diff --git a/src/compiler.cairo b/src/compiler.cairo
index 7d108f6b..2ce91900 100644
--- a/src/compiler.cairo
+++ b/src/compiler.cairo
@@ -332,7 +332,7 @@ pub impl CompilerImpl of CompilerTrait {
         let mut current = "";
         let mut i = 0;
         let script_len = script.len();
-        while i < script_len {
+        while i != script_len {
             let char = script[i].into();
             if char == seperator {
                 if current == "" {
@@ -354,7 +354,7 @@ pub impl CompilerImpl of CompilerTrait {
         // Compile the script into bytecode
         let mut i = 0;
         let script_len = split_script.len();
-        while i < script_len {
+        while i != script_len {
             let script_item = split_script.at(i);
             if utils::is_hex(script_item) {
                 ByteArrayTrait::append(ref bytecode, @utils::hex_to_bytecode(script_item));
diff --git a/src/engine.cairo b/src/engine.cairo
index 7469793e..d43c4008 100644
--- a/src/engine.cairo
+++ b/src/engine.cairo
@@ -141,7 +141,7 @@ pub impl EngineImpl of EngineTrait {
 
         let mut i = 0;
         let mut valid_sizes = true;
-        while i < engine.scripts.len() {
+        while i != engine.scripts.len() {
             let script = *(engine.scripts[i]);
             if script.len() > MAX_SCRIPT_SIZE {
                 valid_sizes = false;
@@ -181,7 +181,7 @@ pub impl EngineImpl of EngineTrait {
                     let mut remaining = "";
                     let mut i = 1;
                     // TODO: Optimize
-                    while i < sig_clone.len() {
+                    while i != sig_clone.len() {
                         remaining.append_byte(sig_clone[i]);
                         i += 1;
                     };
@@ -225,7 +225,8 @@ pub impl EngineImpl of EngineTrait {
         let script: @ByteArray = *(self.scripts[0]);
         let mut i = 0;
         let mut is_push_only = true;
-        while i < script.len() {
+        while i != script.len() {
+            // TODO: Error handling if i outside bounds
             let opcode = script[i];
             if opcode > Opcode::OP_16 {
                 is_push_only = false;
@@ -255,7 +256,7 @@ pub impl EngineImpl of EngineTrait {
         if end > script.len() {
             return Result::Err(Error::SCRIPT_INVALID);
         }
-        while i < end {
+        while i != end {
             data.append_byte(script[i]);
             i += 1;
         };
@@ -271,7 +272,7 @@ pub impl EngineImpl of EngineTrait {
         if end > script.len() {
             return Result::Err(Error::SCRIPT_INVALID);
         }
-        while i < end {
+        while i != end {
             data.append_byte(script[i]);
             i += 1;
         };
@@ -408,6 +409,7 @@ pub impl EngineImpl of EngineTrait {
 
     fn execute(ref self: Engine) -> Result<ByteArray, felt252> {
         let mut err = '';
+        // TODO: Optimize with != instead of < and check for bounds errors within the loop
         while self.script_idx < self.scripts.len() {
             let script: @ByteArray = *self.scripts[self.script_idx];
             while self.opcode_idx < script.len() {
@@ -532,7 +534,7 @@ pub impl EngineImpl of EngineTrait {
             let ret_val = top_stack.clone();
             let mut is_ok = false;
             let mut i = 0;
-            while i < top_stack.len() {
+            while i != top_stack.len() {
                 if top_stack[i] != 0 {
                     is_ok = true;
                     break;
@@ -624,7 +626,7 @@ pub impl EngineImpl of EngineTrait {
 
