diff --git a/src/script/block.rs b/src/script/block.rs
index a62311f..a1650f1 100644
--- a/src/script/block.rs
+++ b/src/script/block.rs
@@ -310,7 +310,7 @@ pub mod to_runnable {
                         if builtin.can_take(&rargs.iter().map(|v| v.out()).collect()) {
                             RStatementEnum::BuiltinFunction(builtin, rargs)
                         } else {
-                            todo!("ERR: Builtin function with wrong args - this isn't a proper error yet, sorry.");
+                            todo!("ERR: Builtin function \"{v}\" with wrong args - this isn't a proper error yet, sorry.");
                         }
                     } else {
                         return Err(ToRunnableError::UseOfUndefinedFunction(v.clone()));
diff --git a/src/script/builtins.rs b/src/script/builtins.rs
index 1f2b01a..a6212c8 100644
--- a/src/script/builtins.rs
+++ b/src/script/builtins.rs
@@ -134,7 +134,7 @@ impl BuiltinFunction {
                 if input.len() >= 1 {
                     input[0].types.iter().all(|v| {
                         if let VSingleType::Function(v) = v {
-                            if v.iter().any(|(i, _)| i.len() == input.len()) {
+                            if v.iter().any(|(i, _)| i.len() == input.len() - 1) {
                                 eprintln!("Warn: Function inputs aren't type checked yet!)");
                                 // TODO!
                                 true
diff --git a/src/script/val_data.rs b/src/script/val_data.rs
new file mode 100644
index 0000000..6d91034
--- /dev/null
+++ b/src/script/val_data.rs
@@ -0,0 +1,143 @@
+use std::{
+    fmt::Debug,
+    sync::{Arc, Mutex},
+    thread::JoinHandle,
+    time::Duration,
+};
+
+use super::{
+    block::RFunction,
+    val_type::{VSingleType, VType},
+};
+
+#[derive(Clone, Debug)]
+pub struct VData {
+    // parents: Vec<()>,
+    pub data: VDataEnum,
+}
+
+#[derive(Clone, Debug)]
+pub enum VDataEnum {
+    Bool(bool),
+    Int(isize),
+    Float(f64),
+    String(String),
+    Tuple(Vec<VData>),
+    List(VType, Vec<VData>),
+    Function(RFunction),
+    Thread(VDataThread, VType),
+    Reference(Arc<Mutex<VData>>),
+}
+
+impl VData {
+    pub fn out(&self) -> VType {
+        VType {
+            types: vec![self.out_single()],
+        }
+    }
+    pub fn out_single(&self) -> VSingleType {
+        match &self.data {
+            VDataEnum::Bool(..) => VSingleType::Bool,
+            VDataEnum::Int(..) => VSingleType::Int,
+            VDataEnum::Float(..) => VSingleType::Float,
+            VDataEnum::String(..) => VSingleType::String,
+            VDataEnum::Tuple(v) => VSingleType::Tuple(v.iter().map(|v| v.out()).collect()),
+            VDataEnum::List(t, _) => VSingleType::List(t.clone()),
+            VDataEnum::Function(f) => VSingleType::Function(f.input_output_map.clone()),
+            VDataEnum::Thread(_, o) => VSingleType::Thread(o.clone()),
+            VDataEnum::Reference(r) => r.lock().unwrap().out_single(),
+        }
+    }
+    pub fn get(&self, i: usize) -> Option<Self> {
+        self.data.get(i)
+    }
+}
+
+impl VDataEnum {
+    pub fn to(self) -> VData {
+        VData { data: self }
+    }
+}
+
+// get()
+impl VDataEnum {
+    pub fn get(&self, i: usize) -> Option<VData> {
+        match self {
+            Self::Bool(..)
+            | Self::Int(..)
+            | Self::Float(..)
+            | Self::Function(..)
+            | Self::Thread(..) => None,
+            Self::String(s) => match s.chars().nth(i) {
+                // Slow!
