diff --git a/README.md b/README.md
index bfc81ac..9845858 100644
--- a/README.md
+++ b/README.md
@@ -174,13 +174,14 @@ more date functions will have to follow.
 **lists**
 ```
 let list = ["foo", "bar", 1, 1.0]
-print(list[1])
+list[1]
 => "bar"
 ```
 No generic types (yet). A list can hold any type.
 * lists support appending with + 
 ```
-let list 2 = list + "baz"
+let list2 = list + "baz"
+=>["foo", "bar", 1, 1.0, "baz"]
 ```
 _note to self: implement adding 2 lists_
 
diff --git a/src/ast_compiler.rs b/src/ast_compiler.rs
index bc40a04..c04eed2 100644
--- a/src/ast_compiler.rs
+++ b/src/ast_compiler.rs
@@ -2,28 +2,30 @@ use crate::ast_compiler::Expression::{
     FieldGet, FunctionCall, ListGet, MapGet, NamedParameter, Stop, Variable,
 };
 use crate::errors::CompilerError::{
-    self, Expected, IncompatibleTypes, ParseError, TooManyParameters, TypeError,
-    UndeclaredVariable, UnexpectedIndent, UninitializedVariable,
+    self, Expected, ParseError, TooManyParameters, UndeclaredVariable, UnexpectedIndent,
+    UninitializedVariable,
 };
 use crate::errors::CompilerErrorAtLine;
+use crate::symbol_builder::{Symbol, calculate_type, infer_type};
 use crate::tokens::TokenType::{
     Bang, Bool, Char, Colon, DateTime, Dot, Eof, Eol, Equal, F32, F64, False, FloatingPoint, Fn,
     Greater, GreaterEqual, GreaterGreater, I32, I64, Identifier, Indent, Integer, LeftBrace,
     LeftBracket, LeftParen, Less, LessEqual, LessLess, Let, ListType, MapType, Minus, Object, Plus,
     Print, RightBrace, RightBracket, RightParen, SignedInteger, SingleRightArrow, Slash, Star,
-    StringType, True, U32, U64, UnsignedInteger,
+    StringType, True, U32, U64, Unknown, UnsignedInteger,
 };
 use crate::tokens::{Token, TokenType};
 use crate::value::Value;
 use log::debug;
-use tokio_postgres::fallible_iterator::FallibleIterator;
+use std::collections::HashMap;
 
 pub fn compile(
     path: Option<&str>,
     tokens: Vec<Token>,
+    symbol_table: &mut HashMap<String, Symbol>,
 ) -> Result<Vec<Statement>, CompilerErrorAtLine> {
     let mut compiler = AstCompiler::new(path.unwrap_or(""), tokens);
-    compiler.compile_tokens()
+    compiler.compile_tokens(symbol_table)
 }
 
 #[derive(Debug, Clone)]
@@ -55,17 +57,23 @@ impl AstCompiler {
         self.current = 0;
     }
 
-    fn compile_tokens(&mut self) -> Result<Vec<Statement>, CompilerErrorAtLine> {
+    fn compile_tokens(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Vec<Statement>, CompilerErrorAtLine> {
         self.reset();
-        self.compile()
+        self.compile(symbol_table)
     }
 
-    fn compile(&mut self) -> Result<Vec<Statement>, CompilerErrorAtLine> {
+    fn compile(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Vec<Statement>, CompilerErrorAtLine> {
         self.current_line();
         if !self.had_error {
             let mut statements = vec![];
             while !self.is_at_end() {
-                let statement = self.indent()?;
+                let statement = self.indent(symbol_table)?;
                 if let Some(statement) = statement {
                     statements.push(statement);
                 } else {
@@ -83,7 +91,10 @@ impl AstCompiler {
         CompilerErrorAtLine::raise(error, self.current_line())
     }
 
-    fn indent(&mut self) -> Result<Option<Statement>, CompilerErrorAtLine> {
+    fn indent(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Option<Statement>, CompilerErrorAtLine> {
         let expected_indent = *self.indent.last().unwrap();
         // skip empty lines
         while self.check(Eol) {
@@ -101,39 +112,48 @@ impl AstCompiler {
             self.indent.pop();
             return Ok(None);
         } else {
-            Ok(Some(self.declaration()?))
+            Ok(Some(self.declaration(symbol_table)?))
         }
     }
 
-    fn declaration(&mut self) -> Result<Statement, CompilerErrorAtLine> {
+    fn declaration(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Statement, CompilerErrorAtLine> {
         if self.match_token(vec![Fn]) {
-            self.function_declaration()
+            self.function_declaration(symbol_table)
         } else if self.match_token(vec![Let]) {
-            self.let_declaration()
+            self.let_declaration(symbol_table)
         } else if self.match_token(vec![Object]) {
             self.object_declaration()
         } else if self.match_token(vec![TokenType::Pipe]) {
-            self.guard_declaration()
+            self.guard_declaration(symbol_table)
         } else {
-            self.statement()
+            self.statement(symbol_table)
         }
     }
 
     //  | /. -> service.get_all()
     //  | /{uuid} -> service.get(uuid)?
     //  | ?{query.firstname} -> service.get_by_firstname(fname)?
-    fn guard_declaration(&mut self) -> Result<Statement, CompilerErrorAtLine> {
-        let if_expr = self.guard_if_expr()?;
-        let then_expr = self.expression()?;
+    fn guard_declaration(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Statement, CompilerErrorAtLine> {
+        let if_expr = self.guard_if_expr(symbol_table)?;
+        let then_expr = self.expression(symbol_table)?;
         Ok(Statement::GuardStatement { if_expr, then_expr })
     }
 
-    fn guard_if_expr(&mut self) -> Result<Expression, CompilerErrorAtLine> {
+    fn guard_if_expr(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
         while !self.check(SingleRightArrow) {
             if self.match_token(vec![Slash]) {
                 return self.path_guard_expr();
             } else if self.match_token(vec![TokenType::Question]) {
-                return self.query_guard_expr();
+                return self.query_guard_expr(symbol_table);
             } else {
                 return Err(self.raise(Expected("-> or ?")));
             }
@@ -143,9 +163,12 @@ impl AstCompiler {
         })
     }
 
-    fn query_guard_expr(&mut self) -> Result<Expression, CompilerErrorAtLine> {
+    fn query_guard_expr(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
         if self.match_token(vec![LeftBrace]) {
-            let query_params = self.expression()?;
+            let query_params = self.expression(symbol_table)?;
             self.consume(RightBrace, Expected("'}' after guard expression."))?;
             Ok(query_params)
         } else {
@@ -211,7 +234,10 @@ impl AstCompiler {
         })
     }
 
-    fn function_declaration(&mut self) -> Result<Statement, CompilerErrorAtLine> {
+    fn function_declaration(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Statement, CompilerErrorAtLine> {
         let name_token = self.consume(Identifier, Expected("function name."))?;
         self.consume(LeftParen, Expected("'(' after function name."))?;
         let mut parameters = vec![];
@@ -246,7 +272,7 @@ impl AstCompiler {
         let current_indent = self.indent.last().unwrap();
         self.indent.push(current_indent + 1);
 
-        let body = self.compile()?;
+        let body = self.compile(symbol_table)?;
 
         let function = Function {
             name: name_token.clone(),
@@ -258,7 +284,10 @@ impl AstCompiler {
         Ok(Statement::FunctionStmt { function })
     }
 
-    fn let_declaration(&mut self) -> Result<Statement, CompilerErrorAtLine> {
+    fn let_declaration(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Statement, CompilerErrorAtLine> {
         if self.peek().token_type.is_type() {
             return Err(self.raise(CompilerError::KeywordNotAllowedAsIdentifier(
                 self.peek().token_type.clone(),
@@ -274,25 +303,24 @@ impl AstCompiler {
         };
 
         if self.match_token(vec![Equal]) {
-            let initializer = self.expression()?;
+            let initializer = self.expression(symbol_table)?;
+            let declared_type = declared_type.unwrap_or(Unknown);
+            let inferred_type = initializer.infer_type();
+            let var_type =
+                calculate_type(&declared_type, &inferred_type).map_err(|e| self.raise(e))?;
+            symbol_table.insert(
+                name_token.lexeme.clone(),
+                Symbol::Variable {
+                    name: name_token.lexeme.clone(),
+                    var_type: var_type.clone(),
+                },
+            );
+
             self.consume(Eol, Expected("end of line after initializer."))?;
 
-            // let inferred_type = initializer.infer_type();
-            // let var_type = match calculate_type(declared_type, inferred_type) {
-            //     Ok(var_type) => var_type,
-            //     Err(e) => {
-            //         self.had_error = true;
-            //         return Err(self.raise(TypeError(Box::new(e))));
-            //     }
-            // };
-            // self.vars.push(Variable {
-            //     name: name_token.lexeme.to_string(),
-            //     var_type,
-            //     line: name_token.line,
-            // });
             Ok(Statement::VarStmt {
                 name: name_token,
-                var_type: declared_type.unwrap_or(TokenType::Unknown),
+                var_type,
                 initializer,
             })
         } else {
@@ -300,90 +328,141 @@ impl AstCompiler {
         }
     }
 
