diff --git a/src/buffer/factory.rs b/src/buffer/factory.rs
index f979196..05cf36d 100644
--- a/src/buffer/factory.rs
+++ b/src/buffer/factory.rs
@@ -2,10 +2,73 @@
 //! 
 //! a helper trait to produce Operation Sequences, knowing the current 
 //! state of the buffer
+//!
+//! ```rust
+//! use codemp::buffer::factory::{OperationFactory, SimpleOperationFactory};
+//!
+//! let mut factory = SimpleOperationFactory::from("");
+//! let op = factory.insert("asd", 0);
+//! factory.update(op)?;
+//! assert_eq!(factory.content(), "asd");
+//! # Ok::<(), codemp::ot::OTError>(())
+//! ```
+//!
+//! use [OperationFactory::insert] to add new characters at a specific index
+//!
+//! ```rust
+//! # use codemp::buffer::factory::{OperationFactory, SimpleOperationFactory};
+//! # let mut factory = SimpleOperationFactory::from("asd");
+//! factory.update(factory.insert(" dsa", 3))?;
+//! assert_eq!(factory.content(), "asd dsa");
+//! # Ok::<(), codemp::ot::OTError>(())
+//! ```
+//!
+//! use [OperationFactory::delta] to arbitrarily change text at any position
+//!
+//! ```rust
+//! # use codemp::buffer::factory::{OperationFactory, SimpleOperationFactory};
+//! # let mut factory = SimpleOperationFactory::from("asd dsa");
+//! let op = factory.delta(2, " xxx ", 5).expect("replaced region is equal to origin");
+//! factory.update(op)?;
+//! assert_eq!(factory.content(), "as xxx sa");
+//! # Ok::<(), codemp::ot::OTError>(())
+//! ```
+//!
+//! use [OperationFactory::delete] to remove characters from given index
+//!
+//! ```rust
+//! # use codemp::buffer::factory::{OperationFactory, SimpleOperationFactory};
+//! # let mut factory = SimpleOperationFactory::from("as xxx sa");
+//! factory.update(factory.delete(2, 5))?;
+//! assert_eq!(factory.content(), "assa");
+//! # Ok::<(), codemp::ot::OTError>(())
+//! ```
+//!
+//! use [OperationFactory::replace] to completely replace buffer content
+//!
+//! ```rust
+//! # use codemp::buffer::factory::{OperationFactory, SimpleOperationFactory};
+//! # let mut factory = SimpleOperationFactory::from("assa");
+//! let op = factory.replace("from scratch").expect("replace is equal to origin");
+//! factory.update(op)?;
+//! assert_eq!(factory.content(), "from scratch");
+//! # Ok::<(), codemp::ot::OTError>(())
+//! ```
+//!
+//! use [OperationFactory::cancel] to remove characters at index, but backwards
+//!
+//! ```rust
+//! # use codemp::buffer::factory::{OperationFactory, SimpleOperationFactory};
+//! # let mut factory = SimpleOperationFactory::from("from scratch");
+//! factory.update(factory.cancel(12, 8))?;
+//! assert_eq!(factory.content(), "from");
+//! # Ok::<(), codemp::ot::OTError>(())
+//! ```
+//!
 
 use std::ops::Range;
 
-use operational_transform::{OperationSeq, Operation};
+use operational_transform::{OperationSeq, Operation, OTError};
 use similar::{TextDiff, ChangeTag};
 
 /// calculate leading no-ops in given opseq
@@ -44,7 +107,7 @@ pub trait OperationFactory {
 		let mut out = OperationSeq::default();
 		let content = self.content();
 		let tail_skip = content.len() - end; // TODO len is number of bytes, not chars
-		let content_slice = &content[start..tail_skip];
+		let content_slice = &content[start..end];
 
 		if content_slice == txt {
 			// if slice equals given text, no operation should be taken
@@ -82,9 +145,9 @@ pub trait OperationFactory {
 	fn delete(&self, pos: u64, count: u64) -> OperationSeq {
 		let mut out = OperationSeq::default();
 		let len = self.content().len() as u64;
-		out.retain(pos - count);
+		out.retain(pos);
 		out.delete(count);
-		out.retain(len - pos);
+		out.retain(len - (pos+count));
 		out
 	}
 
@@ -92,9 +155,32 @@ pub trait OperationFactory {
 	fn cancel(&self, pos: u64, count: u64) -> OperationSeq {
 		let mut out = OperationSeq::default();
 		let len = self.content().len() as u64;
-		out.retain(pos);
+		out.retain(pos - count);
 		out.delete(count);
-		out.retain(len - (pos+count));
+		out.retain(len - pos);
 		out
 	}
 }
+
+/// a simple example operation factory that just wraps a string
+pub struct SimpleOperationFactory(String);
+
+impl SimpleOperationFactory {
+	/// applies given OperationSeq to underlying string, changing it
+	pub fn update(&mut self, op: OperationSeq) -> Result<(), OTError> {
+		self.0 = op.apply(&self.0)?;
+		Ok(())
+	}
+}
+
+impl From::<&str> for SimpleOperationFactory {
+	fn from(value: &str) -> Self {
+		SimpleOperationFactory(value.to_string())
+	}
+}
+
+impl OperationFactory for SimpleOperationFactory {
+	fn content(&self) -> String {
+		self.0.clone()
+	}
+}