This MR finishes up all remaining Pre V1 goals

* add a posix exit() builtin
* improve separation of concerns regarding standard library structure

src/stl/control.rs

@@ -18,9 +18,10 @@
 use crate::eval::eval;
 use crate::error::{Traceback, start_trace};
 use crate::segment::{Ctr, Seg};
-use crate::sym::{SymTable, Symbol};
+use crate::sym::{SymTable, Symbol, ValueType, Args};
+use std::rc::Rc;
 
-pub const IF_DOCSTRING: &str =
+const IF_DOCSTRING: &str =
     "accepts three bodies, a condition, an unevaluated consequence, and an alternative consequence.
 If the condition is evaluated to true, the first consequence is evaluated.
 If the condition is evaluated to false, the second consequence is evaluated.
@@ -29,8 +30,7 @@ Otherwise, an error is thrown.
 example: (if my-state-switch
            (do-my-thing)
            (else-an-other-thing))";
-
-pub fn if_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
+fn if_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
     let cond: bool;
     match *ast.car {
         Ctr::Seg(ref cond_form) => {
@@ -119,7 +119,7 @@ pub fn if_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
     }
 }
 
-pub const LET_DOCSTRING: &str = "creates a stack of local variables for a sequence of operations.
+const LET_DOCSTRING: &str = "creates a stack of local variables for a sequence of operations.
 returns the result of the final operation.
 
 example: (let ((step1 'hello')
@@ -132,8 +132,7 @@ In this example step1, step2, and step3 are created sequentially.
 Then, the echo form is evaluated, printing 'hello-world'.
 Finally, the some-func form is evaluated.
 Since the call to some-func is the final form, its value is returned.";
-
-pub fn let_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
+fn let_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
     let mut localsyms = syms.clone();
     let mut locals = vec![];
     let locals_form: &Seg;
@@ -250,15 +249,14 @@ pub fn let_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
     Ok((*result).clone())
 }
 
-pub const WHILE_DOCSTRING: &str = "traverses a list of N un-evaluated forms.
+const WHILE_DOCSTRING: &str = "traverses a list of N un-evaluated forms.
 the first form is expected to evaluate to a boolean. if it evaluates to false, while will stop and return. Otherwise, while will evaluate each form in a loop.
 
 example: (while (check-my-state)
                 (do-thing-1 args)
                 (do-thing-2 args)
                 (edit-state my-state))";
-
-pub fn while_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
+fn while_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
     let eval_cond: &Seg;
     let outer_maybe: Seg;
     let eval_bodies_head: &Seg;
@@ -319,7 +317,7 @@ pub fn while_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback>
     Ok(*(result.unwrap()).clone())
 }
 
-pub const CIRCUIT_DOCSTRING: &str = "traverses a list of N un-evaluated forms.
+const CIRCUIT_DOCSTRING: &str = "traverses a list of N un-evaluated forms.
 evaluates each one until it stops. Circuit will stop when a form errors during evaluation.
 Circuit will also stop when a form does not evaluate to a boolean, or evaluates to false.
 
@@ -329,8 +327,7 @@ example: (circuit (eq? (do-operation) myresult)
                   (do-another-operation))
 
 in this example, do-another-operation will not be called";
-
-pub fn circuit_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
+fn circuit_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
     let mut cursor = 0;
     let mut err_trace = Traceback::new();
     let result = ast.circuit(&mut |form: &Ctr| -> bool {
@@ -383,3 +380,53 @@ pub fn circuit_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback
         Ok(Ctr::Bool(result))
     }
 }
+
+pub fn add_control_lib(syms: &mut SymTable) {
+    syms.insert(
+        "if".to_string(),
+        Symbol {
+            name: String::from("if"),
+            args: Args::Lazy(3),
+            conditional_branches: true,
+            docs: IF_DOCSTRING.to_string(),
+            value: ValueType::Internal(Rc::new(if_callback)),
+            ..Default::default()
+        },
+    );
+
+    syms.insert(
+        "let".to_string(),
+        Symbol {
+            name: String::from("let"),
+            args: Args::Infinite,
+            conditional_branches: true,
+            docs: LET_DOCSTRING.to_string(),
+            value: ValueType::Internal(Rc::new(let_callback)),
+            ..Default::default()
+        },
+    );
+
+    syms.insert(
+        "while".to_string(),
+        Symbol {
+            name: String::from("while"),
+            args: Args::Infinite,
+            conditional_branches: true,
+            docs: WHILE_DOCSTRING.to_string(),
+            value: ValueType::Internal(Rc::new(while_callback)),
+            ..Default::default()
+        },
+    );
+
+    syms.insert(
+        "circuit".to_string(),
+        Symbol {
+            name: String::from("circuit"),
+            args: Args::Infinite,
+            conditional_branches: true,
+            docs: CIRCUIT_DOCSTRING.to_string(),
+            value: ValueType::Internal(Rc::new(circuit_callback)),
+            ..Default::default()
+        },
+    );
+}