-    fn statement(&mut self) -> Result<Statement, CompilerErrorAtLine> {
+    fn statement(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Statement, CompilerErrorAtLine> {
         if self.match_token(vec![Print]) {
-            self.print_statement()
+            self.print_statement(symbol_table)
         } else {
-            self.expr_statement()
+            self.expr_statement(symbol_table)
         }
     }
 
-    fn print_statement(&mut self) -> Result<Statement, CompilerErrorAtLine> {
-        let expr = self.expression()?;
+    fn print_statement(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Statement, CompilerErrorAtLine> {
+        let expr = self.expression(symbol_table)?;
         self.consume(Eol, Expected("end of line after print statement."))?;
         Ok(Statement::PrintStmt { value: expr })
     }
 
-    fn expr_statement(&mut self) -> Result<Statement, CompilerErrorAtLine> {
-        let expr = self.expression()?;
+    fn expr_statement(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Statement, CompilerErrorAtLine> {
+        let expr = self.expression(symbol_table)?;
         if !self.is_at_end() {
             self.consume(Eol, Expected("end of line after expression."))?;
         }
         Ok(Statement::ExpressionStmt { expression: expr })
     }
 
-    fn expression(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        self.or()
+    fn expression(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        self.or(symbol_table)
     }
 
-    fn or(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.and()?;
-        self.binary(vec![TokenType::LogicalOr], expr)
+    fn or(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.and(symbol_table)?;
+        self.binary(vec![TokenType::LogicalOr], expr, symbol_table)
     }
 
-    fn and(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.bit_and()?;
-        self.binary(vec![TokenType::LogicalAnd], expr)
+    fn and(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.bit_and(symbol_table)?;
+        self.binary(vec![TokenType::LogicalAnd], expr, symbol_table)
     }
 
-    fn bit_and(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.bit_or()?;
-        self.binary(vec![TokenType::BitAnd], expr)
+    fn bit_and(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.bit_or(symbol_table)?;
+        self.binary(vec![TokenType::BitAnd], expr, symbol_table)
     }
 
-    fn bit_or(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.bit_xor()?;
-        self.binary(vec![TokenType::Pipe], expr)
+    fn bit_or(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.bit_xor(symbol_table)?;
+        self.binary(vec![TokenType::Pipe], expr, symbol_table)
     }
 
-    fn bit_xor(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.equality()?;
-        self.binary(vec![TokenType::BitXor], expr)
+    fn bit_xor(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.equality(symbol_table)?;
+        self.binary(vec![TokenType::BitXor], expr, symbol_table)
     }
 
-    fn equality(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.comparison()?;
-        self.binary(vec![TokenType::EqualEqual, TokenType::BangEqual], expr)
+    fn equality(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.comparison(symbol_table)?;
+        self.binary(
+            vec![TokenType::EqualEqual, TokenType::BangEqual],
+            expr,
+            symbol_table,
+        )
     }
 
-    fn comparison(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.bitshift()?;
-        self.binary(vec![Greater, GreaterEqual, Less, LessEqual], expr)
+    fn comparison(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.bitshift(symbol_table)?;
+        self.binary(
+            vec![Greater, GreaterEqual, Less, LessEqual],
+            expr,
+            symbol_table,
+        )
     }
 
-    fn bitshift(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.term()?;
-        self.binary(vec![GreaterGreater, LessLess], expr)
+    fn bitshift(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.term(symbol_table)?;
+        self.binary(vec![GreaterGreater, LessLess], expr, symbol_table)
     }
 
-    fn term(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.factor()?;
-        self.binary(vec![Minus, Plus], expr)
+    fn term(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.factor(symbol_table)?;
+        self.binary(vec![Minus, Plus], expr, symbol_table)
     }
 
-    fn factor(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.unary()?;
-        self.binary(vec![Slash, Star], expr)
+    fn factor(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.unary(symbol_table)?;
+        self.binary(vec![Slash, Star], expr, symbol_table)
     }
 
     fn binary(
         &mut self,
         types: Vec<TokenType>,
         mut expr: Expression,
+        symbol_table: &mut HashMap<String, Symbol>,
     ) -> Result<Expression, CompilerErrorAtLine> {
         while self.match_token(types.clone()) {
             let operator = self.previous().clone();
-            let right = self.comparison()?;
+            let right = self.comparison(symbol_table)?;
             expr = Expression::Binary {
                 line: operator.line,
                 left: Box::new(expr),
@@ -394,33 +473,38 @@ impl AstCompiler {
         Ok(expr)
     }
 