+                Some(ch) => Some(Self::String(format!("{ch}")).to()),
+                None => None,
+            },
+            Self::Tuple(v) | Self::List(_, v) => v.get(i).cloned(),
+            Self::Reference(r) => r.lock().unwrap().get(i),
+        }
+    }
+}
+#[derive(Clone)]
+pub struct VDataThread(Arc<Mutex<VDataThreadEnum>>);
+impl VDataThread {
+    pub fn try_get(&self) -> Option<VData> {
+        match &*self.lock() {
+            VDataThreadEnum::Running(_) => None,
+            VDataThreadEnum::Finished(v) => Some(v.clone()),
+        }
+    }
+    pub fn get(&self) -> VData {
+        let dur = Duration::from_millis(100);
+        loop {
+            match &*self.lock() {
+                VDataThreadEnum::Running(v) => {
+                    while !v.is_finished() {
+                        std::thread::sleep(dur);
+                    }
+                }
+                VDataThreadEnum::Finished(v) => return v.clone(),
+            }
+        }
+    }
+    pub fn lock(&self) -> std::sync::MutexGuard<VDataThreadEnum> {
+        let mut mg = self.0.lock().unwrap();
+        match &*mg {
+            VDataThreadEnum::Running(v) => {
+                if v.is_finished() {
+                    let m = std::mem::replace(
+                        &mut *mg,
+                        VDataThreadEnum::Finished(VData {
+                            data: VDataEnum::Bool(false),
+                        }),
+                    );
+                    match m {
+                        VDataThreadEnum::Running(v) => {
+                            *mg = VDataThreadEnum::Finished(v.join().unwrap())
+                        }
+                        _ => unreachable!(),
+                    }
+                }
+            }
+            _ => (),
+        }
+        mg
+    }
+}
+impl Debug for VDataThread {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match &*self.lock() {
+            VDataThreadEnum::Running(_) => write!(f, "(thread running)"),
+            VDataThreadEnum::Finished(v) => write!(f, "(thread finished: {v})"),
+        }
+    }
+}
+pub enum VDataThreadEnum {
+    Running(JoinHandle<VData>),
+    Finished(VData),
+}
+impl VDataThreadEnum {
+    pub fn to(self) -> VDataThread {
+        VDataThread(Arc::new(Mutex::new(self)))
+    }
+}
diff --git a/src/script/val_type.rs b/src/script/val_type.rs
new file mode 100644
index 0000000..3d14b21
--- /dev/null
+++ b/src/script/val_type.rs
@@ -0,0 +1,182 @@
+use std::{fmt::Debug, ops::BitOr};
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct VType {
+    pub types: Vec<VSingleType>,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum VSingleType {
+    Bool,
+    Int,
+    Float,
+    String,
+    Tuple(Vec<VType>),
+    List(VType),
+    Function(Vec<(Vec<VSingleType>, VType)>),
+    Thread(VType),
+    Reference(Box<Self>),
+}
+
+impl VSingleType {
+    // None => Cannot get, Some(t) => getting can return t or nothing
+    pub fn get(&self, i: usize) -> Option<VType> {
+        match self {
+            Self::Bool | Self::Int | Self::Float | Self::Function(..) | Self::Thread(..) => None,
+            Self::String => Some(VSingleType::String.into()),
+            Self::Tuple(t) => t.get(i).cloned(),
+            Self::List(t) => Some(t.clone()),
+            Self::Reference(r) => r.get(i),
+        }
+    }
+}
+impl VType {
+    pub fn get(&self, i: usize) -> Option<VType> {
+        let mut out = VType { types: vec![] };
+        for t in &self.types {
+            out = out | t.get(i)?; // if we can't use *get* on one type, we can't use it at all.
+        }
+        Some(out)
+    }
+}
+
+impl VSingleType {
+    pub fn get_any(&self) -> Option<VType> {
+        match self {
+            Self::Bool | Self::Int | Self::Float | Self::Function(..) | Self::Thread(..) => None,
+            Self::String => Some(VSingleType::String.into()),
+            Self::Tuple(t) => Some(t.iter().fold(VType { types: vec![] }, |a, b| a | b)),
+            Self::List(t) => Some(t.clone()),
+            Self::Reference(r) => r.get_any(),
+        }
+    }
+}
+impl VType {
+    pub fn get_any(&self) -> Option<VType> {
+        let mut out = VType { types: vec![] };
+        for t in &self.types {
+            out = out | t.get_any()?; // if we can't use *get* on one type, we can't use it at all.
