diff --git a/core/src/lib.rs b/core/src/lib.rs
index 296e053..cb0edf8 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -7,7 +7,7 @@ mod svob;
 mod toktree;
 
 pub use svob::{SimpleVob, SimpleVobIter};
-pub use toktree::{Recognizer, SpecialToken, TokRxInfo, TokTrie, TokenId, TokenizerEnv, TokEnv};
+pub use toktree::{Recognizer, SpecialToken, TokEnv, TokRxInfo, TokTrie, TokenId, TokenizerEnv};
 
 /// Defines what is allowed in Branch
 #[derive(Serialize, Deserialize, Clone, Debug, Default)]
@@ -23,13 +23,12 @@ pub struct InferenceCapabilities {
     /// Backtracking is allowed.
     #[serde(default)]
     pub backtrack: bool,
-    
+
     /// More than one branch is allowed.
     #[serde(default)]
     pub fork: bool,
 }
 
-
 #[derive(Serialize, Deserialize, Debug, Clone)]
 pub struct StepArg {
     /// Sampling result for the previous iteration.
@@ -60,6 +59,14 @@ impl StepArg {
         acc_tokens.truncate(acc_tokens.len() - bt);
         acc_tokens.extend_from_slice(&self.tokens);
     }
+
+    pub fn from_splice(s: &Splice, sampled: Option<TokenId>) -> Self {
+        StepArg {
+            backtrack: s.backtrack,
+            tokens: s.ff_tokens.clone(),
+            sampled,
+        }
+    }
 }
 
 /*
@@ -137,13 +144,13 @@ impl<S> Branch<S> {
     }
 
     pub fn spliced(&self, sampled: TokenId) -> Splice {
-        self.find_splice(sampled).cloned().unwrap_or_else(|| {
-            Splice {
+        self.find_splice(sampled)
+            .cloned()
+            .unwrap_or_else(|| Splice {
                 when_sampled: vec![],
                 backtrack: 0,
                 ff_tokens: vec![sampled],
-            }
-        })
+            })
     }
 
     pub fn unconditional_splice(&self) -> Option<&Splice> {