"not" instruction

docs/syntax.md

@@ -50,6 +50,12 @@ Reference a list (a list reference) with an asterisk:
   setlist *myList $value1 $value2 # and so on
 ```
 
+Add comments with a `#`:
+
+```
+  # This is a comment
+```
+
 ## Keywords
 
 Note: &var can be replaced with any direct reference. $value can be replaced with a literal value or a value reference. %1 can be replaced with a line reference.
@@ -188,6 +194,12 @@ Checks if two values are not equal. Outputs a boolean to a direct reference.
 
 Usage: `inequal $value $value &var`
 
+#### not
+
+Negates a boolean.
+
+Usage: `not $value &var`
+
 #### greater
 
 Checks if the left value is greater than the right value. Outputs a boolean to a direct reference.

src/main.cpp

@@ -53,7 +53,7 @@ enum class Instructions {
     Jump, If,
     Stdout, Stdin, Stdlnout,
     Add, Subtract, Multiply, Divide,
-    Equal, Inequal, Greater, Lesser,
+    Equal, Inequal, Greater, Lesser, Not,
     End, Set, Empty,
     Setlist, Getlistat, Setlistat, Getlistsize, Listappend, Listprepend,
     Getstrcharat, Getstrsize,
@@ -1264,6 +1264,35 @@ Literal exec(vector<Instruction> in) {
                     variables[varName] = final;
                 }
                 break;
+            /*
+                not instruction
+                Negates a boolean.
+            */
+            case Instructions::Not:
+                if (l.args.size() < 2) {
+                    error("Could not find all arguments required for Not inbuilt");
+                }
+                {
+
+                    Literal boolean;
+                    
+                    if (holds_alternative<Literal>(l.args[0])) {
+                        if (holds_alternative<bool>(get<Literal>(l.args[0]).val)) {
+                            boolean.val = !(get<bool>(get<Literal>(l.args[0]).val));
+                        } else {
+                            error("First argument of not must be a boolean literal");
+                        }
+                    } else {
+                        error("First argument of not must be a boolean literal");
+                    }
+
+                    if (holds_alternative<Direct>(l.args[1])) {
+                        variables[get<Direct>(l.args[1]).varName] = boolean;
+                    } else {
+                        error("Second argument of not must be a direct reference");
+                    }
+                }
+                break;
             /*
                 greater instruction
                 This instruction checks if the left value is greater than the right value