Merge branch 'lash/safe-decay' into 'master'

Add burn method + minor bug fixes

See merge request cicnet/erc20-demurrage-token!12

CAVEAT

@@ -0,0 +1,5 @@
+The contract is intended for slow rates of decay (e.g. 2% per month). Very high levels of decay (2% per minute) will lead to overflows, and will need a more flexible implementation to support it.
+
+The contract is written with frequent usage in mind. If used for tokens with low usage freqency (e.g. several days idle), it is recommended to run a continuous process triggering the changePeriod() contract call, to reduce the amount of exponential calculation the application of demurrage will trigger.
+
+When changing the period, the supply for the consecutive period will be taken at the time of code execution, and thus not necessarily at the time when the redistribution period threshold was crossed. 

ROADMAP

@@ -0,0 +1,8 @@
+- 0.1.3
+	* Snapshot supply for crossed redistribution thresholds before minting new tokens.
+- 0.1.4
+	* Implement natural logarithm 
+- 0.1.5
+	* Port changes from SingleNocap to SingleCap
+- 0.2.0
+	* Make decay resolutions configurable, to support high levels of decay.

VERSION

@@ -0,0 +1 @@
+0.2.0

python/CHANGELOG

@@ -1,3 +1,9 @@
+- 0.2.0
+	* Add token burn function
+	* Fix gas leak when calculating decay on period change
+	* Remove all but SingleNocap contract in make install
+	* Make approve explicitly set value
+	* Add increaseAllowance and decreaseAllowance methods
 - 0.1.1
 	* Settable demurrage steps for apply demurrage cli tool
 - 0.1.0

python/erc20_demurrage_token/demurrage.py

@@ -9,8 +9,7 @@ from chainlib.eth.constant import ZERO_ADDRESS
 # local imports
 from .token import DemurrageToken
 
-logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger(__name__)
-logg = logging.getLogger()
 
 
 class DemurrageCalculator:

python/erc20_demurrage_token/runnable/apply.py

@@ -16,17 +16,7 @@ import math
 
 # external imports
 import confini
-from funga.eth.signer import EIP155Signer
+import chainlib.eth.cli
-from funga.eth.keystore.dict import DictKeystore
-from chainlib.chain import ChainSpec
-from chainlib.eth.nonce import (
-        RPCNonceOracle,
-        OverrideNonceOracle,
-        )
-from chainlib.eth.gas import (
-        RPCGasOracle,
-        OverrideGasOracle,
-        )
 from chainlib.eth.block import (
         block_latest,
         block_by_number,
@@ -35,8 +25,20 @@ from chainlib.eth.block import (
 from chainlib.eth.connection import EthHTTPConnection
 from chainlib.eth.tx import receipt
 from chainlib.eth.constant import ZERO_ADDRESS
-import chainlib.eth.cli
 from hexathon import to_int as hex_to_int
+import chainlib.eth.cli
+from chainlib.eth.settings import process_settings
+from chainlib.settings import ChainSettings
+from chainlib.eth.cli.arg import (
+        Arg,
+        ArgFlag,
+        process_args,
+        )
+from chainlib.eth.cli.config import (
+        Config,
+        process_config,
+        )
+from chainlib.eth.cli.log import process_log
 
 # local imports
 import erc20_demurrage_token
@@ -45,32 +47,38 @@ from erc20_demurrage_token import (
         DemurrageTokenSettings,
         )
 
-logging.basicConfig(level=logging.WARNING)
 logg = logging.getLogger()
 
-script_dir = os.path.dirname(__file__)
-data_dir = os.path.join(script_dir, '..', 'data')
 
-config_dir = os.path.join(data_dir, 'config')
+def process_config_local(config, arg, args, flags):
+    config.add(args.steps, '_STEPS', False)
+    return config
 
-arg_flags = chainlib.eth.cli.argflag_std_write | chainlib.eth.cli.Flag.EXEC
+
-argparser = chainlib.eth.cli.ArgumentParser(arg_flags)
+arg_flags = ArgFlag()
+arg = Arg(arg_flags)
+flags = arg_flags.STD_WRITE | arg_flags.EXEC | arg_flags.WALLET
+
+argparser = chainlib.eth.cli.ArgumentParser()
+argparser = process_args(argparser, arg, flags)
 argparser.add_argument('--steps', type=int, default=0, help='Max demurrage steps to apply per round')
 args = argparser.parse_args()
-config = chainlib.eth.cli.Config.from_args(args, arg_flags, default_fee_limit=DemurrageToken.gas(), base_config_dir=config_dir)
+
-config.add(args.steps, '_STEPS', False)
+logg = process_log(args, logg)
+
+config = Config()
+config = process_config(config, arg, args, flags)
+config = process_config_local(config, arg, args, flags)
 logg.debug('config loaded:\n{}'.format(config))
 