+        }
+        Some(out)
+    }
+}
+
+impl VType {
+    /// Returns a vec with all types in self that aren't covered by rhs. If the returned vec is empty, self fits in rhs.
+    pub fn fits_in(&self, rhs: &Self) -> Vec<VSingleType> {
+        let mut no = vec![];
+        for t in &self.types {
+            // if t doesnt fit in any of rhs's types
+            if !rhs.types.iter().any(|r| t.fits_in(r)) {
+                no.push(t.clone())
+            }
+        }
+        no
+    }
+    pub fn inner_types(&self) -> VType {
+        let mut out = VType { types: vec![] };
+        for t in &self.types {
+            for it in t.inner_types() {
+                out = out | it.to();
+            }
+        }
+        out
+    }
+    pub fn contains(&self, t: &VSingleType) -> bool {
+        self.types.contains(t)
+    }
+}
+impl BitOr for VType {
+    type Output = Self;
+    fn bitor(self, rhs: Self) -> Self::Output {
+        let mut types = self.types;
+        for t in rhs.types {
+            if !types.contains(&t) {
+                types.push(t)
+            }
+        }
+        Self { types }
+    }
+}
+impl BitOr<&VType> for VType {
+    type Output = Self;
+    fn bitor(self, rhs: &Self) -> Self::Output {
+        let mut types = self.types;
+        for t in &rhs.types {
+            if !types.contains(t) {
+                types.push(t.clone())
+            }
+        }
+        Self { types }
+    }
+}
+
+impl VSingleType {
+    pub fn to(self) -> VType {
+        VType { types: vec![self] }
+    }
+    pub fn inner_types(&self) -> Vec<VSingleType> {
+        match self {
+            Self::Tuple(v) => {
+                let mut types = vec![];
+                for it in v {
+                    // the tuple values
+                    for it in &it.types {
+                        // the possible types for each value
+                        if !types.contains(it) {
+                            types.push(it.clone());
+                        }
+                    }
+                }
+                types
+            }
+            Self::List(v) => v.types.clone(),
+            _ => vec![],
+        }
+    }
+    pub fn fits_in(&self, rhs: &Self) -> bool {
+        match (self, rhs) {
+            (Self::Bool, Self::Bool)
+            | (Self::Int, Self::Int)
+            | (Self::Float, Self::Float)
+            | (Self::String, Self::String) => true,
+            (Self::Bool | Self::Int | Self::Float | Self::String, _) => false,
+            (Self::Tuple(a), Self::Tuple(b)) => {
+                if a.len() == b.len() {
+                    a.iter().zip(b.iter()).all(|(a, b)| a.fits_in(b).is_empty())
+                } else {
+                    false
+                }
+            }
+            (Self::Tuple(_), _) => false,
+            (Self::List(a), Self::List(b)) => a.fits_in(b).is_empty(),
+            (Self::List(_), _) => false,
+            (Self::Function(a), Self::Function(b)) => 'func_out: {
+                for a in a {
+                    'search: {
+                        for b in b {
+                            if a.1.fits_in(&b.1).is_empty()
+                                && a.0.iter().zip(b.0.iter()).all(|(a, b)| *a == *b)
+                            {
+                                break 'search;
+                            }
+                        }
+                        break 'func_out false;
+                    }
+                }
+                true
+            }
+            (Self::Function(..), _) => false,
+            (Self::Thread(a), Self::Thread(b)) => a.fits_in(b).is_empty(),
+            (Self::Thread(..), _) => false,
+            (Self::Reference(r), Self::Reference(b)) => r.fits_in(b),
+            (Self::Reference(_), _) => false,
+        }
+    }
+}
+
+impl Into<VType> for VSingleType {
+    fn into(self) -> VType {
+        VType { types: vec![self] }
+    }
+}