diff --git a/TODO.md b/TODO.md
new file mode 100644
index 0000000..c585e1b
--- /dev/null
+++ b/TODO.md
@@ -0,0 +1,6 @@
+ 1. parse cli parameters
+ 2. read from stdin
+ 3. split stdin into columns (column/awk commands)
+ 3. execute every field command on it's corresponding column
+    [ ] execute a command on first text column
+ 4. print resulting concatenated columns
diff --git a/src/input.rs b/src/lib.rs
similarity index 72%
rename from src/input.rs
rename to src/lib.rs
index 74bf1d2..48e0d55 100644
--- a/src/input.rs
+++ b/src/lib.rs
@@ -3,12 +3,18 @@
 
 use regex::Regex;
 use std::result;
+use std::ops::Index;
+use std::slice::SliceIndex;
 
 pub const DEFAULT_SEP_PATTERN: &str = r"[\t]+";
 
 
 type Column = Vec<String>;
-type Columns = Vec<Column>;
+// type Columns = Vec<Column>;
+
+#[derive(Clone, Debug)]
+pub struct Columns(Vec<Column>);
+
 type Result<T> = result::Result<T, String>;
 
 
@@ -56,7 +62,36 @@ pub fn split_columns(text: &str, sep: &str) -> Result<Columns>  {
 
     eprintln!("{:?}", columns);
 
-    Ok(columns)
+    Ok(Columns(columns))
+}
+
+impl Columns {
+
+    //NOTE: is there a way to auto implement what's implemented in the wrapped type self.0 ?
+    fn len(&self) -> usize {
+        self.0.len()
+    }
+}
+
+// build Columns from &str
+impl TryFrom<&str> for Columns {
+    type Error = String;
+
+    fn try_from(value: &str) -> Result<Self> {
+        split_columns(value, DEFAULT_SEP_PATTERN)
+    }
+}
+
+// impl Index to allow indexing in our wrapped Vector
+impl <I> Index<I> for Columns
+where
+    I: SliceIndex<[Column]>,
+{
+    type Output = I::Output;
+
+    fn index(&self, index: I) -> &Self::Output {
+        self.0.index(index)
+    }
 }
 
 #[test]
@@ -99,3 +134,9 @@ fn test_re_split() {
     eprintln!("{:?}", fields);
     assert!(false);
 }
+
+#[test]
+fn test_columns_from_str() {
+    let res: Columns = "first column\tsecond column\t\tthird column".try_into().unwrap();
+    assert_eq!(res.len(), 3);
+}
diff --git a/src/main.rs b/src/main.rs
index 2ce2c29..b26653f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,10 +5,9 @@
  * . execute arbitrary shell commands to manipulate input
  * . dynamically generate field parameters ?
  */
-mod input;
 
 use clap::Parser;
-use input::DEFAULT_SEP_PATTERN;
+use colmap::DEFAULT_SEP_PATTERN;
 
 #[derive(Parser)]
 /// colmap - map commands to columns of text input
@@ -36,13 +35,6 @@ struct Cli {
 fn main() {
     let cli = Cli::parse();
 
-    // 1. parse cli parameters
-    // 2. read from stdin
-    // 3. split stdin into columns (column/awk commands)
-    // 3. execute every field command on it's corresponding column
-    //    [ ] execute a command on first text column
-    // 4. print resulting concatenated columns
-
     // if let None = cli.f1.as_deref() {
     //     eprintln!("no field --fX to operate on");
     //     process::exit(1);