-wallet = chainlib.eth.cli.Wallet()
+settings = ChainSettings()
-wallet.from_config(config)
+settings = process_settings(settings, config)
-
+logg.debug('settings loaded:\n{}'.format(settings))
-rpc = chainlib.eth.cli.Rpc(wallet=wallet)
-conn = rpc.connect_by_config(config)
-
-chain_spec = ChainSpec.from_chain_str(config.get('CHAIN_SPEC'))
 
 
 def main():
+    chain_spec = settings.get('CHAIN_SPEC')
+    conn = settings.get('CONN')
     o = block_latest()
     r = conn.do(o)
  
@@ -87,9 +95,9 @@ def main():
     block_start_timestamp = block_start.timestamp
     block_start_datetime = datetime.datetime.fromtimestamp(block_start_timestamp)
 
-    gas_oracle = rpc.get_gas_oracle()
+    gas_oracle = settings.get('FEE_ORACLE')
     c = DemurrageToken(chain_spec, gas_oracle=gas_oracle)
-    o = c.demurrage_timestamp(config.get('_EXEC_ADDRESS'))
+    o = c.demurrage_timestamp(settings.get('EXEC'))
     r = conn.do(o)
 
     demurrage_timestamp = None
@@ -120,17 +128,17 @@ def main():
 
     last_tx_hash = None
     for i in range(rounds):
-        signer = rpc.get_signer()
+        signer = settings.get('SIGNER')
-        signer_address = rpc.get_sender_address()
+        signer_address = settings.get('SENDER_ADDRESS')
 
-        nonce_oracle = rpc.get_nonce_oracle()
+        nonce_oracle = settings.get('NONCE_ORACLE')
 
         c = DemurrageToken(chain_spec, signer=signer, gas_oracle=gas_oracle, nonce_oracle=nonce_oracle)
         (tx_hash_hex, o) = c.apply_demurrage(config.get('_EXEC_ADDRESS'), signer_address, limit=config.get('_STEPS'))
-        if config.get('_RPC_SEND'):
+        if settings.get('RPC_SEND'):
             print(tx_hash_hex)
             conn.do(o)
-            if config.get('_WAIT_ALL') or (i == rounds - 1 and config.get('_WAIT')):
+            if config.true('_WAIT_ALL') or (i == rounds - 1 and config.true('_WAIT')):
                 r = conn.wait(tx_hash_hex)
                 if r['status'] == 0:
                     sys.stderr.write('EVM revert while deploying contract. Wish I had more to tell you')

python/erc20_demurrage_token/runnable/deploy.py

@@ -14,21 +14,22 @@ import logging
 
 # external imports
 import confini
-from funga.eth.signer import EIP155Signer
-from funga.eth.keystore.dict import DictKeystore
-from chainlib.chain import ChainSpec
-from chainlib.eth.nonce import (
-        RPCNonceOracle,
-        OverrideNonceOracle,
-        )
-from chainlib.eth.gas import (
-        RPCGasOracle,
-        OverrideGasOracle,
-        )
 from chainlib.eth.connection import EthHTTPConnection
 from chainlib.eth.tx import receipt
 from chainlib.eth.constant import ZERO_ADDRESS
 import chainlib.eth.cli
+from chainlib.eth.settings import process_settings
+from chainlib.settings import ChainSettings
+from chainlib.eth.cli.arg import (
+        Arg,
+        ArgFlag,
+        process_args,
+        )
+from chainlib.eth.cli.config import (
+        Config,
+        process_config,
+        )
+from chainlib.eth.cli.log import process_log
 
 # local imports
 import erc20_demurrage_token
@@ -37,84 +38,75 @@ from erc20_demurrage_token import (
         DemurrageTokenSettings,
         )
 
-logging.basicConfig(level=logging.WARNING)
 logg = logging.getLogger()
 
-script_dir = os.path.dirname(__file__)
-data_dir = os.path.join(script_dir, '..', 'data')
 
-config_dir = os.path.join(data_dir, 'config')
+def process_config_local(config, arg, args, flags):
+    config.add(args.token_name, 'TOKEN_NAME', False)
+    config.add(args.token_symbol, 'TOKEN_SYMBOL', False)
+    config.add(args.token_decimals, 'TOKEN_DECIMALS', False)
+    config.add(args.sink_address, 'TOKEN_SINK_ADDRESS', False)
+    config.add(args.redistribution_period, 'TOKEN_REDISTRIBUTION_PERIOD', False)
+    config.add(args.demurrage_level, 'TOKEN_DEMURRAGE_LEVEL', False)
+    config.add(0, 'TOKEN_SUPPLY_LIMIT', False)
+    return config
 