-    fn unary(&mut self) -> Result<Expression, CompilerErrorAtLine> {
+    fn unary(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
         if self.match_token(vec![Bang, Minus]) {
             let operator = self.previous().clone();
-            let right = self.unary()?;
+            let right = self.unary(symbol_table)?;
             Ok(Expression::Unary {
                 line: self.peek().line,
                 operator,
                 right: Box::new(right),
             })
         } else {
-            let expr = self.get();
+            let expr = self.get(symbol_table);
             expr
         }
     }
 
-    fn get(&mut self) -> Result<Expression, CompilerErrorAtLine> {
-        let expr = self.primary()?;
+    fn get(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let expr = self.primary(symbol_table)?;
 
         if self.match_token(vec![LeftParen]) {
             let name = self.peek().clone();
             self.advance();
-            self.function_call(name)
+            self.function_call(name, symbol_table)
         } else if self.match_token(vec![LeftBracket]) {
-            let name = self.peek().clone();
-            self.advance();
-            self.index(expr, name)
-        } else if self.match_token(vec![Dot]){
+            let index = self.expression(symbol_table)?;
+            self.index(expr, index)
+        } else if self.match_token(vec![Dot]) {
             let name = self.peek().clone();
             self.advance();
             self.field(expr, name)
@@ -432,19 +516,27 @@ impl AstCompiler {
     fn index(
         &mut self,
         operand: Expression,
-        index: Token,
+        index: Expression,
     ) -> Result<Expression, CompilerErrorAtLine> {
-        let get = (match operand {
+        let get = (match &operand {
             Expression::Map { .. } => MapGet {
-                key: index.lexeme.clone(),
+                key: Box::new(index),
             },
             Expression::List { .. } => ListGet {
                 list: Box::new(operand),
-                index: index.lexeme.clone().parse().map_err(|_| {
-                    self.raise(CompilerError::IllegalTypeToIndex(index.lexeme.clone()))
-                })?,
+                index: Box::new(index),
             },
-            _ => return Err(self.raise(CompilerError::IllegalTypeToIndex("".to_string()))),
+            Variable { var_type, .. } => {
+                if var_type == &ListType {
+                    ListGet {
+                        list: Box::new(operand),
+                        index: Box::new(index),
+                    }
+                } else {
+                    return Err(self.raise(CompilerError::IllegalTypeToIndex(var_type.to_string())));
+                }
+            }
+            _ => return Err(self.raise(CompilerError::IllegalTypeToIndex("Unknown".to_string()))),
         });
         self.consume(RightBracket, Expected("']' after index."))?;
         Ok(get)
@@ -461,12 +553,15 @@ impl AstCompiler {
         })
     }
 
-    fn primary(&mut self) -> Result<Expression, CompilerErrorAtLine> {
+    fn primary(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
         debug!("primary {:?}", self.peek());
         Ok(if self.match_token(vec![LeftBracket]) {
-            self.list()?
+            self.list(symbol_table)?
         } else if self.match_token(vec![LeftBrace]) {
-            self.map()?
+            self.map(symbol_table)?
         } else if self.match_token(vec![False]) {
             Expression::Literal {
                 line: self.peek().line,
@@ -545,7 +640,7 @@ impl AstCompiler {
                 ),
             }
         } else if self.match_token(vec![LeftParen]) {
-            let expr = self.expression()?;
+            let expr = self.expression(symbol_table)?;
             self.consume(RightParen, Expected("')' after expression."))?;
             Expression::Grouping {
                 line: self.peek().line,
@@ -556,9 +651,9 @@ impl AstCompiler {
             debug!("{:?}", token);
             // function call?
             if self.match_token(vec![LeftParen]) {
-                self.function_call(token.clone())?
+                self.function_call(token.clone(), symbol_table)?
             } else if self.match_token(vec![Colon]) {
-                self.named_parameter(&token)?
+                self.named_parameter(&token, symbol_table)?
             } else {
                 // } else if self.check(Dot) {
                 // chain of variable or function lookups?
@@ -586,13 +681,17 @@ impl AstCompiler {
                 // }
                 // } else {
                 // none of the above, must be a variable lookup
-                self.variable_lookup(&token)?
+                self.variable_lookup(&token, symbol_table)?
             }
         })
     }
 
-    fn named_parameter(&mut self, name: &Token) -> Result<Expression, CompilerErrorAtLine> {
-        let value = self.expression()?;
+    fn named_parameter(
+        &mut self,
+        name: &Token,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let value = self.expression(symbol_table)?;
         let line = name.line;
         Ok(NamedParameter {
             name: name.clone(),
@@ -601,10 +700,13 @@ impl AstCompiler {
         })
     }
 
