4 files changed, 60 insertions, 11 deletions

diff --git a/README.md b/README.md
index 95981d5..816e4b9 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,16 @@ going to use the llvm `C` API and build our own safe wrapper specialized for
 this tutorial. The wrapper offers a similar interface as the `C++` API and is
 implemented in [`src/llvm/`](src/llvm/)
 
+## Demo
+
+```bash
+# Run kaleidoscope program from file.
+cargo run ks/<file>
+
+# Run REPL loop, parsing from stdin.
+cargo run
+```
+
 ## Documentation
 
 Rustdoc for this crate is available at
diff --git a/ks/forloop.ks b/ks/forloop.ks
new file mode 100644
index 0000000..0efa5c3
--- /dev/null
+++ b/ks/forloop.ks
@@ -0,0 +1,7 @@
+extern putchard(char);
+def printstar(n)
+  for i = 1, i < n, 1.0 in
+    putchard(42);  # ascii 42 = '*'
+
+# print 100 '*' characters
+printstar(100);
diff --git a/ks/ifelse.ks b/ks/ifelse.ks
new file mode 100644
index 0000000..3aa4778
--- /dev/null
+++ b/ks/ifelse.ks
@@ -0,0 +1,7 @@
+def fib(x)
+  if x < 3 then
+    1
+  else
+    fib(x-1)+fib(x-2);
+
+fib(10);
diff --git a/src/main.rs b/src/main.rs
index b660416..868706d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -130,17 +130,10 @@ where
     module.dump();
 }
 
-fn main() {
-    println!("Parse stdin.");
-    println!("ENTER to parse current input.");
-    println!("C-d   to exit.");
-
-    // Create lexer over stdin.
-    let lexer = Lexer::new(std::io::stdin().bytes().filter_map(|v| {
-        let v = v.ok()?;
-        Some(v.into())
-    }));
-
+fn run_kaleidoscope<I>(lexer: Lexer<I>)
+where
+    I: Iterator<Item = char>,
+{
     // Create parser for kaleidoscope.
     let mut parser = Parser::new(lexer);
 
@@ -155,3 +148,35 @@ fn main() {
     // De-allocate managed static LLVM data.
     llvm::shutdown();
 }
+
+fn main() {
+    match std::env::args().nth(1) {
+        Some(file) => {
+            println!("Parse {}.", file);
+
+            // Create lexer over file.
+            let lexer = Lexer::new(
+                std::fs::File::open(&file)
+                    .expect(&format!("Failed to open file {}!", file))
+                    .bytes()
+                    .filter_map(|v| {
+                        let v = v.ok()?;
+                        Some(v.into())
+                    }),
+            );
+            run_kaleidoscope(lexer);
+        }
+        None => {
+            println!("Parse stdin.");
+            println!("ENTER to parse current input.");
+            println!("C-d   to exit.");
+
+            // Create lexer over stdin.
+            let lexer = Lexer::new(std::io::stdin().bytes().filter_map(|v| {
+                let v = v.ok()?;
+                Some(v.into())
+            }));
+            run_kaleidoscope(lexer);
+        }
+    }
+}