         let mut sub_script = "";
         let mut i = self.last_code_sep;
-        while i < script.len() {
+        while i != script.len() {
             sub_script.append_byte(script[i]);
             i += 1;
         };
diff --git a/src/errors.cairo b/src/errors.cairo
index 99f75704..447347c6 100644
--- a/src/errors.cairo
+++ b/src/errors.cairo
@@ -32,7 +32,7 @@ pub fn byte_array_err(err: felt252) -> ByteArray {
     let mut bytes = "";
     let mut word_len = 0;
     let mut byte_shift: u256 = 256;
-    while (err.into() / byte_shift) > 0 {
+    while (err.into() / byte_shift) != 0 {
         word_len += 1;
         byte_shift *= 256;
     };
diff --git a/src/opcodes/crypto.cairo b/src/opcodes/crypto.cairo
index 62f0f174..62c96284 100644
--- a/src/opcodes/crypto.cairo
+++ b/src/opcodes/crypto.cairo
@@ -17,7 +17,7 @@ pub fn opcode_sha256(ref engine: Engine) -> Result<(), felt252> {
     let res = compute_sha256_byte_array(arr).span();
     let mut res_bytes: ByteArray = "";
     let mut i: usize = 0;
-    while i < res.len() {
+    while i != res.len() {
         res_bytes.append_word((*res[i]).into(), 4);
         i += 1;
     };
@@ -30,7 +30,7 @@ pub fn opcode_hash160(ref engine: Engine) -> Result<(), felt252> {
     let res = compute_sha256_byte_array(@m).span();
     let mut res_bytes: ByteArray = "";
     let mut i: usize = 0;
-    while i < res.len() {
+    while i != res.len() {
         res_bytes.append_word((*res[i]).into(), 4);
         i += 1;
     };
@@ -44,14 +44,14 @@ pub fn opcode_hash256(ref engine: Engine) -> Result<(), felt252> {
     let res = compute_sha256_byte_array(@m).span();
     let mut res_bytes: ByteArray = "";
     let mut i: usize = 0;
-    while i < res.len() {
+    while i != res.len() {
         res_bytes.append_word((*res[i]).into(), 4);
         i += 1;
     };
     let res2 = compute_sha256_byte_array(@res_bytes).span();
     let mut res2_bytes: ByteArray = "";
     let mut j: usize = 0;
-    while j < res2.len() {
+    while j != res2.len() {
         res2_bytes.append_word((*res2[j]).into(), 4);
         j += 1;
     };
@@ -128,7 +128,7 @@ pub fn opcode_checkmultisig(ref engine: Engine) -> Result<(), felt252> {
     let mut pub_keys = ArrayTrait::<ByteArray>::new();
     let mut i: i64 = 0;
     let mut err: felt252 = 0;
-    while i < num_pub_keys {
+    while i != num_pub_keys {
         match engine.dstack.pop_byte_array() {
             Result::Ok(pk) => pub_keys.append(pk),
             Result::Err(e) => err = e
@@ -151,7 +151,7 @@ pub fn opcode_checkmultisig(ref engine: Engine) -> Result<(), felt252> {
     let mut sigs = ArrayTrait::<ByteArray>::new();
     i = 0;
     err = 0;
-    while i < num_sigs {
+    while i != num_sigs {
         match engine.dstack.pop_byte_array() {
             Result::Ok(s) => sigs.append(s),
             Result::Err(e) => err = e
@@ -173,7 +173,7 @@ pub fn opcode_checkmultisig(ref engine: Engine) -> Result<(), felt252> {
 
     // TODO: add witness context inside engine to check if witness is active
     let mut s: u32 = 0;
-    while s < sigs.len() {
+    while s != sigs.len() {
         script = signature::remove_signature(script, sigs.at(s));
         s += 1;
     };
@@ -183,7 +183,7 @@ pub fn opcode_checkmultisig(ref engine: Engine) -> Result<(), felt252> {
     let mut pub_key_idx: i64 = -1;
     let mut sig_idx: i64 = 0;
 
