diff --git a/Cargo.lock b/Cargo.lock
index 8f905a9..4123ffd 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -11,6 +11,6 @@ dependencies = [
 
 [[package]]
 name = "estring"
-version = "0.2.1"
+version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5d0069d8a2500e291e248b96dc353cf71e2693b278058fd2954b5ed90c836e77"
+checksum = "a7cc7b476dae2894e7fb8d37102acc505c8981f754d1cf44aaf666f20cf21e74"
diff --git a/Cargo.toml b/Cargo.toml
index cf5cbc0..63c4254 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,6 +20,7 @@ all-features = true
 default = []
 low-level = ["estring/low-level"]
 structs = ["estring/structs"]
+aggs = ["estring/aggs"]
 
 # deprecated
 number = []
@@ -27,12 +28,12 @@ bool  = []
 vec = ["structs"]
 
 [dependencies]
-estring = "0.2"
+estring = "0.3"
 
 [badges]
 maintenance = { status = "actively-developed" }
 
 [[example]]
 name = "calc"
-required-features = ["structs"]
+required-features = ["structs", "aggs"]
 
diff --git a/examples/README.md b/examples/README.md
index e8dfe34..0e5a7b4 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -11,5 +11,3 @@ E=2*2-1-1+5*3-10 cargo run --example calc --all-features
 Limits (yet):
 
 - Supports `*`, `+`, `-`
-- You cannot start from a negative number. `E=-10`. Solution: start from `0`.
-  `E=0-10`.
diff --git a/examples/calc.rs b/examples/calc.rs
index 94e3801..e4c23b4 100644
--- a/examples/calc.rs
+++ b/examples/calc.rs
@@ -1,16 +1,18 @@
-use enve::SepVec;
+use enve::{
+    estring::{self, Aggregatable, Aggregate},
+    Product, SepVec, Sum,
+};
 
-type MinusVec<T> = SepVec<T, '-'>;
 type PlusVec<T> = SepVec<T, '+'>;
 type MulVec<T> = SepVec<T, '*'>;
 
 const HELP_MESSAGE: &str = "
 USAGE:
-E=10+10*2+4 cargo run --example calc --all-features
+E=10+10*2-4 cargo run --example calc --all-features
 ";
 
 fn main() -> Result<(), enve::Error> {
-    let res: f32 = enve::get::<PlusVec<MinusVec<MulVec<f32>>>>("E")
+    let res: f32 = enve::get::<Sum<PlusVec<MinusVec<Product<MulVec<f32>>>>>>("E")
         .map_err(|err| {
             match err {
                 enve::Error::NotPresent => eprintln!("The expression was not found"),
@@ -21,16 +23,46 @@ fn main() -> Result<(), enve::Error> {
             std::process::exit(0);
         })
         .unwrap()
-        .iter()
-        .map(|p| {
-            p.iter()
-                .map(|m| m.iter().product::<f32>())
-                .reduce(|acc, v| acc - v)
-                .unwrap_or_default()
-        })
-        .sum::<f32>();
+        .agg();
 
     println!("result: {}", res);
 
     Ok(())
 }
+
+struct MinusVec<T>(Vec<T>);
+
+impl<T> estring::ParseFragment for MinusVec<T>
+where
+    T: estring::ParseFragment,
+{
+    fn parse_frag(es: estring::EString) -> estring::Result<Self> {
+        let mut prev: Option<&str> = None;
+        es.split('-')
+            .map(str::trim)
+            .map(|val| match prev.replace(val) {
+                None => String::from(val),
+                Some(_) => {
+                    let mut s = val.to_owned();
+                    s.insert(0, '-');
+                    s
+                }
+            })
+            .filter(|val| !val.is_empty())
+            .map(estring::EString::from)
+            .map(T::parse_frag)
+            .collect::<estring::Result<Vec<T>>>()
+            .map(Self)
+    }
+}
+
+impl<T> estring::Aggregatable for MinusVec<T>
+where
+    T: Aggregatable,
+{
+    type Item = T::Item;
+
+    fn items(self) -> Vec<Self::Item> {
+        self.0.into_iter().flat_map(T::items).collect()
+    }
+}
diff --git a/src/estr.rs b/src/estr.rs
index 95ffb1d..d3ca26f 100644
--- a/src/estr.rs
+++ b/src/estr.rs
@@ -4,6 +4,9 @@ mod structs;
 pub use structs::{CommaVec, SemiVec};
 
 pub use estring::core::EString;
+
+#[cfg(feature = "aggs")]
+pub use estring::agg::*;
 #[cfg(feature = "low-level")]
 pub use estring::low::*;
 #[cfg(feature = "structs")]