Add --no-add-history flag

Flag prevents the input stream from saving terms to ~/.scryer_history
when set. Use the flag when running tests to increase test isolation.

src/machine/args.rs

@@ -0,0 +1,16 @@
+use std::collections::BTreeSet;
+use std::env;
+
+#[derive(Debug)]
+pub struct MachineArgs {
+    pub add_history: bool,
+}
+
+impl MachineArgs {
+    pub fn new() -> Self {
+        let args: BTreeSet<String> = env::args().collect();
+        Self {
+            add_history: !args.contains("--no-add-history"),
+        }
+    }
+}

src/machine/mod.rs

@@ -1,3 +1,4 @@
+pub mod args;
 pub mod arithmetic_ops;
 pub mod attributed_variables;
 pub mod code_walker;
@@ -25,6 +26,7 @@ use crate::arithmetic::*;
 use crate::atom_table::*;
 use crate::forms::*;
 use crate::instructions::*;
+use crate::machine::args::*;
 use crate::machine::compile::*;
 use crate::machine::copier::*;
 use crate::machine::heap::*;
@@ -396,9 +398,10 @@ impl Machine {
     pub fn new() -> Self {
         use ref_thread_local::RefThreadLocal;
 
+        let args = MachineArgs::new();
         let mut machine_st = MachineState::new();
 
-        let user_input = Stream::stdin(&mut machine_st.arena);
+        let user_input = Stream::stdin(&mut machine_st.arena, args.add_history);
         let user_output = Stream::stdout(&mut machine_st.arena);
         let user_error = Stream::stderr(&mut machine_st.arena);
 

src/machine/streams.rs

@@ -426,9 +426,9 @@ impl Stream {
     }
 
     #[inline]
-    pub fn stdin(arena: &mut Arena) -> Stream {
+    pub fn stdin(arena: &mut Arena, add_history: bool) -> Stream {
         Stream::Readline(arena_alloc!(
-            StreamLayout::new(ReadlineStream::new("")),
+            StreamLayout::new(ReadlineStream::new("", add_history)),
             arena
         ))
     }

src/machine/system_calls.rs

@@ -4094,7 +4094,7 @@ impl Machine {
         match result {
             Ok(()) => Ok(()),
             Err(e) => {
-                self.user_input = input_stream(&mut self.machine_st.arena);
+                self.user_input.reset();
                 return Err(e);
             }
         }