-    while num_sigs > 0 {
+    while num_sigs != 0 {
         pub_key_idx += 1;
         num_pub_keys -= 1;
         if num_sigs > num_pub_keys {
diff --git a/src/opcodes/opcodes.cairo b/src/opcodes/opcodes.cairo
index 1b14cbb5..34e2d015 100644
--- a/src/opcodes/opcodes.cairo
+++ b/src/opcodes/opcodes.cairo
@@ -456,7 +456,7 @@ pub mod Opcode {
         if end > script.len() {
             return Result::Err(Error::SCRIPT_INVALID);
         }
-        while i < end {
+        while i != end {
             data.append_byte(script[i]);
             i += 1;
         };
diff --git a/src/opcodes/tests/test_constants.cairo b/src/opcodes/tests/test_constants.cairo
index 5c03e226..ee01fe5a 100644
--- a/src/opcodes/tests/test_constants.cairo
+++ b/src/opcodes/tests/test_constants.cairo
@@ -61,7 +61,7 @@ fn test_op_1negate() {
 fn test_op_data(value: u8) {
     let mut hex_data: ByteArray = "0x";
     let mut i = 0;
-    while i < value {
+    while i != value {
         hex_data.append_word(int_to_hex(i + 1), 2);
         i += 1;
     };
@@ -78,7 +78,7 @@ fn test_op_data(value: u8) {
 fn test_op_data_all() {
     let mut n = 1;
 
-    while n <= 75 {
+    while n != 76 {
         test_op_data(n);
         n += 1;
     }
diff --git a/src/opcodes/tests/test_disabled.cairo b/src/opcodes/tests/test_disabled.cairo
index 5cf85bbb..c2d5ff0f 100644
--- a/src/opcodes/tests/test_disabled.cairo
+++ b/src/opcodes/tests/test_disabled.cairo
@@ -26,7 +26,7 @@ fn disabled_opcodes() -> core::array::Array<ByteArray> {
 fn test_op_code_disabled() {
     let disabled_opcodes = disabled_opcodes();
     let mut i: usize = 0;
-    while i < disabled_opcodes.len() {
+    while i != disabled_opcodes.len() {
         let mut engine = utils::test_compile_and_run_err(
             disabled_opcodes.at(i).clone(), Error::OPCODE_DISABLED
         );
@@ -39,7 +39,7 @@ fn test_op_code_disabled() {
 fn test_disabled_opcodes_if_block() {
     let disabled_opcodes = disabled_opcodes();
     let mut i: usize = 0;
-    while i < disabled_opcodes.len() {
+    while i != disabled_opcodes.len() {
         let program = format!(
             "OP_1 OP_IF {} OP_ELSE OP_DROP OP_ENDIF", disabled_opcodes.at(i).clone()
         );
@@ -53,7 +53,7 @@ fn test_disabled_opcodes_if_block() {
 fn test_disabled_opcodes_else_block() {
     let disabled_opcodes = disabled_opcodes();
     let mut i: usize = 0;
-    while i < disabled_opcodes.len() {
+    while i != disabled_opcodes.len() {
         let program = format!(
             "OP_0 OP_IF OP_DROP OP_ELSE {} OP_ENDIF", disabled_opcodes.at(i).clone()
         );
@@ -68,7 +68,7 @@ fn test_disabled_opcodes_else_block() {
 fn test_disabled_opcode_in_unexecd_if_block() {
     let disabled_opcodes = disabled_opcodes();
     let mut i: usize = 0;
-    while i < disabled_opcodes.len() {
+    while i != disabled_opcodes.len() {
         let program = format!(
             "OP_0 OP_IF {} OP_ELSE OP_DROP OP_ENDIF", disabled_opcodes.at(i).clone()
         );
diff --git a/src/opcodes/tests/test_stack.cairo b/src/opcodes/tests/test_stack.cairo
index 4d13a767..52740319 100644
--- a/src/opcodes/tests/test_stack.cairo
+++ b/src/opcodes/tests/test_stack.cairo
@@ -296,7 +296,7 @@ fn test_max_stack() {
     let mut program: ByteArray = "";
     let op_1_string = "OP_1 ";
     let mut index: u64 = 0;
-    while index < 1000 {
+    while index != 1000 {
         program.append(@op_1_string);
         index += 1;
     };
@@ -310,7 +310,7 @@ fn test_exceed_stack() {
     let mut program: ByteArray = "";
     let op_1_string = "OP_1 ";
     let mut index: u64 = 0;
-    while index < 1001 {
+    while index != 1001 {
         program.append(@op_1_string);
         index += 1;
     };
diff --git a/src/scriptflags.cairo b/src/scriptflags.cairo
index 02e76797..51be0575 100644
--- a/src/scriptflags.cairo
+++ b/src/scriptflags.cairo
@@ -121,7 +121,7 @@ pub fn parse_flags(flags: ByteArray) -> u32 {
     let mut current = "";
     let mut i = 0;
     let flags_len = flags.len();
-    while i < flags_len {
+    while i != flags_len {
         let char = flags[i].into();
         if char == seperator {
             if current == "" {
@@ -143,7 +143,7 @@ pub fn parse_flags(flags: ByteArray) -> u32 {
     // Compile the flags into a single integer.
     let mut i = 0;
     let flags_len = split_flags.len();
-    while i < flags_len {
+    while i != flags_len {
         let flag = split_flags.at(i);
         let flag_value = flag_from_string(utils::byte_array_to_felt252_be(flag));
         script_flags += flag_value;
diff --git a/src/scriptnum/scriptnum.cairo b/src/scriptnum/scriptnum.cairo
index 44030aab..89407eb7 100644
--- a/src/scriptnum/scriptnum.cairo
+++ b/src/scriptnum/scriptnum.cairo
@@ -77,7 +77,7 @@ pub mod ScriptNum {
             return Result::Ok(0);
         }
         let snap_input = @input;
-        while i < snap_input.len() - 1 {
+        while i != snap_input.len() - 1 {
             result += snap_input.at(i).unwrap().into() * multiplier;
             multiplier *= BYTESHIFT;
             i += 1;
@@ -117,7 +117,7 @@ pub mod ScriptNum {
             return Result::Ok(0);
         }
         let snap_input = @input;
-        while i < snap_input.len() - 1 {
+        while i != snap_input.len() - 1 {
             result += snap_input.at(i).unwrap().into() * multiplier;
             multiplier *= BYTESHIFT;
             i += 1;
diff --git a/src/signature/sighash.cairo b/src/signature/sighash.cairo
index efd55b60..c2d87109 100644
--- a/src/signature/sighash.cairo
+++ b/src/signature/sighash.cairo
@@ -48,7 +48,7 @@ pub fn calc_witness_transaction_hash(
     // Serialize each input in the transaction.
     let input_len: usize = transaction.transaction_inputs.len();
     let mut i: usize = 0;
-    while i < input_len {
+    while i != input_len {
         let input: @TransactionInput = transaction.transaction_inputs.at(i);
 