-arg_flags = chainlib.eth.cli.argflag_std_write
+
-argparser = chainlib.eth.cli.ArgumentParser(arg_flags)
+arg_flags = ArgFlag()
+arg = Arg(arg_flags)
+flags = arg_flags.STD_WRITE | arg_flags.EXEC | arg_flags.WALLET
+
+argparser = chainlib.eth.cli.ArgumentParser()
+argparser = process_args(argparser, arg, flags)
 argparser.add_argument('--name', dest='token_name', type=str, help='Token name')
 argparser.add_argument('--symbol', dest='token_symbol', required=True, type=str, help='Token symbol')
 argparser.add_argument('--decimals', dest='token_decimals', type=int, help='Token decimals')
 argparser.add_argument('--sink-address', dest='sink_address', type=str, help='demurrage level,ppm per minute') 
-argparser.add_argument('--supply-limit', dest='supply_limit', type=int, help='token supply limit (0 = no limit)')
+#argparser.add_argument('--supply-limit', dest='supply_limit', type=int, help='token supply limit (0 = no limit)')
-argparser.add_argument('--redistribution-period', type=int, help='redistribution period, minutes (0 = deactivate)') # default 10080 = week
+argparser.add_argument('--redistribution-period', dest='redistribution_period', type=int, help='redistribution period, minutes (0 = deactivate)') # default 10080 = week
-argparser.add_argument('--multi', action='store_true', help='automatic redistribution')
+#argparser.add_argument('--multi', action='store_true', help='automatic redistribution')
 argparser.add_argument('--demurrage-level', dest='demurrage_level', type=int, help='demurrage level, ppm per minute') 
 args = argparser.parse_args()
 
-arg_flags = chainlib.eth.cli.argflag_std_write
+logg = process_log(args, logg)
 
-extra_args = {
+config = Config()
-        'redistribution_period': 'TOKEN_REDISTRIBUTION_PERIOD',
+config = process_config(config, arg, args, flags)
-        'demurrage_level': 'TOKEN_DEMURRAGE_LEVEL',
+config = process_config_local(config, arg, args, flags)
-        'supply_limit': 'TOKEN_SUPPLY_LIMIT',
-        'token_name': 'TOKEN_NAME',
-        'token_symbol': 'TOKEN_SYMBOL',
-        'token_decimals': 'TOKEN_DECIMALS',
-        'sink_address': 'TOKEN_SINK_ADDRESS',
-        'multi': None,
-        }
-config = chainlib.eth.cli.Config.from_args(args, arg_flags, extra_args=extra_args, default_fee_limit=DemurrageToken.gas(), base_config_dir=config_dir)
-
-if not bool(config.get('TOKEN_NAME')):
-    logg.info('token name not set, using symbol {} as name'.format(config.get('TOKEN_SYMBOL')))
-    config.add(config.get('TOKEN_SYMBOL'), 'TOKEN_NAME', True)
-
-if config.get('TOKEN_SUPPLY_LIMIT') == None:
-    config.add(0, 'TOKEN_SUPPLY_LIMIT', True)
-
-if config.get('TOKEN_REDISTRIBUTION_PERIOD') == None:
-    config.add(10800, 'TOKEN_REDISTRIBUTION_PERIOD', True)
 logg.debug('config loaded:\n{}'.format(config))
 
-wallet = chainlib.eth.cli.Wallet()
+settings = ChainSettings()
-wallet.from_config(config)
+settings = process_settings(settings, config)
+logg.debug('settings loaded:\n{}'.format(settings))
 
-rpc = chainlib.eth.cli.Rpc(wallet=wallet)
-conn = rpc.connect_by_config(config)
-
-chain_spec = ChainSpec.from_chain_str(config.get('CHAIN_SPEC'))
 
 def main():
-    signer = rpc.get_signer()
+    chain_spec = settings.get('CHAIN_SPEC')
-    signer_address = rpc.get_sender_address()
+    conn = settings.get('CONN')
+    signer = settings.get('SIGNER')
+    signer_address = settings.get('SENDER_ADDRESS')
 
-    gas_oracle = rpc.get_gas_oracle()
+    gas_oracle = settings.get('FEE_ORACLE')
-    nonce_oracle = rpc.get_nonce_oracle()
+    nonce_oracle = settings.get('NONCE_ORACLE')
 
     c = DemurrageToken(chain_spec, signer=signer, gas_oracle=gas_oracle, nonce_oracle=nonce_oracle)
-    settings = DemurrageTokenSettings()
+    token_settings = DemurrageTokenSettings()
-    settings.name = config.get('TOKEN_NAME')
+    token_settings.name = config.get('TOKEN_NAME')
-    settings.symbol = config.get('TOKEN_SYMBOL')
+    token_settings.symbol = config.get('TOKEN_SYMBOL')
-    settings.decimals = int(config.get('TOKEN_DECIMALS'))
+    token_settings.decimals = int(config.get('TOKEN_DECIMALS'))
-    settings.demurrage_level = int(config.get('TOKEN_DEMURRAGE_LEVEL'))
+    token_settings.demurrage_level = int(config.get('TOKEN_DEMURRAGE_LEVEL'))
-    settings.period_minutes = int(config.get('TOKEN_REDISTRIBUTION_PERIOD'))
+    token_settings.period_minutes = int(config.get('TOKEN_REDISTRIBUTION_PERIOD'))
-    settings.sink_address = config.get('TOKEN_SINK_ADDRESS')
+    token_settings.sink_address = config.get('TOKEN_SINK_ADDRESS')
 
     (tx_hash_hex, o) = c.constructor(
             signer_address,
-            settings,
+            token_settings,
             redistribute=config.true('_MULTI'),
             cap=int(config.get('TOKEN_SUPPLY_LIMIT')),
             )
-    if config.get('_RPC_SEND'):
+    if settings.get('RPC_SEND'):
         conn.do(o)
-        if config.get('_WAIT'):
+        if config.true('_WAIT'):
             r = conn.wait(tx_hash_hex)
             if r['status'] == 0:
                 sys.stderr.write('EVM revert while deploying contract. Wish I had more to tell you')

python/erc20_demurrage_token/token.py

@@ -117,6 +117,34 @@ class DemurrageToken(ERC20):
         return DemurrageToken.__bytecode[name]
 
 
+    def increase_allowance(self, contract_address, sender_address, address, value, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('increaseAllowance')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.typ(ABIContractType.UINT256)
+        enc.address(address)
+        enc.uint256(value)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def decrease_allowance(self, contract_address, sender_address, address, value, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('decreaseAllowance')
+        enc.typ(ABIContractType.ADDRESS)
+        enc.typ(ABIContractType.UINT256)
+        enc.address(address)
+        enc.uint256(value)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
     def add_minter(self, contract_address, sender_address, address, tx_format=TxFormat.JSONRPC):
         enc = ABIContractEncoder()
         enc.method('addMinter')
@@ -155,6 +183,33 @@ class DemurrageToken(ERC20):
         return tx
 
 
+    def burn(self, contract_address, sender_address, value, tx_format=TxFormat.JSONRPC):
+        enc = ABIContractEncoder()
+        enc.method('burn')
+        enc.typ(ABIContractType.UINT256)
+        enc.uint256(value)
+        data = enc.get()
+        tx = self.template(sender_address, contract_address, use_nonce=True)
+        tx = self.set_code(tx, data)
+        tx = self.finalize(tx, tx_format)
+        return tx
+
+
+    def total_burned(self, contract_address, sender_address=ZERO_ADDRESS, id_generator=None):
+        j = JSONRPCRequest(id_generator)
+        o = j.template()
+        o['method'] = 'eth_call'
+        enc = ABIContractEncoder()
+        enc.method('totalBurned')
+        data = add_0x(enc.get())
+        tx = self.template(sender_address, contract_address)
+        tx = self.set_code(tx, data)
+        o['params'].append(self.normalize(tx))
+        o['params'].append('latest')
+        o = j.finalize(o)
+        return o
+
+
     def to_base_amount(self, contract_address, value, sender_address=ZERO_ADDRESS, id_generator=None):
         j = JSONRPCRequest(id_generator)
         o = j.template()
@@ -526,6 +581,7 @@ class DemurrageToken(ERC20):
     def parse_supply_cap(self, v):
         return abi_decode_single(ABIContractType.UINT256, v)
 
+
     @classmethod
     def parse_grow_by(self, v):
         return abi_decode_single(ABIContractType.UINT256, v)
@@ -549,3 +605,8 @@ class DemurrageToken(ERC20):
     @classmethod
     def parse_resolution_factor(self, v):
         return abi_decode_single(ABIContractType.UINT256, v)
+
+
+    @classmethod
+    def parse_total_burned(self, v):
+        return abi_decode_single(ABIContractType.UINT256, v)

python/erc20_demurrage_token/unittest/base.py

@@ -20,7 +20,7 @@ from erc20_demurrage_token import (
         DemurrageToken,
         )
 
-logg = logging.getLogger()
+logg = logging.getLogger(__name__)
 
 #BLOCKTIME = 5 # seconds
 TAX_LEVEL = int(10000 * 2) # 2%
@@ -95,13 +95,6 @@ class TestDemurrage(EthTesterCase):
 
     def setUp(self):
         super(TestDemurrage, self).setUp()
-#        token_deploy = TestTokenDeploy()
-#        self.settings = token_deploy.settings
-#        self.sink_address = token_deploy.sink_address
-#        self.start_block = token_deploy.start_block
-#        self.start_time = token_deploy.start_time
-#        self.default_supply = self.default_supply
-#        self.default_supply_cap = self.default_supply_cap
         period = PERIOD
         try:
             period = getattr(self, 'period')
@@ -133,6 +126,13 @@ class TestDemurrage(EthTesterCase):
         logg.debug('asserted within lower {} <= {} <= {}'.format(lower_target, v, target))
 
