From fc310a2a398566c2f6128560dcf8915d5a3a1414 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Mon, 12 Feb 2024 12:10:28 +0100
Subject: [PATCH] circuit: fix comments

endianness only applies to byte order, not to bit order
---
 circuit/binary_compare.circom | 3 ++-
 circuit/extract_bits.circom   | 4 ++--
 circuit/merkle.circom         | 6 +++---
 circuit/misc.circom           | 2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/circuit/binary_compare.circom b/circuit/binary_compare.circom
index 3796d8c..5d1c7e1 100644
--- a/circuit/binary_compare.circom
+++ b/circuit/binary_compare.circom
@@ -3,7 +3,8 @@ pragma circom 2.0.0;
 //------------------------------------------------------------------------------
 
 //
-// given two numbers in `n`-bit binary decomposition (little-endian), we compute
+// given two numbers in `n`-bit binary decomposition
+// (least significant bit first), we compute
 //
 //             /  -1   if   A <  B
 //   out  :=  {    0   if   A == B
diff --git a/circuit/extract_bits.circom b/circuit/extract_bits.circom
index 41d14bf..248ff35 100644
--- a/circuit/extract_bits.circom
+++ b/circuit/extract_bits.circom
@@ -23,7 +23,7 @@ template ExtractLowerBits(n) {
   component tb = ToBits(254);      // note: 2^253 < r < 2^254
   tb.inp <== inp;
 
-  // bits of field prime `r` in little-endian order
+  // bits of field prime `r`, least significant bit first
   var primeBits[254] = [1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,0,0,1,0,0,1,1,0,1,0,1,1,1,1,1,0,0,0,0,1,1,1,1,1,0,0,0,0,1,0,1,0,0,0,1,0,0,1,0,0,0,0,1,1,1,0,1,0,0,1,1,1,0,1,1,0,0,1,1,1,1,0,0,0,0,1,0,0,1,0,0,0,0,1,0,1,1,1,1,1,0,0,1,1,0,0,0,0,0,1,0,1,0,0,1,0,1,1,1,0,1,0,0,0,0,1,1,0,1,0,1,0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,0,1,1,0,1,1,0,1,1,0,1,0,0,0,1,0,0,0,0,0,1,0,1,0,0,0,0,1,1,1,0,1,1,0,0,1,0,1,0,0,0,0,0,0,0,1,0,1,1,0,0,0,1,1,0,0,1,0,0,0,0,1,1,1,0,1,0,0,1,1,1,0,0,1,1,1,0,0,1,0,0,0,1,0,0,1,1,0,0,0,0,0,1,1];
 
   // enforce that the binary representation is < r
@@ -56,7 +56,7 @@ template ExtractLowerBits_testfield65537(n) {
   component tb = ToBits(18);      // note: 2^16 < r < 2^18
   tb.inp <== inp;
 
-  // bits of field prime `r` in little-endian order
+  // bits of field prime `r`, least significant bit first
   var primeBits[18] = [1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0];
 
   // enforce that the binary representation is < r
diff --git a/circuit/merkle.circom b/circuit/merkle.circom
index a13e316..b1f564c 100644
--- a/circuit/merkle.circom
+++ b/circuit/merkle.circom
@@ -14,7 +14,7 @@ include "misc.circom";
 //
 // inputs and outputs:
 //  - leaf:        the leaf hash
-//  - pathBits:    the linear index of the leaf, in binary decomposition (little-endian)
+//  - pathBits:    the linear index of the leaf, in binary decomposition (least significant bit first)
 //  - lastBits:    the index of the last leaf (= nLeaves-1), in binary decomposition
 //  - maskBits:    the bits of the the mask `2^ceilingLog2(size) - 1`
 //  - merklePath:  the Merkle inclusion proof (required hashes, starting from the leaf and ending near the root)
@@ -37,8 +37,8 @@ template RootFromMerklePath( maxDepth ) {
   signal aux[ maxDepth+1 ];
   aux[0] <== leaf;
 
-  // compute which prefixes (in big-endian) of the index is
-  // the same as the corresponding prefix of the last index
+  // compute which binary postfixes of the index is the same as the
+  // corresponding postfix of the last index
   component eq[ maxDepth ];
   signal isLast[ maxDepth+1 ];
   isLast[ maxDepth ] <== 1;
diff --git a/circuit/misc.circom b/circuit/misc.circom
index 3feb175..c9065bc 100644
--- a/circuit/misc.circom
+++ b/circuit/misc.circom
@@ -1,7 +1,7 @@
 pragma circom 2.0.0;
 
 //------------------------------------------------------------------------------
-// decompose an n-bit number into bits
+// decompose an n-bit number into bits (least significant bit first)
 
 template ToBits(n) {
   signal input  inp;