         let input_txid: u256 = *input.previous_outpoint.txid;
@@ -69,7 +69,7 @@ pub fn calc_witness_transaction_hash(
         let output_len: usize = transaction.transaction_outputs.len();
 
         i = 0;
-        while i < output_len {
+        while i != output_len {
             let output: @TransactionOutput = transaction.transaction_outputs.at(i);
             let value: i64 = *output.value;
             let script: @ByteArray = output.publickey_script;
@@ -133,7 +133,7 @@ pub fn calc_witness_transaction_hash(
         sig_hash_bytes.append_byte(0xa9);
         sig_hash_bytes.append_byte(0x14);
         i = 2;
-        while i < sub_script.len() {
+        while i != sub_script.len() {
             sig_hash_bytes.append_byte(sub_script[i]);
             i += 1;
         };
diff --git a/src/signature/signature.cairo b/src/signature/signature.cairo
index ea5124aa..1618076e 100644
--- a/src/signature/signature.cairo
+++ b/src/signature/signature.cairo
@@ -62,7 +62,7 @@ pub fn compare_data(script: @ByteArray, sig_bytes: @ByteArray, i: u32, push_data
     let mut len: usize = push_data.into();
     let mut found = true;
 
-    while j < len {
+    while j != len {
         if script[i + j + 1] != sig_bytes[j] {
             found = false;
             break;
@@ -296,7 +296,7 @@ pub fn parse_signature(sig_bytes: @ByteArray) -> Result<Signature, felt252> {
     let mut i = 0;
 
     //Strip leading zero
-    while s_len > 0 && sig_bytes[i + r_len + 6] == 0x00 {
+    while s_len != 0 && sig_bytes[i + r_len + 6] == 0x00 {
         sig_len -= 1;
         s_len -= 1;
         s_offset += 1;
@@ -307,7 +307,7 @@ pub fn parse_signature(sig_bytes: @ByteArray) -> Result<Signature, felt252> {
 
     i = 0;
 