 
+    def assert_within_greater(self, v, target, tolerance_ppm):
+        higher_target = target + (target * (tolerance_ppm / 1000000))
+        self.assertLessEqual(v, higher_target)
+        self.assertGreaterEqual(v, target)
+        logg.debug('asserted within lower {} <= {} <= {}'.format(target, v, higher_target))
+
+
     def tearDown(self):
         pass
 

python/requirements.txt

@@ -1,3 +1,3 @@
-chainlib-eth>=0.1.0,<0.2.0
+chainlib-eth~=0.4.6
-eth-erc20~=0.3.0
+eth-erc20~=0.5.1
 funga-eth~=0.6.0

python/run_tests.sh

@@ -6,15 +6,18 @@ set -e
 export PYTHONPATH=.
 
 #modes=(MultiNocap MultiCap SingleCap SingleNocap)
-modes=(SingleCap SingleNocap) # other contracts need to be updted
+#modes=(SingleCap SingleNocap) # other contracts need to be updted
+modes=(SingleNocap) # other contracts need to be updted
 for m in ${modes[@]}; do
 	ERC20_DEMURRAGE_TOKEN_TEST_MODE=$m python tests/test_basic.py
 	ERC20_DEMURRAGE_TOKEN_TEST_MODE=$m python tests/test_growth.py
 	ERC20_DEMURRAGE_TOKEN_TEST_MODE=$m python tests/test_amounts.py
 	ERC20_DEMURRAGE_TOKEN_TEST_MODE=$m python tests/test_single.py
+	ERC20_DEMURRAGE_TOKEN_TEST_MODE=$m python tests/test_burn.py
 done
 
-modes=(SingleCap) # other contracts need to be updted
+#modes=(SingleCap) # other contracts need to be updted
+modes=()
 for m in ${modes[@]}; do
 	ERC20_DEMURRAGE_TOKEN_TEST_MODE=$m python tests/test_period.py
 done
@@ -25,7 +28,8 @@ for m in ${modes[@]}; do
 	ERC20_DEMURRAGE_TOKEN_TEST_MODE=$m python tests/test_redistribution_single.py
 done
 
-modes=(MultiCap SingleCap)
+#modes=(MultiCap SingleCap)
+modes=()
 for m in ${modes[@]}; do
 	ERC20_DEMURRAGE_TOKEN_TEST_MODE=$m python tests/test_cap.py
 done

python/setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = erc20-demurrage-token
-version = 0.1.1
+version = 0.2.0
 description = ERC20 token with redistributed continual demurrage
 author = Louis Holbrook
 author_email = dev@holbrook.no

python/tests/test_basic.py

@@ -277,6 +277,51 @@ class TestBasic(TestDemurrageDefault):
         self.assertEqual(r['status'], 1)
 
       
+    def test_approve(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 500)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+ 
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 600)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 0)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 600)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.increase_allowance(self.address, self.accounts[0], self.accounts[1], 200)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.decrease_allowance(self.address, self.accounts[0], self.accounts[1], 800)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.approve(self.address, self.accounts[0], self.accounts[1], 42)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
 
     def test_transfer_from(self):
         nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
@@ -315,6 +360,12 @@ class TestBasic(TestDemurrageDefault):
         balance = c.parse_balance_of(r)
         self.assertEqual(balance, 500)
 
+        (tx_hash, o) = c.transfer_from(self.address, self.accounts[2], self.accounts[1], self.accounts[3], 1)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
 
 if __name__ == '__main__':
     unittest.main()

