Implemented print as ? -> ()

5 files changed, 12 insertions, 0 deletions

diff --git a/src/parse/parsetree.rs b/src/parse/parsetree.rs
index 75758dc..28e5044 100644
--- a/src/parse/parsetree.rs
+++ b/src/parse/parsetree.rs
@@ -113,6 +113,7 @@ fn tokens_to_ast_inner(
             Some(Sym(s)) if s == "false"  => Ok(Atom(False)),
 	    Some(Sym(s)) if s == "quote"  => Ok(Atom(Quote)),
 	    Some(Sym(s)) if s == "vector" => Ok(Atom(Vector)),
+	    Some(Sym(s)) if s == "print" => Ok(Atom(Print)),
 	    Some(Sym(s)) if s == "let"    => Ok(Atom(Let)),
 	    Some(Sym(s))                  => Ok(Atom(Var(s))),
 	    Some(ParClose) => break,
diff --git a/src/sexp/display.rs b/src/sexp/display.rs
index c3db144..a978f61 100644
--- a/src/sexp/display.rs
+++ b/src/sexp/display.rs
@@ -27,6 +27,7 @@ impl fmt::Display for SLeaf {
             Var(s) => s.to_string(),
             Quote  => "quote".to_string(),
             Vector => "vector".to_string(),
+	    Print  => "print".to_string(),
             Let    => "let".to_string(),
             Nil    => "()".to_string(),
         })
@@ -40,6 +41,7 @@ impl fmt::Display for SExp {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Atom(leaf) => write!(f, "{}", leaf.to_string()),
+	    SCons(a, b) if **b == Atom(Nil) => (*a).fmt(f),
             SCons(a, b) =>
                 write!(
                     f,
diff --git a/src/sexp/mod.rs b/src/sexp/mod.rs
index 7aa517b..296553f 100644
--- a/src/sexp/mod.rs
+++ b/src/sexp/mod.rs
@@ -33,6 +33,8 @@ pub enum SLeaf {
 
     Let,
 
+    Print,
+
     Int(i32),
     True,
     False,
diff --git a/src/sexp/step.rs b/src/sexp/step.rs
index 816582c..11df257 100644
--- a/src/sexp/step.rs
+++ b/src/sexp/step.rs
@@ -521,6 +521,12 @@ impl SExp {
                 }
             },
 
+	    // Print
+	    SCons(op, l) if *op == Atom(Print) => {
+		println!("{}", *l);
+		Ok(Atom(Nil))
+	    },
+
             // t is value
             // ----------
             //   t -> t
diff --git a/src/type/check.rs b/src/type/check.rs
index e536ce7..77420e3 100644
--- a/src/type/check.rs
+++ b/src/type/check.rs
@@ -194,6 +194,7 @@ impl SExp {
                                 List(vec![VecType, vecof(vt("T"))])
                             )),
             Atom(Let)    => Ok(LetType),
+	    Atom(Print)  => Ok(arr(vt("_"), List(vec![]))),
 
 
             SCons(op, l) => {