-    while r_len > 0 && sig_bytes[i + 4] == 0x00 {
+    while r_len != 0 && sig_bytes[i + 4] == 0x00 {
         sig_len -= 1;
         r_len -= 1;
         r_offset += 1;
diff --git a/src/signature/utils.cairo b/src/signature/utils.cairo
index 76f34171..f3292c3d 100644
--- a/src/signature/utils.cairo
+++ b/src/signature/utils.cairo
@@ -51,7 +51,7 @@ pub fn transaction_procedure(
         TransactionOutput
     >::new();
 
-    while i < transaction_input.len() {
+    while i != transaction_input.len() {
         // TODO: Optimize this
         let mut temp_transaction_input: TransactionInput = transaction_input[i].clone();
 
diff --git a/src/stack.cairo b/src/stack.cairo
index 5784f841..e4d96441 100644
--- a/src/stack.cairo
+++ b/src/stack.cairo
@@ -97,7 +97,7 @@ pub impl ScriptStackImpl of ScriptStackTrait {
 
     fn print(ref self: ScriptStack) {
         let mut i = self.len;
-        while i > 0 {
+        while i != 0 {
             i -= 1;
             self.print_element(i.into());
         }
@@ -106,7 +106,7 @@ pub impl ScriptStackImpl of ScriptStackTrait {
     fn json(ref self: ScriptStack) {
         let mut i = 0;
         print!("[");
-        while i < self.len {
+        while i != self.len {
             let (entry, arr) = self.data.entry(i.into());
             let arr = arr.deref();
             print!("\"{}\"", utils::bytecode_to_hex(@arr.clone()));
@@ -126,7 +126,7 @@ pub impl ScriptStackImpl of ScriptStackTrait {
         let mut err = '';
         let entry_index = 3 * n - 1;
         let mut i = n;
-        while i > 0 {
+        while i != 0 {
             let res = self.nip_n(entry_index);
             if res.is_err() {
                 err = res.unwrap_err();
@@ -144,7 +144,7 @@ pub impl ScriptStackImpl of ScriptStackTrait {
     fn stack_to_span(ref self: ScriptStack) -> Span<ByteArray> {
         let mut result = array![];
         let mut i = 0;
-        while i < self.len {
+        while i != self.len {
             let (entry, arr) = self.data.entry(i.into());
             let arr = arr.deref();
             result.append(arr.clone());
@@ -161,7 +161,7 @@ pub impl ScriptStackImpl of ScriptStackTrait {
         }
         let mut i = n;
         let mut err = '';
-        while i > 0 {
+        while i != 0 {
             i -= 1;
             let value = self.peek_byte_array(n - 1);
             if value.is_err() {
@@ -191,7 +191,7 @@ pub impl ScriptStackImpl of ScriptStackTrait {
 
