diff --git a/dialogs.cpp b/dialogs.cpp
index c2334704..7e434ca0 100644
--- a/dialogs.cpp
+++ b/dialogs.cpp
@@ -599,6 +599,68 @@ namespace dialog {
   
   reaction_t extra_options;
 
+  struct exp_parser {
+    string s;
+    int at;
+    exp_parser() { at = 0; }
+
+    bool ok() { return at == isize(s); }
+    char next() { if(at == isize(s) || at == -1) return 0; else return s[at]; }
+    
+    bool eat(const char *c) {
+      int orig_at = at;
+      while(*c && *c == next()) at++, c++;
+      if(*c == 0) return true;
+      else at = orig_at;
+      return false;
+      }
+
+    ld parse(int prio = 0) {
+      ld res;
+      if(eat("sin(")) res = sin(parsepar());
+      else if(eat("cos(")) res = cos(parsepar());
+      else if(eat("sinh(")) res = sinh(parsepar());
+      else if(eat("cosh(")) res = cosh(parsepar());
+      else if(eat("asin(")) res = asin(parsepar());
+      else if(eat("acos(")) res = acos(parsepar());
+      else if(eat("asinh(")) res = asinh(parsepar());
+      else if(eat("acosh(")) res = acosh(parsepar());
+      else if(eat("exp(")) res = exp(parsepar());
+      else if(eat("log(")) res = log(parsepar());
+      else if(next() == '(') at++, res = parsepar();
+      else {
+        string number;
+        while(true) {
+          char c = next();
+          if((c >= '0' && c <= '9') || among(c, 'e', 'p', '.'))
+            number += c, at++;
+          else break;
+          }
+        if(number == "e") res = exp(1);
+        else if(number == "p") res = M_PI;
+        else if(number == "") at = -1;
+        else if(number[0] >= 'a' && number[0] <= 'z') at = -1;
+        else { std::stringstream ss; res = 0; ss << number; ss >> res; }
+        }
+      while(true) {
+        if(next() == '+' && prio == 0) at++, res = res + parse(1);
+        else if(next() == '-' && prio == 0) at++, res = res - parse(1);
+        else if(next() == '*' && prio <= 1) at++, res = res * parse(2);
+        else if(next() == '/' && prio <= 1) at++, res = res / parse(2);
+        else if(next() == '^') at++, res = pow(res, parse(3));
+        else break;
+        }
+      return res;
+      }
+
+    ld parsepar() {
+      ld res = parse();
+      if(next() != ')') { at = -1; return res; }
+      at++;
+      return res;
+      }  
+    };
+
   void affect(char kind) {
 
     if(ne.intval) {
@@ -607,8 +669,10 @@ namespace dialog {
       }
     else {
       if(kind == 's') {
-        ld x;
-        sscanf(ne.s.c_str(), LDF, &x);
+        exp_parser ep;
+        ep.s = ne.s;
+        ld x = ep.parse();
+        if(!ep.ok()) return;
         if(ne.sc.positive && x <= 0) return;
         *ne.editwhat = x;
         }
@@ -730,7 +794,7 @@ namespace dialog {
     
     keyhandler = [] (int sym, int uni) {
       handleNavigation(sym, uni);
-      if((uni >= '0' && uni <= '9') || (uni == '.' && !ne.intval) || (uni == '-' && !ne.sc.positive)) {
+      if((uni >= '0' && uni <= '9') || (uni == '.' && !ne.intval) || among(uni, '+', '-', '*', '/', '^', '(', ')') || (uni >= 'a' && uni <= 'z')) {
         ne.s += uni;
         affect('s');
         }