anims::animate_parameter(*ne.editwhat, ne.s, reaction ? reaction : reaction_final);    
+      #endif
+      if(reaction) reaction();
+      }
+    catch(hr_parse_exception&) { 
+      }
     }
 
   EX void bound_low(ld val) {
diff --git a/hypgraph.cpp b/hypgraph.cpp
index b23cb6f0..6961cde6 100644
--- a/hypgraph.cpp
+++ b/hypgraph.cpp
@@ -833,7 +833,13 @@ EX void applymodel(hyperpoint H, hyperpoint& ret) {
       ep.extra_params["uy"] = H[1];
       ep.extra_params["uz"] = H[2];
       ep.s = models::formula;
-      cld res = ep.parse();
+      cld res;
+      try {
+        res = ep.parse();
+        }
+      catch(hr_parse_exception&) {
+        res = 0;
+        }
       ret[0] = real(res);
       ret[1] = imag(res);
       ret[2] = 0;
diff --git a/pattern2.cpp b/pattern2.cpp
index cae7d71c..e575a34d 100644
--- a/pattern2.cpp
+++ b/pattern2.cpp
@@ -1577,7 +1577,12 @@ EX namespace patterns {
       }
         
     ep.s = formula;
-    return ep.parse();
+    try {
+      return ep.parse();
+      }
+    catch(hr_parse_exception& ex) {
+      return 0;
+      }
     }
   
   EX hookset<int(cell*)> *hooks_generate_canvas;
diff --git a/screenshot.cpp b/screenshot.cpp
index 4cca797e..67705fd6 100644
--- a/screenshot.cpp
+++ b/screenshot.cpp
@@ -575,7 +575,12 @@ void apply_animated_parameters() {
   ap_changes = 0;
   for(auto &ap: aps) {
     if(*ap.value != ap.last) continue;
-    *ap.value = parseld(ap.formula);
+    try {
+      *ap.value = parseld(ap.formula);
+      }
+    catch(hr_parse_exception&) {
+      continue;
+      }
     if(*ap.value != ap.last) {
       if(ap.reaction) ap.reaction();
       ap_changes++;
diff --git a/util.cpp b/util.cpp
index 01052335..ffabf845 100644
--- a/util.cpp
+++ b/util.cpp
@@ -121,6 +121,11 @@ EX bool appears(const string& haystack, const string& needle) {
   }
 
 #if HDR
+struct hr_parse_exception : hr_exception {
+  string s;
+  hr_parse_exception(const string& z) : s(z) {}
+  };
+
 struct exp_parser {
   string s;
   int at;
@@ -129,7 +134,7 @@ struct exp_parser {
   map<string, cld> extra_params;
 
   bool ok() { return at == isize(s); }
-  char next(int step=0) { if(at >= isize(s)-step || at == -1) return 0; else return s[at+step]; }
+  char next(int step=0) { if(at >= isize(s)-step) return 0; else return s[at+step]; }
   
   bool eat(const char *c) {
     int orig_at = at;
@@ -150,10 +155,14 @@ struct exp_parser {
 
   cld parsepar() {
     cld res = parse();
-    if(next() != ')') { at = -1; return res; }
-    at++;
+    force_eat(")");
     return res;
     }
+  
+  void force_eat(const char *c) {
+    skip_white();
+    if(!eat(c)) throw hr_parse_exception("expected: " + string(c));
+    }
 
   };
 #endif
@@ -188,24 +197,24 @@ cld exp_parser::parse(int prio) {
   else if(eat("to01(")) { res = parsepar(); return atan(res) / ld(M_PI) + ld(0.5); }
   else if(eat("ifp(")) {
     cld cond = parse(0);
-    if(snext() != ',') {at = -1; return 0; } at++;
+    force_eat(",");
     cld yes = parse(0);
-    if(snext() != ',') {at = -1; return 0; } at++;
+    force_eat(",");
     cld no = parsepar();
     return real(cond) > 0 ? yes : no;
     }  
   else if(eat("wallif(")) {
     cld val0 = parse(0);
-    if(snext() != ',') {at = -1; return 0; } at++;
+    force_eat(",");
     cld val1 = parsepar();
     if(real(extra_params["p"]) >= 3.5) return val0;
     else return val1;
     }
   else if(eat("rgb(")) {     
     cld val0 = parse(0);
-    if(snext() != ',') {at = -1; return 0; } at++;
+    force_eat(",");
     cld val1 = parse(0);
-    if(snext() != ',') {at = -1; return 0; } at++;
+    force_eat(",");
     cld val2 = parsepar();
     switch(int(real(extra_params["p"]) + .5)) {
       case 1: return val0;
@@ -223,11 +232,9 @@ cld exp_parser::parse(int prio) {
         name += c, at++;
       else break;
       }
-    if(snext() != '=') { at = -1; return 0; }
-    at++;
+    force_eat("=");
     cld val = parse(0);
-    if(snext() != ',') { at = -1; return 0; }
-    at++;
+    force_eat(",");
     dynamicval<cld> d(extra_params[name], val);
     return parsepar();
     }
@@ -250,7 +257,7 @@ cld exp_parser::parse(int prio) {
     else if(number == "i") res = cld(0, 1);
     else if(number == "p" || number == "pi") res = M_PI;
     else if(number == "" && next() == '-') { at++; res = -parse(prio); }
-    else if(number == "") at = -1;
+    else if(number == "") throw hr_parse_exception("number missing");
     else if(number == "s") res = ticks / 1000.;
     else if(number == "ms") res = ticks;
     else if(number[0] == '0' && number[1] == 'x') res = strtoll(number.c_str()+2, NULL, 16);
@@ -262,7 +269,7 @@ cld exp_parser::parse(int prio) {
     else if(number == "shot") res = inHighQual ? 1 : 0;
     else if(extra_params.count(number)) res = extra_params[number];
     else if(params.count(number)) res = params.at(number);
-    else if(number[0] >= 'a' && number[0] <= 'z') at = -1;
+    else if(number[0] >= 'a' && number[0] <= 'z') throw hr_parse_exception("unknown value: " + number);
     else { std::stringstream ss; res = 0; ss << number; ss >> res; }
     }
   while(true) {