Add exists instruction

docs/syntax.md

@@ -116,6 +116,12 @@ Gets the type of a variable. Outputs a string which can be "int", "double", "boo
 
 Usage: `gettype $value &var`
 
+#### exists
+
+Checks if a variable exists with a direct reference. If the variable exists, outputs true. Otherwise outputs false.
+
+Usage `exists &var1 &var2`
+
 #### setlist
 
 Allows you to initialize a list.

src/main.cpp

@@ -73,7 +73,7 @@ enum class Instructions {
     Stdout, Stdin, Stdlnout,
     Add, Subtract, Multiply, Divide,
     Equal, Inequal, Greater, Lesser, Not,
-    End, Set, Empty, Gettype,
+    End, Set, Empty, Gettype, Exists,
     Setlist, Getlistat, Setlistat, Getlistsize, Listappend, Listprepend,
     Getstrcharat, Getstrsize,
     Stoi, Stod, Tostring,
@@ -1655,6 +1655,30 @@ Literal exec(vector<Instruction> in, bool executingFunction) {
                     
                 }
 
+                break;
+            case Instructions::Exists:
+                if (l.args.size() < 2) {
+                    error("Could not find all arguments required for Exists inbuilt");
+                }
+                {
+                    Direct ref1;
+                    if (holds_alternative<Direct>(l.args[0])) {
+                        ref1 = get<Direct>(l.args[0]);
+                    } else {
+                        error("First argument of exists must be a direct reference");
+                    }
+
+                    Direct ref2;
+                    if (holds_alternative<Direct>(l.args[1])) {
+                        ref2 = get<Direct>(l.args[1]);
+                    }
+
+                    if (variables.find(ref1.varName) != variables.end()) {
+                        variables[ref2.varName].val = true; 
+                    } else {
+                        variables[ref2.varName].val = false;
+                    }
+                }
                 break;
             /*
                 fun instruction
@@ -2113,6 +2137,7 @@ vector<Instruction> parser(vector<vector<string>> in) {
                 else if (i == "end") newInst.inst = Instructions::End;
                 else if (i == "set") newInst.inst = Instructions::Set;
                 else if (i == "gettype") newInst.inst = Instructions::Gettype;
+                else if (i == "exists") newInst.inst = Instructions::Exists;
                 else if (i == "setlist") newInst.inst = Instructions::Setlist;
                 else if (i == "setlistat") newInst.inst = Instructions::Setlistat;
                 else if (i == "getlistat") newInst.inst = Instructions::Getlistat;