python/tests/test_burn.py

@@ -0,0 +1,320 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+import datetime
+
+# external imports
+from chainlib.eth.constant import ZERO_ADDRESS
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+from chainlib.eth.block import (
+        block_latest,
+        block_by_number,
+    )
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+
+# test imports
+from erc20_demurrage_token.unittest.base import TestDemurrage
+
+logging.basicConfig(level=logging.INFO)
+logg = logging.getLogger()
+
+testdir = os.path.dirname(__file__)
+
+TAX_LEVEL = 2
+
+class TestBurn(TestDemurrage):
+
+    def setUp(self):
+        super(TestBurn, self).setUp()
+
+
+    def deploy(self, tax_level=None):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        self.mode = os.environ.get('ERC20_DEMURRAGE_TOKEN_TEST_MODE')
+        if self.mode == None:
+            self.mode = 'MultiNocap'
+        logg.debug('executing test setup default mode {}'.format(self.mode))
+
+        if tax_level != None:
+            self.deployer.settings.demurrage_level = tax_level * (10 ** 32)
+        self.deployer.settings.sink_address = self.accounts[9]
+        self.deployer.sink_address = self.accounts[9]
+        super(TestBurn, self).deploy(c, self.mode)
+
+        logg.info('deployed with mode {}'.format(self.mode))
+
+
+    # Burn tokens and immediately check balances and supply
+    def test_burn_basic(self):
+        self.deploy()
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], 1000000)
+        r = self.rpc.do(o)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[1], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.burn(self.address, self.accounts[1], 600000)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 0)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.add_minter(self.address, self.accounts[0], self.accounts[1])
+        r = self.rpc.do(o)
+
+        nonce_oracle = RPCNonceOracle(self.accounts[1], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.burn(self.address, self.accounts[1], 600000)
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        new_supply = c.parse_total_supply(r)
+        self.assertEqual(new_supply, 400000)
+
+        o = c.total_burned(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        burned = c.parse_total_burned(r)
+        self.assertEqual(burned, 600000)
+
+
+    # burn tokens and check sink balance and supply after first redistribution period
+    def test_burned_redistribution(self):
+        self.deploy()
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[0], 1000000000)
+        r = self.rpc.do(o)
+
+        (tx_hash, o) = c.burn(self.address, self.accounts[0], 500000000)
+        r = self.rpc.do(o)
+
+        (tx_hash, o) = c.transfer(self.address, self.accounts[0], self.sink_address, 500000000)
+        r = self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + self.period_seconds)
+
+        o = c.balance(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        bal = c.parse_balance(r)
+        self.assertEqual(bal, 416873881) # 9 periods demurrage
+
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        new_supply = c.parse_total_supply(r)
+        self.assertEqual(new_supply, 500000000)
+
+        o = c.balance(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        bal = c.parse_balance(r)
+        self.assert_within_lower(bal, 500000000, 0.0025)
+
+        self.backend.time_travel(self.start_time + (self.period_seconds * 2))
+
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        new_supply = c.parse_total_supply(r)
+        self.assertEqual(new_supply, 500000000)
+
+        # if we don't burn anything more it should be the same 
+        o = c.balance(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        bal = c.parse_balance(r)
+        self.assert_within_lower(bal, 500000000, 0.0025)
+
+
+    # burn tokens and check sink and taxed balance and supply after first redistribution period
+    def test_burned_other_redistribution(self):
+        self.deploy()
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[0], 1000000000)
+        r = self.rpc.do(o)
+
+        (tx_hash, o) = c.burn(self.address, self.accounts[0], 500000000)
+        r = self.rpc.do(o)
+
+        (tx_hash, o) = c.transfer(self.address, self.accounts[0], self.accounts[1], 500000000)
+        r = self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + self.period_seconds)
+
+        o = c.balance(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        bal = c.parse_balance(r)
+        self.assertEqual(bal, 416873881) # 9 periods demurrage
+
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        new_supply = c.parse_total_supply(r)
+        self.assertEqual(new_supply, 500000000)
+
+        o = c.balance(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        bal = c.parse_balance(r)
+        self.assertEqual(bal, 408536403) # 9 periods demurrage
+
+        o = c.balance(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        sink_bal = c.parse_balance(r)
+        self.assert_within_lower(sink_bal, 500000000 - 408536403, 0.09) # TODO is this ok variance, 1.0 is ppm?
+
+        self.backend.time_travel(self.start_time + (self.period_seconds * 2))
+
+        (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+        r = self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        new_supply = c.parse_total_supply(r)
+        self.assertEqual(new_supply, 500000000)
+
+        o = c.balance(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        next_bal = c.parse_balance(r)
+        self.assertEqual(next_bal, 333803985) # 9 periods demurrage
+
+        o = c.balance(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        prev_sink_bal = sink_bal
+        bal = prev_sink_bal + (bal - next_bal)
+        sink_bal = c.parse_balance(r)
+        self.assert_within_lower(sink_bal, bal, 0.09) # TODO is this ok variance, 1.0 is ppm?
+
+
+    # verify expected results of balance and supply after multiple redistribution periods
+    def test_burn_accumulate(self):
+        self.deploy(tax_level=2/1000)
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.add_minter(self.address, self.accounts[0], self.sink_address)
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.sink_address, self.default_supply)
+        r = self.rpc.do(o)
+
+        balance_share = int(self.default_supply / 2)
+        nonce_oracle = RPCNonceOracle(self.sink_address, self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+        (tx_hash, o) = c.transfer(self.address, self.sink_address, self.accounts[1], balance_share)
+        r = self.rpc.do(o)
+
+        new_supply = None
+        burn_rate = 1000
+        sink_bal = None
+        bob_bal = None
+        bob_refund = None
+
+        o = c.balance(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        bob_bal = c.parse_balance(r)
+        prev_bob_bal = bob_bal
+
+        iterations = 100
+
+        for i in range(1, iterations + 1):
+            nonce_oracle = RPCNonceOracle(self.sink_address, self.rpc)
+            c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+            if bob_refund != None:
+                (tx_hash, o) = c.transfer(self.address, self.sink_address, self.accounts[1], bob_refund)
+                r = self.rpc.do(o)
+                o = receipt(tx_hash)
+                r = self.rpc.do(o)
+                self.assertEqual(r['status'], 1)
+
+            (tx_hash, o) = c.burn(self.address, self.sink_address, burn_rate)
+            r = self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+
+            nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+            c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+            o = c.total_supply(self.address, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            new_supply = c.parse_total_supply(r)
+
+            self.backend.time_travel(self.start_time + (self.period_seconds * i))
+
+            (tx_hash, o) = c.change_period(self.address, self.accounts[0])
+            self.rpc.do(o)
+            
+            o = c.balance(self.address, self.accounts[1], sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            bob_bal = c.parse_balance(r)
+            bob_refund = prev_bob_bal - bob_bal
+
+            o = c.balance(self.address, self.sink_address, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            burner_bal = c.parse_balance(r)
+
+            sum_supply = bob_bal + burner_bal
+          
+            o = c.total_burned(self.address, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            total_burned = c.parse_balance(r)
+
+            o = c.to_base_amount(self.address, total_burned, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            total_burned_base = c.parse_balance(r)
+
+            expected_supply = self.default_supply - (burn_rate * i)
+            logg.info('checking burn round {} balance burner {} bob {} supply {} expected {} summed {} burned {} base {}'.format(i, burner_bal, bob_bal, new_supply, expected_supply, sum_supply, total_burned, total_burned_base))
+            self.assertEqual(new_supply, expected_supply)
+
+        sum_supply = burner_bal + bob_bal
+        logg.debug('balances sink {} bob {} total {} supply real {} original {}'.format(sink_bal, bob_bal, sum_supply, new_supply, self.default_supply))
+
+        self.assert_within_lower(sum_supply, new_supply, 0.00001)
+        self.assert_within_greater(burner_bal, balance_share - total_burned, 0.1)
+
+        bob_delta = self.default_supply * ((2 / 1000000) / 1000)
+        self.assert_within_lower(bob_bal, balance_share - bob_delta, 0.1)
+        
+        self.assertEqual(total_burned, iterations * burn_rate)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_demurrage.py

