add missing doc comments

src/context/mod.rs

@@ -175,6 +175,7 @@ impl Context {
         })
     }
 
+    /// Get a snapshot of environment state for a list of symbols.
     pub fn close(&self, vars: Vec<&str>) -> Env {
         let mut out = Env::new();
 
@@ -187,6 +188,7 @@ impl Context {
         out
     }
 
+    /// Use definitions from a closure (or purge the existing ones)
     pub fn overlay_env(&mut self, env: Option<Env>) {
         self.overlay = env;
     }

src/context/write.rs

@@ -5,15 +5,18 @@ use super::Context;
 const PREALLOC_BUFFER: usize = 199;
 
 impl Context {
+    /// Start capturing printed content in a buffer.
     pub fn capture(&mut self) {
         self.out = Some(String::with_capacity(PREALLOC_BUFFER));
     }
 
+    /// Capture `display` and `write` statement output in a buffer.
     pub fn capturing(mut self) -> Self {
         self.capture();
         self
     }
 
+    /// Get the captured side-effect output.
     pub fn get_output(&mut self) -> Option<String> {
         self.out.take()
     }

src/sexp/mod.rs

@@ -137,6 +137,7 @@ impl SExp {
         }
     }
 
+    /// Make a basic (pure fuctional) procedure.
     pub fn proc<F>(f: F, name: Option<&str>) -> Self
     where
         F: Fn(Self) -> Result + 'static,
@@ -148,6 +149,7 @@ impl SExp {
         })
     }
 
+    /// Make a procedure that can mutate or query its execution context.
     pub fn ctx_proc<F>(f: F, name: Option<&str>) -> Self
     where
         F: Fn(Self, &mut Context) -> Result + 'static,