         // Shift all elements above idx down by one
         let mut i = 0;
-        while i < idx {
+        while i != idx {
             let next_value = self.peek_byte_array(idx - i - 1).unwrap();
             let (entry, _) = self.data.entry((self.len - idx + i - 1).into());
             self.data = entry.finalize(NullableTrait::new(next_value));
@@ -239,7 +239,7 @@ pub impl ScriptStackImpl of ScriptStackTrait {
         }
         let entry: u32 = (2 * n) - 1;
         let mut err = '';
-        while n > 0 {
+        while n != 0 {
             let res = self.peek_byte_array(entry);
             if res.is_err() {
                 err = res.unwrap_err();
@@ -263,7 +263,7 @@ pub impl ScriptStackImpl of ScriptStackTrait {
         self.len = 0;
         let mut i = start;
         let end = start + len;
-        while i < end {
+        while i != end {
             self.push_byte_array(stack.at(i).clone());
             i += 1;
         };
diff --git a/src/transaction.cairo b/src/transaction.cairo
index 948d8ff9..48d46519 100644
--- a/src/transaction.cairo
+++ b/src/transaction.cairo
@@ -117,7 +117,7 @@ pub impl TransactionImpl of TransactionTrait {
         // TODO: Byte orderings
         let mut i = 0;
         let mut inputs: Array<TransactionInput> = array![];
-        while i < input_len {
+        while i != input_len {
             let tx_id = u256 {
                 high: utils::byte_array_value_at_be(@raw, ref offset, 16).try_into().unwrap(),
                 low: utils::byte_array_value_at_be(@raw, ref offset, 16).try_into().unwrap(),
@@ -141,7 +141,7 @@ pub impl TransactionImpl of TransactionTrait {
         let output_len: u8 = utils::byte_array_value_at_le(@raw, ref offset, 1).try_into().unwrap();
         let mut i = 0;
         let mut outputs: Array<TransactionOutput> = array![];
-        while i < output_len {
+        while i != output_len {
             // TODO: negative values
             let value: i64 = utils::byte_array_value_at_le(@raw, ref offset, 8).try_into().unwrap();
             let script_len = utils::byte_array_value_at_le(@raw, ref offset, 1).try_into().unwrap();
@@ -178,7 +178,7 @@ pub impl TransactionImpl of TransactionTrait {
         let input_len: usize = self.transaction_inputs.len();
         bytes.append_word_rev(input_len.into(), utils::int_size_in_bytes(input_len));
         let mut i: usize = 0;
-        while i < input_len {
+        while i != input_len {
             let input: @TransactionInput = self.transaction_inputs.at(i);
             let input_txid: u256 = *input.previous_outpoint.txid;
             let vout: u32 = *input.previous_outpoint.vout;
@@ -200,7 +200,7 @@ pub impl TransactionImpl of TransactionTrait {
         let output_len: usize = self.transaction_outputs.len();
         bytes.append_word_rev(output_len.into(), utils::int_size_in_bytes(output_len));
         i = 0;
-        while i < output_len {
+        while i != output_len {
             let output: @TransactionOutput = self.transaction_outputs.at(i);
             let value: i64 = *output.value;
             let script: @ByteArray = output.publickey_script;
@@ -260,7 +260,7 @@ pub impl TransactionImpl of TransactionTrait {
         let mut total_out: i64 = 0;
         let output_len = self.transaction_outputs.len();
         let mut i = 0;
-        while i < output_len {
+        while i != output_len {
             let output = self.transaction_outputs.at(i);
             total_out += *output.value;
             i += 1;
diff --git a/src/utils.cairo b/src/utils.cairo
index e1987883..dff7a46d 100644
--- a/src/utils.cairo
+++ b/src/utils.cairo
@@ -57,7 +57,7 @@ pub fn hex_to_bytecode(script_item: @ByteArray) -> ByteArray {
     let mut i = 2;
     let mut bytecode = "";
     let script_item_len = script_item.len();
-    while i < script_item_len {
+    while i != script_item_len {
         let mut upper_half_byte = 0;
         let mut lower_half_byte = 0;
         if script_item[i] >= a_string_lower {
@@ -91,7 +91,7 @@ pub fn bytecode_to_hex(bytecode: @ByteArray) -> ByteArray {
     if bytecode_len == 0 {
         return "0x00";
     }
-    while i < bytecode_len {
+    while i != bytecode_len {