-    fn list(&mut self) -> Result<Expression, CompilerErrorAtLine> {
+    fn list(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
         let mut list = vec![];
         while !self.match_token(vec![RightBracket]) {
-            list.push(self.expression()?);
+            list.push(self.expression(symbol_table)?);
             if self.peek().token_type == TokenType::Comma {
                 self.advance();
             } else {
@@ -619,12 +721,15 @@ impl AstCompiler {
         })
     }
 
-    fn map(&mut self) -> Result<Expression, CompilerErrorAtLine> {
+    fn map(
+        &mut self,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
         let mut entries = vec![];
         while !self.match_token(vec![RightBrace]) {
-            let key = self.expression()?;
+            let key = self.expression(symbol_table)?;
             self.consume(Colon, Expected("':' after map key."))?;
-            let value = self.expression()?;
+            let value = self.expression(symbol_table)?;
             entries.push((key, value));
             if self.peek().token_type == TokenType::Comma {
                 self.advance();
@@ -640,21 +745,35 @@ impl AstCompiler {
         })
     }
 
-    fn variable_lookup(&mut self, name: &Token) -> Result<Expression, CompilerErrorAtLine> {
+    fn variable_lookup(
+        &mut self,
+        name: &Token,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
+        let var = symbol_table.get(&name.lexeme);
+        let var_type = if let Some(Symbol::Variable { var_type, .. }) = var {
+            var_type
+        } else {
+            &Unknown
+        };
         Ok(Variable {
             name: name.lexeme.to_string(),
-            var_type: TokenType::Unknown,
+            var_type: var_type.clone(),
             line: name.line,
         })
     }
 
-    fn function_call(&mut self, name: Token) -> Result<Expression, CompilerErrorAtLine> {
+    fn function_call(
+        &mut self,
+        name: Token,
+        symbol_table: &mut HashMap<String, Symbol>,
+    ) -> Result<Expression, CompilerErrorAtLine> {
         let mut arguments = vec![];
         while !self.match_token(vec![RightParen]) {
             if arguments.len() >= 25 {
                 return Err(self.raise(TooManyParameters));
             }
-            let arg = self.expression()?;
+            let arg = self.expression(symbol_table)?;
             arguments.push(arg);
             if self.peek().token_type == TokenType::Comma {
                 self.advance();
@@ -826,11 +945,11 @@ pub enum Expression {
         value: Box<Expression>,
     },
     MapGet {
-        key: String,
+        key: Box<Expression>,
     },
     ListGet {
         list: Box<Expression>,
-        index: usize,
+        index: Box<Expression>,
     },
     FieldGet {
         field: String,
@@ -857,20 +976,86 @@ impl Expression {
         }
     }
 
