From 702fa34c343aade8280c8e4d43e98c321d424160 Mon Sep 17 00:00:00 2001
From: Balazs Komuves <bkomuves@gmail.com>
Date: Thu, 29 Jan 2026 11:40:54 +0100
Subject: [PATCH] add functions to convert vectors of field elements between
 standard and Montgomery representation

---
 benches/iterated_perm.rs | 12 ++----------
 src/bn254/field.rs       | 23 ++++++++++++++++++-----
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/benches/iterated_perm.rs b/benches/iterated_perm.rs
index d826c6f..e46af17 100644
--- a/benches/iterated_perm.rs
+++ b/benches/iterated_perm.rs
@@ -26,17 +26,9 @@ fn initial_vector() -> [Felt; 3] {
 }
 
 pub fn poseidon1_permute_felt(input: [Felt; 3]) -> [Felt; 3] {
-  let mut state: [Mont; 3] = 
-    [ Felt::to_mont(input[0])
-    , Felt::to_mont(input[1])
-    , Felt::to_mont(input[2])
-    ];
+  let mut state: [Mont; 3] = Felt::to_mont_vec(input);
   state = poseidon::permutation::permute_mont_T3(state);
-  let out: [Felt; 3] = 
-    [ Felt::from_mont(state[0])
-    , Felt::from_mont(state[1])
-    , Felt::from_mont(state[2])
-    ];
+  let out: [Felt; 3] = Felt::from_mont_vec(state);
   out
 }
 
diff --git a/src/bn254/field.rs b/src/bn254/field.rs
index 52efb6d..72f9819 100644
--- a/src/bn254/field.rs
+++ b/src/bn254/field.rs
@@ -118,7 +118,12 @@ impl Felt {
     BigInt::is_lt_prime(felt.0)
   }
 
+  pub fn to_decimal_string(input: Felt) -> String {
+    BigInt::to_decimal_string(input.0)
+  }
+
   //------------------------------------
+  // conversion to/from bytes
 
   pub fn to_le_bytes(felt: Felt) -> [u8; 32] {
     BigInt::to_le_bytes(felt.0)
@@ -136,9 +141,12 @@ impl Felt {
     Felt(BigInt::from_be_bytes(buf))
   }
 
+  //------------------------------------
+  // conversion to/from Montgomery
+
   // convert to Montgomery representation
-  pub fn to_mont(fld: Felt) -> Mont {
-    Mont::unsafe_convert_from_big( fld.0 )
+  pub fn to_mont(felt: Felt) -> Mont {
+    Mont::unsafe_convert_from_big( felt.0 )
   }
 
   // convert from Montgomery representation
@@ -146,12 +154,17 @@ impl Felt {
     Felt(Mont::convert_to_big(mont))
   }
 
-  pub fn to_decimal_string(input: Felt) -> String {
-    BigInt::to_decimal_string(input.0)
+  pub fn to_mont_vec<const T: usize>(felts: [Felt; T]) -> [Mont; T] {
+    felts.map( |x| Felt::to_mont(x) )
+  }
+
+  pub fn from_mont_vec<const T: usize>(monts: [Mont;T] ) -> [Felt; T] {
+    monts.map( |x| Felt::from_mont(x) )
   }
 
   //------------------------------------
-
+  // basic operations
+  
   pub fn zero() -> Felt {
     Felt(BigInt::zero())
   }