         let upper_half_byte = bytecode[i] / half_byte_shift;
         let lower_half_byte = bytecode[i] % half_byte_shift;
         let upper_half: u8 = if upper_half_byte < 10 {
@@ -142,7 +142,7 @@ pub fn string_to_bytecode(script_item: @ByteArray) -> ByteArray {
         bytecode.append_byte(Opcode::OP_PUSHDATA4);
         bytecode.append(@ScriptNum::wrap(word_len.into()));
     }
-    while i < end {
+    while i != end {
         bytecode.append_byte(script_item[i]);
         i += 1;
     };
@@ -162,7 +162,7 @@ pub fn number_to_bytecode(script_item: @ByteArray) -> ByteArray {
         i += 1;
     }
     let mut value: i64 = 0;
-    while i < script_item_len {
+    while i != script_item_len {
         value = value * 10 + script_item[i].into() - zero;
         i += 1;
     };
@@ -197,7 +197,7 @@ pub fn byte_array_to_felt252_be(byte_array: @ByteArray) -> felt252 {
     let mut value = 0;
     let mut i = 0;
     let byte_array_len = byte_array.len();
-    while i < byte_array_len {
+    while i != byte_array_len {
         value = value * byte_shift + byte_array[i].into();
         i += 1;
     };
@@ -224,7 +224,7 @@ pub fn byte_array_value_at_be(byte_array: @ByteArray, ref offset: usize, len: us
     let byte_shift = 256;
     let mut value = 0;
     let mut i = offset;
-    while i < offset + len {
+    while i != offset + len {
         value = value * byte_shift + byte_array[i].into();
         i += 1;
     };
@@ -251,7 +251,7 @@ pub fn byte_array_value_at_le(byte_array: @ByteArray, ref offset: usize, len: us
 pub fn sub_byte_array(byte_array: @ByteArray, ref offset: usize, len: usize) -> ByteArray {
     let mut sub_byte_array = "";
     let mut i = offset;
-    while i < offset + len {
+    while i != offset + len {
         sub_byte_array.append_byte(byte_array[i]);
         i += 1;
     };
@@ -264,7 +264,7 @@ pub fn felt252_to_byte_array(value: felt252) -> ByteArray {
     let byte_shift = 256;
     let mut byte_array = "";
     let mut valueU256: u256 = value.into();
-    while valueU256 > 0 {
+    while valueU256 != 0 {
         byte_array.append_byte((valueU256 % byte_shift).try_into().unwrap());
         valueU256 /= byte_shift;
     };
@@ -305,7 +305,7 @@ pub fn int_to_hex(value: u8) -> felt252 {
 pub fn byte_array_to_bool(bytes: @ByteArray) -> bool {
     let mut i = 0;
     let mut ret_bool = false;
-    while i < bytes.len() {
+    while i != bytes.len() {
         if bytes.at(i).unwrap() != 0 {
             // Can be negative zero
             if i == bytes.len() - 1 && bytes.at(i).unwrap() == 0x80 {
@@ -342,11 +342,11 @@ pub fn u256_from_byte_array_with_offset(arr: @ByteArray, offset: usize, len: usi
     if read_bytes > 16 {
         high_bytes = read_bytes - 16;
     }
-    while i < high_bytes {
+    while i != high_bytes {
         high = high * 256 + arr[i + offset].into();
         i += 1;
     };
-    while i < read_bytes {
+    while i != read_bytes {
         low = low * 256 + arr[i + offset].into();
         i += 1;
     };
@@ -357,7 +357,7 @@ pub fn int_size_in_bytes(u_32: u32) -> u32 {
     let mut value: u32 = u_32;
     let mut size = 0;
 
-    while value > 0 {
+    while value != 0 {
         size += 1;
         value /= 256;
     };
diff --git a/src/validate.cairo b/src/validate.cairo
index 93b08560..f22344ee 100644
--- a/src/validate.cairo
+++ b/src/validate.cairo
@@ -16,7 +16,7 @@ pub fn validate_transaction(
 
     let mut i = 0;
     let mut err = '';
-    while i < input_count {
+    while i != input_count {
         let utxo = utxo_hints[i];
         // TODO: Error handling
         let mut engine = EngineImpl::new(utxo.pubkey_script, tx.clone(), i, flags, *utxo.amount)
diff --git a/src/witness.cairo b/src/witness.cairo
index 233c49d9..71a84212 100644
--- a/src/witness.cairo
+++ b/src/witness.cairo
@@ -35,7 +35,7 @@ pub fn parse_witness_input(input: ByteArray) -> Array<ByteArray> {
     let mut witness_data: Array<ByteArray> = array![];
     let mut i = 0;
     let mut temp_witness: ByteArray = "";
-    while i < input.len() {
+    while i != input.len() {
         if input[i] == ',' {
             let witness_bytes = utils::hex_to_bytecode(@temp_witness);
             witness_data.append(witness_bytes);