-    // pub fn get_type(&self) -> &str {
-    //     match self {
-    //         Expression::Binary { .. } => "binary",
-    //         Expression::Unary { .. } => TokenType::Unknown,
-    //         Expression::Grouping { .. } => TokenType::Unknown,
-    //         Expression::Literal { literaltype, .. } => literaltype.clone(),
-    //         Expression::List { literaltype, .. } => literaltype.clone(),
-    //         Expression::Map { literaltype, .. } => literaltype.clone(),
-    //         Expression::Variable { var_type, .. } => var_type.clone(),
-    //         Expression::FunctionCall { .. } => TokenType::Unknown,
-    //         Expression::Stop { .. } => TokenType::Unknown,
-    //         Expression::NamedParameter { .. } => TokenType::Unknown,
-    //         Expression::MapGet { .. } => TokenType::Unknown,
-    //         Expression::ListGet { .. } => TokenType::Unknown,
-    //     }
-    // }
+    pub fn infer_type(&self) -> TokenType {
+        match self {
+            Expression::Binary {
+                left,
+                operator,
+                right,
+                ..
+            } => {
+                let left_type = left.infer_type();
+                let right_type = right.infer_type();
+                if vec![Greater, Less, GreaterEqual, LessEqual].contains(&operator.token_type) {
+                    Bool
+                } else if left_type == right_type {
+                    // map to determined numeric type if yet undetermined (32 or 64 bits)
+                    match left_type {
+                        FloatingPoint => F64,
+                        Integer => I64,
+                        _ => left_type,
+                    }
+                } else {
+                    if let Plus = operator.token_type {
+                        // includes string concatenation with numbers
+                        // followed by type coercion to 64 bits for numeric types
+                        debug!("coerce {} : {}", left_type, right_type);
+                        match (left_type, right_type) {
+                            (_, StringType) => StringType,
+                            (StringType, _) => StringType,
+                            (FloatingPoint, _) => F64,
+                            (Integer, FloatingPoint) => F64,
+                            (Integer, _) => I64,
+                            (I64, Integer) => I64,
+                            (F64, _) => F64,
+                            (U64, U32) => U64,
+                            (I64, I32) => I64,
+                            // could add a date and a duration. future work
+                            // could add a List and a value. also future work
+                            // could add a Map and a tuple. Will I add tuple types? Future work!
+                            _ => panic!("Unexpected coercion"),
+                        }
+                        // could have done some fall through here, but this will fail less gracefully,
+                        // so if my thinking is wrong or incomplete it will panic
+                    } else {
+                        // type coercion to 64 bits for numeric types
+                        debug!("coerce {} : {}", left_type, right_type);
+                        match (left_type, right_type) {
+                            (FloatingPoint, _) => F64,
+                            (Integer, FloatingPoint) => F64,
+                            (Integer, I64) => I64,
+                            (I64, FloatingPoint) => F64,
+                            (F64, _) => F64,
+                            (U64, U32) => U64,
+                            (I64, I32) => I64,
+                            (I64, Integer) => I64,
+                            _ => panic!("Unexpected coercion"),
+                        }
+                    }
+                }
+            }
+            Expression::Grouping { expression, .. } => expression.infer_type(),
+            Expression::Literal { literaltype, .. } => literaltype.clone(),
+            Expression::List { literaltype, .. } => literaltype.clone(),
+            Expression::Map { literaltype, .. } => literaltype.clone(),
+            Expression::Unary {
+                right, operator, ..
+            } => {
+                let literal_type = right.infer_type();
+                if literal_type == Integer && operator.token_type == Minus {
+                    SignedInteger
+                } else {
+                    UnsignedInteger
+                }
+            }
+            Expression::Variable { var_type, .. } => var_type.clone(),
+            Expression::Stop { .. } => TokenType::Unknown,
+            // Expression::PathMatch { .. } => TokenType::Unknown,
+            Expression::NamedParameter { .. } => TokenType::Unknown,
+            Expression::ListGet { .. } => TokenType::Unknown,
+            Expression::MapGet { .. } => TokenType::Unknown,
+            Expression::FieldGet { .. } => TokenType::Unknown,
+            FunctionCall { .. } => TokenType::Unknown,
+        }
+    }
 }
diff --git a/src/bytecode_compiler.rs b/src/bytecode_compiler.rs
index 64b0f5d..434189f 100644
--- a/src/bytecode_compiler.rs
+++ b/src/bytecode_compiler.rs
@@ -110,12 +110,11 @@ impl Compiler {
                 let var = symbols.get(name);
                 if let Some(Symbol::Variable {
                     var_type,
-                    initializer,
                     ..
                 }) = var
                 {
                     let inferred_type = infer_type(initializer, symbols);
-                    let calculated_type = calculate_type(var_type, &inferred_type, symbols)
+                    let calculated_type = calculate_type(var_type, &inferred_type)
                         .map_err(|e| CompilerErrorAtLine::raise(e, statement.line()))?;
                     if var_type != &Unknown && var_type != &calculated_type {
                         return Err(CompilerErrorAtLine::raise(
@@ -298,8 +297,8 @@ impl Compiler {
             NamedParameter { .. } => {}
             Expression::ListGet { index, list} => {
                 self.compile_expression(namespace, list, symbols, registry)?;
+                self.compile_expression(namespace, index, symbols, registry)?;
                 self.emit_byte(OP_LIST_GET);
-                self.emit_bytes((index >> 16) as u16, *index as u16);
             }
             Expression::MapGet { .. } => {}
             Expression::FieldGet { .. } => {}
diff --git a/src/lib.rs b/src/lib.rs
index c76c01d..7ba6a6e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -33,14 +33,18 @@ pub fn compile_sourcedir(source_dir: &str) -> Result<HashMap<String, Chunk>, Cru
             print!("-- Compiling {} -- ", path);
             let source = fs::read_to_string(path).map_err(map_underlying())?;
             let tokens = scan(&source)?;
-            match ast_compiler::compile(Some(&path), tokens) {
+            let mut symbol_table = HashMap::new();
+            match ast_compiler::compile(Some(&path), tokens, &mut symbol_table) {
                 Ok(statements) => {
                     let path = path.strip_prefix(source_dir).unwrap().replace(".crud", "");
 
