diff --git a/graphics.cpp b/graphics.cpp
index 2cde550..3781352 100644
--- a/graphics.cpp
+++ b/graphics.cpp
@@ -43,7 +43,7 @@ void Graphics::plot(const Vec2bf &from, const Vec2bf &to)
 {
     for (double i = 0.0; i < this->w; i++) {
         for (double j = 0.0; j < this->h; j++) {
-            BigFloat f = from.x + (i / this->w) * (from.x - to.x);
+            BigFloat f =  (from.x - to.x) * from.x + (i / this->w);
         }
     }
 }
diff --git a/utils.h b/utils.h
index dda874d..da39918 100644
--- a/utils.h
+++ b/utils.h
@@ -45,7 +45,7 @@ public:
     std::string to_str();
     BigFloat operator / (const BigFloat &f);
 
-    inline BigFloat operator - (const BigFloat &f)
+    inline BigFloat operator - (const BigFloat &f) const
     {
         BigFloat res = BigFloat(f.precision);
         mpfr_sub(res.val, this->val, f.val, MPFR_RNDD);
@@ -53,7 +53,7 @@ public:
         return res;
     }
 
-    inline BigFloat operator - (const double d)
+    inline BigFloat operator - (const double d) const
     {
         BigFloat res = BigFloat(this->precision);
         mpfr_sub_d(res.val, this->val, d, MPFR_RNDD);
@@ -61,7 +61,7 @@ public:
         return res;
     }
 
-    inline BigFloat operator * (const BigFloat &f)
+    inline BigFloat operator * (const BigFloat &f) const
     {
         BigFloat res = BigFloat(f.precision);
         mpfr_mul(res.val, this->val, f.val, MPFR_RNDD);
@@ -69,7 +69,7 @@ public:
         return res;
     }
 
-    inline BigFloat operator * (const double d)
+    inline BigFloat operator * (const double d) const
     {
         BigFloat res = BigFloat(this->precision);
         mpfr_mul_d(res.val, this->val, d, MPFR_RNDD);
@@ -77,7 +77,7 @@ public:
         return res;
     }
 
-    inline BigFloat operator + (const BigFloat &f)
+    inline BigFloat operator + (const BigFloat &f) const
     {
         BigFloat res = BigFloat(f.precision);
         mpfr_add(res.val, this->val, f.val, MPFR_RNDD);
@@ -85,7 +85,7 @@ public:
         return res;
     }
 
-    inline BigFloat operator + (const double d)
+    inline BigFloat operator + (const double d) const
     {
         BigFloat res = BigFloat(this->precision);
         mpfr_add_d(res.val, this->val, d, MPFR_RNDD);