@@ -0,0 +1,133 @@
+# standard imports
+import datetime
+import unittest
+import logging
+import os
+
+# external imports
+from chainlib.eth.nonce import RPCNonceOracle
+from chainlib.eth.tx import receipt
+
+# local imports
+from erc20_demurrage_token import DemurrageToken
+from erc20_demurrage_token.demurrage import DemurrageCalculator
+
+# test imports
+from erc20_demurrage_token.unittest.base import TestDemurrage
+
+logging.basicConfig(level=logging.INFO)
+logg = logging.getLogger()
+
+
+class TestDemurragePeriods(TestDemurrage):
+
+    def setUp(self):
+        super(TestDemurragePeriods, self).setUp()
+   
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        self.mode = os.environ.get('ERC20_DEMURRAGE_TOKEN_TEST_MODE')
+        if self.mode == None:
+            self.mode = 'MultiNocap'
+        logg.debug('executing test setup default mode {}'.format(self.mode))
+
+        self.deployer.settings.demurrage_level = (2 / 1000) * (10 ** 32)
+        self.deployer.settings.sink_address = self.accounts[9]
+        self.deployer.sink_address = self.accounts[9]
+        self.deploy(c, self.mode)
+
+        logg.info('deployed with mode {}'.format(self.mode))
+
+
+    # verify that tax level calculation is in ppm as expected
+    def test_ppm(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], self.default_supply)
+        r = self.rpc.do(o)
+
+        self.backend.time_travel(self.start_time + 60)
+
+        (tx_hash, o) = c.apply_demurrage(self.address, self.accounts[0])
+        self.rpc.do(o)
+        o = receipt(tx_hash)
+        r = self.rpc.do(o)
+        self.assertEqual(r['status'], 1)
+
+        o = c.balance(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        bob_bal = c.parse_balance(r)
+
+        o = c.balance(self.address, self.sink_address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        sink_bal = c.parse_balance(r)
+
+        o = c.total_supply(self.address, sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        new_supply = c.parse_total_supply(r)
+
+        balance_delta = self.default_supply * ((2 / 1000000) / 1000) 
+        self.assertEqual(bob_bal, self.default_supply - balance_delta)
+
+
+
+    # verify balances and supply after multiple demurrage periods
+    def test_over_time(self):
+        nonce_oracle = RPCNonceOracle(self.accounts[0], self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[1], self.default_supply)
+        r = self.rpc.do(o)
+
+        o = c.balance(self.address, self.accounts[1], sender_address=self.accounts[0])
+        r = self.rpc.do(o)
+        bob_bal = c.parse_balance(r)
+        prev_bob_bal = bob_bal
+
+        nonce_oracle = RPCNonceOracle(self.sink_address, self.rpc)
+        c = DemurrageToken(self.chain_spec, signer=self.signer, nonce_oracle=nonce_oracle)
+
+        iterations = 100
+
+        for i in range(1, iterations + 1):
+            self.backend.time_travel(self.start_time + (self.period_seconds * i))
+
+            (tx_hash, o) = c.transfer(self.address, self.sink_address, self.accounts[1], prev_bob_bal - bob_bal)
+            r = self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+
+            (tx_hash, o) = c.apply_demurrage(self.address, self.sink_address)
+            self.rpc.do(o)
+            o = receipt(tx_hash)
+            r = self.rpc.do(o)
+            self.assertEqual(r['status'], 1)
+
+            o = c.balance(self.address, self.accounts[1], sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            bob_bal = c.parse_balance(r)
+
+            o = c.balance(self.address, self.sink_address, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            sink_bal = c.parse_balance(r)
+
+            o = c.total_supply(self.address, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            new_supply = c.parse_total_supply(r)
+
+            logg.info('round {} supply {} balance sink {} bob {}'.format(i, new_supply, sink_bal, bob_bal))
+
+        sum_supply = sink_bal + bob_bal
+
+        bob_delta = self.default_supply * ((2 / 1000000) / 100)
+
+        self.assert_within_lower(sum_supply, new_supply, 0.00001)
+        self.assert_within_greater(bob_bal, self.default_supply - bob_delta, 0.001)
+        self.assert_within_lower(sink_bal, bob_delta, 1000)
+        
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_redistribution_single.py