-                    let mut symbol_table = HashMap::new();
                     symbol_builder::build(&path, &statements, &mut symbol_table);
-
-                    bytecode_compiler::compile(Some(&path), &statements, &symbol_table, &mut registry)?;
+                    bytecode_compiler::compile(
+                        Some(&path),
+                        &statements,
+                        &symbol_table,
+                        &mut registry,
+                    )?;
                 }
                 Err(e) => {
                     println!("{}", e);
@@ -59,8 +63,8 @@ pub fn map_underlying() -> fn(std::io::Error) -> CrudLangError {
 
 pub fn recompile(src: &str, registry: &mut HashMap<String, Chunk>) -> Result<(), CrudLangError> {
     let tokens = scan(src)?;
-    let ast = ast_compiler::compile(None, tokens)?;
     let mut symbol_table = HashMap::new();
+    let ast = ast_compiler::compile(None, tokens, &mut symbol_table)?;
     symbol_builder::build("", &ast, &mut symbol_table);
     bytecode_compiler::compile(None, &ast, &symbol_table, registry)?;
     Ok(())
@@ -69,8 +73,8 @@ pub fn recompile(src: &str, registry: &mut HashMap<String, Chunk>) -> Result<(),
 pub fn compile(src: &str) -> Result<HashMap<String, Chunk>, CrudLangError> {
     let tokens = scan(src)?;
     let mut registry = HashMap::new();
-    let ast = ast_compiler::compile(None, tokens)?;
     let mut symbol_table = HashMap::new();
+    let ast = ast_compiler::compile(None, tokens, &mut symbol_table)?;
     symbol_builder::build("", &ast, &mut symbol_table);
     bytecode_compiler::compile(None, &ast, &symbol_table, &mut registry)?;
     Ok(registry)
@@ -78,8 +82,8 @@ pub fn compile(src: &str) -> Result<HashMap<String, Chunk>, CrudLangError> {
 
 pub(crate) fn run(src: &str) -> Result<Value, CrudLangError> {
     let tokens = scan(src)?;
-    let ast = ast_compiler::compile(None, tokens)?;
     let mut symbol_table = HashMap::new();
+    let ast = ast_compiler::compile(None, tokens, &mut symbol_table)?;
     symbol_builder::build("", &ast, &mut symbol_table);
     let mut registry = HashMap::new();
     bytecode_compiler::compile(None, &ast, &symbol_table, &mut registry)?;
diff --git a/src/symbol_builder.rs b/src/symbol_builder.rs
index 646f153..340bd7e 100644
--- a/src/symbol_builder.rs
+++ b/src/symbol_builder.rs
@@ -1,8 +1,12 @@
 use crate::ast_compiler::{Expression, Parameter, Statement};
 use crate::errors::CompilerError;
 use crate::errors::CompilerError::{IncompatibleTypes, TypeError};
+use crate::tokens::TokenType::{
+    Bool, DateTime, F32, F64, FloatingPoint, Greater, GreaterEqual, I32, I64, Integer, Less,
+    LessEqual, ListType, MapType, Minus, Object, Plus, SignedInteger, StringType, U32, U64,
+    Unknown, UnsignedInteger,
+};
 use crate::tokens::{Token, TokenType};
-use crate::tokens::TokenType::{Bool, F32, F64, FloatingPoint, Greater, GreaterEqual, I32, I64, Integer, Less, LessEqual, ListType, MapType, Minus, Object, Plus, SignedInteger, StringType, U32, U64, Unknown, UnsignedInteger, DateTime};
 use log::debug;
 use std::collections::HashMap;
 
@@ -16,7 +20,6 @@ pub enum Symbol {
     Variable {
         name: String,
         var_type: TokenType,
-        initializer: Expression,
     },
     Object {
         name: String,
@@ -40,15 +43,17 @@ pub fn build(path: &str, ast: &[Statement], symbols: &mut HashMap<String, Symbol
                 var_type,
                 initializer,
             } => {
-
-                symbols.insert(
-                    make_qname(path, name),
-                    Symbol::Variable {
-                        name: name.lexeme.to_string(),
-                        var_type: var_type.clone(),
-                        initializer: initializer.clone(),
-                    },
-                );
+                let key = make_qname(path, name);
+                if !symbols.contains_key(&key) {
+                    // surely there's a better way to do this?
+                    symbols.insert(
+                        key,
+                        Symbol::Variable {
+                            name: name.lexeme.to_string(),
+                            var_type: var_type.clone(),
+                        },
+                    );
+                }
             }
             Statement::FunctionStmt { function } => {
                 symbols.insert(
@@ -88,7 +93,7 @@ pub fn _add_types(
                 initializer,
             } => {
                 let inferred_type = infer_type(initializer, symbols);
-                let calculated_type = calculate_type(var_type, &inferred_type, symbols)?;
+                let calculated_type = calculate_type(var_type, &inferred_type)?;
                 let entry = symbols.get_mut(&format!("{}.{}", path, name.lexeme));
                 if let Some(Symbol::Variable { var_type, .. }) = entry {
                     *var_type = calculated_type;
@@ -103,7 +108,6 @@ pub fn _add_types(
 pub fn calculate_type(
     declared_type: &TokenType,
     inferred_type: &TokenType,
-    _symbols: &HashMap<String, Symbol>,
 ) -> Result<TokenType, CompilerError> {
     Ok(if declared_type != &Unknown {
         if declared_type != inferred_type {
@@ -118,6 +122,7 @@ pub fn calculate_type(
                 (F64, FloatingPoint) => F64,
                 (U64, I64) => U64,
                 (U64, I32) => U64,
+                (I64, Integer) => I64,
                 (StringType, _) => StringType, // meh, this all needs rigorous testing. Update: this is in progress
                 _ => {
                     return Err(IncompatibleTypes(
diff --git a/src/value.rs b/src/value.rs
index 387ccaf..34ceb67 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -57,6 +57,18 @@ impl Value {
         }
     }
 
