implementations for quote and eval

src/stl/decl.rs

@@ -20,6 +20,26 @@ use crate::segment::{Ctr, Seg};
 use crate::sym::{Args, SymTable, Symbol, UserFn, ValueType};
 use std::env;
 
+pub const QUOTE_DOCSTRING: &str = "takes a single unevaluated tree and returns it as it is: unevaluated.";
+
+pub fn quote_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
+    if ast.len() > 1 {
+        Err("do not quote more than one thing at a time".to_string())
+    } else {
+        Ok(Ctr::Seg(ast.clone()))
+    }
+}
+
+pub const EVAL_DOCSTRING: &str = "takes an unevaluated argument and evaluates it.";
+
+pub fn eval_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
+    if ast.len() > 1 {
+        Err("do not quote more than one thing at a time".to_string())
+    } else {
+        Ok(*eval(ast, syms)?.clone())
+    }
+}
+
 pub const HELP_DOCSTRING: &str = "prints help text for a given symbol. Expects only one argument.";
 
 pub fn help_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {