Add taproot compiler example usage

Cargo.toml

@@ -40,3 +40,7 @@ name = "psbt"
 
 [[example]]
 name = "xpub_descriptors"
+
+[[example]]
+name = "taproot"
+required-features = ["compiler"]

examples/taproot.rs

@@ -0,0 +1,44 @@
+extern crate bitcoin;
+extern crate miniscript;
+
+use std::str::FromStr;
+
+#[cfg(feature = "compiler")]
+use miniscript::policy::Concrete;
+use miniscript::Descriptor;
+
+fn main() {
+    let policies_str = [
+        "or(1@pk(A),1@pk(B))",
+        "or(1@and(pk(A),pk(B)),1@pk(C))",
+        "or(9@or(10@or(1@pk(A),100@pk(D)),1@pk(B)),1@pk(C))",
+        "or(1@or(1@or(1@pk(A),1@pk(D)),1@pk(B)),1@pk(C))",
+        "or(1@pk(A),1@or(1@and(pk(B),pk(C)),1@and(pk(D),older(10))))",
+        "thresh(1,or(1@pk(A),1@pk(B)),or(1@pk(C),1@or(1@and(pk(E),pk(F)),1@pk(D))))",
+        "thresh(1,pk(Z),and(pk(A),or(1@pk(B),1@pk(C))),pk(D),or(1@or(1@pk(G),1@pk(E)),1@and(pk(F),pk(X))))",
+        "thresh(1,and(pk(A),or(1@pk(B),1@pk(C))),or(10@pk(D),7@pk(E)),or(2@or(1@pk(F),1@and(pk(G),pk(H))),7@pk(I)))"
+    ];
+    let unspendable_key = "UNSPENDABLE_KEY".to_string();
+    let policies: Vec<Concrete<String>> = policies_str
+        .into_iter()
+        .map(|x| Concrete::from_str(x).unwrap())
+        .collect();
+    let private_comp: Vec<Descriptor<String>> = policies
+        .iter()
+        .map(|pol| {
+            pol.compile_tr_private(Some(unspendable_key.clone()))
+                .unwrap()
+        })
+        .collect();
+    let default_comp: Vec<Descriptor<String>> = policies
+        .iter()
+        .map(|pol| pol.compile_tr(Some(unspendable_key.clone())).unwrap())
+        .collect();
+
+    for idx in 0..policies.len() {
+        println!("Example {}", idx + 1);
+        println!("Policy: {}", policies_str[idx]);
+        println!("Private compilation: {}", private_comp[idx]);
+        println!("Default compilation: {}\n", default_comp[idx]);
+    }
+}