+    pub fn cast_usize(self) -> Result<usize, ValueError> {
+        match self {
+            Value::U32(v) => Ok(v as usize),
+            Value::U64(v) => Ok(v as usize),
+            Value::I32(v) => Ok(v as usize),
+            Value::I64(v) => Ok(v as usize),
+            Value::F32(v) => Ok(v as usize),
+            Value::F64(v) => Ok(v as usize),
+            _ => Err(ValueError::IllegalCast),
+        }
+    }
+
     pub fn cast_i32(self) -> Result<Self, ValueError> {
         match self {
             Value::U32(v) => Ok(Value::I32(v as i32)),
@@ -229,7 +241,7 @@ impl Add<&Value> for &Value {
                 (Value::String(s), Value::Bool(b)) => Ok(Value::String(format!("{}{}", s, b))),
                 (Value::String(s), Value::Char(c)) => Ok(Value::String(format!("{}{}", s, c))),
                 (Value::String(s1), Value::String(s2)) => {
-                    let mut s = String::with_capacity(s1.len()+s2.len());
+                    let mut s = String::with_capacity(s1.len() + s2.len());
                     s.push_str(s1.as_str());
                     s.push_str(s2.as_str());
                     Ok(Value::String(s))
diff --git a/src/vm.rs b/src/vm.rs
index fab689a..df76563 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -3,11 +3,11 @@ use crate::errors::RuntimeError::Something;
 use crate::errors::{RuntimeError, ValueError};
 use crate::tokens::TokenType;
 use crate::value::Value;
-use axum::http::{Uri};
+use arc_swap::Guard;
+use axum::http::Uri;
+use reqwest::get;
 use std::collections::HashMap;
 use std::sync::Arc;
-use arc_swap::Guard;
-use reqwest::get;
 use tracing::debug;
 
 pub struct Vm {
@@ -18,7 +18,10 @@ pub struct Vm {
     registry: Arc<HashMap<String, Chunk>>,
 }
 
-pub fn interpret(registry: Guard<Arc<HashMap<String, Chunk>>>, function: &str) -> Result<Value, RuntimeError> {
+pub fn interpret(
+    registry: Guard<Arc<HashMap<String, Chunk>>>,
+    function: &str,
+) -> Result<Value, RuntimeError> {
     let chunk = registry.get(function).unwrap().clone();
     // for (key,value) in registry.iter() {
     //     println!("{}", key);
@@ -191,12 +194,10 @@ impl Vm {
                     self.push(value.clone()); // not happy , take ownership, no clone
                 }
                 OP_LIST_GET => {
-                    let index_high = self.read(chunk);
-                    let index_low = self.read(chunk);
-                    let index = (index_high <<16) + index_low;
+                    let index = self.pop();
                     let list = self.pop();
                     if let Value::List(list) = list {
-                        self.push(list.get(index).cloned().unwrap())
+                        self.push(list.get(index.cast_usize()?).cloned().unwrap())
                     }
                 }
                 OP_CALL => {
@@ -211,7 +212,9 @@ impl Vm {
                     args.reverse();
 
                     let function_name = chunk.constants[function_name_index].to_string();
-                    let function_chunk = self.registry.get(&function_name)
+                    let function_chunk = self
+                        .registry
+                        .get(&function_name)
                         .or_else(|| self.registry.get(&format!("{}/{}", context, function_name)));
                     if function_chunk.is_none() {
                         return Err(RuntimeError::FunctionNotFound(function_name));