@@ -24,7 +24,7 @@ from erc20_demurrage_token import DemurrageToken
 # test imports
 from erc20_demurrage_token.unittest.base import TestDemurrageDefault
 
-logging.basicConfig(level=logging.DEBUG)
+logging.basicConfig(level=logging.INFO)
 logg = logging.getLogger()
 
 testdir = os.path.dirname(__file__)
@@ -88,18 +88,31 @@ class TestRedistribution(TestDemurrageDefault):
         (tx_hash, o) = c.mint_to(self.address, self.accounts[0], self.accounts[0], supply)
         self.rpc.do(o)
 
-        self.backend.time_travel(self.start_time + (self.period_seconds * 10))
+        self.backend.time_travel(self.start_time + (self.period_seconds * 100))
 
-        for i in range(1, 11):
+        balance_minter = None
-            logg.debug('checking period {}'.format(i))
+        balance_sink = None
+        real_supply = None
 
+        for i in range(1, 101):
             (tx_hash, o) = c.change_period(self.address, self.accounts[0])
             self.rpc.do(o)
             o = receipt(tx_hash)
             r = self.rpc.do(o)
             self.assertEqual(r['status'], 1)
 
-        i = 10
+            o = c.balance_of(self.address, self.sink_address, sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            balance_sink = c.parse_balance(r)
+
+            o = c.balance_of(self.address, self.accounts[0], sender_address=self.accounts[0])
+            r = self.rpc.do(o)
+            balance_minter = c.parse_balance(r)
+            
+            real_supply = balance_sink + balance_minter
+            logg.info('period {} testing sink {} mint {} adds up to supply {} of original {} (delta {})'.format(i, balance_sink, balance_minter, real_supply, supply, supply - real_supply))
+
+        i = 100
         o = c.redistributions(self.address, i, sender_address=self.accounts[0])
         redistribution = self.rpc.do(o)
 
@@ -122,7 +135,7 @@ class TestRedistribution(TestDemurrageDefault):
         r = self.rpc.do(o)
         balance_minter = c.parse_balance(r)
 
-        logg.debug('testing sink {} mint {} adds up to supply {} with demurrage between {} and {}'.format(balance_sink, balance_minter, supply, demurrage_previous, demurrage))
+        logg.debug('testing sink {} mint {} adds up to supply {} with demurrage between {} and {}'.format(balance_sink, balance_minter, real_supply, demurrage_previous, demurrage))
 
         self.assert_within_lower(balance_minter + balance_sink, supply, 0.001)
 

solidity/DemurrageTokenSingleNocap.sol

@@ -1,7 +1,6 @@
-pragma solidity > 0.6.11;
+pragma solidity >= 0.8.0;
 
 // SPDX-License-Identifier: GPL-3.0-or-later
-
 contract DemurrageTokenSingleCap {
 
 	// Redistribution bit field, with associated shifts and masks
@@ -12,7 +11,7 @@ contract DemurrageTokenSingleCap {
 	uint8 constant shiftRedistributionValue 	= 32;
 	uint256 constant maskRedistributionValue	= 0x00000000000000000000000000000000000000ffffffffffffffffff00000000; // ((1 << 72) - 1) << 32
 	uint8 constant shiftRedistributionDemurrage	= 104;
-	uint256 constant maskRedistributionDemurrage	= 0x0000000000ffffffffffffffffffffffffffff00000000000000000000000000; // ((1 << 20) - 1) << 140
+	uint256 constant maskRedistributionDemurrage	= 0x0000000000ffffffffffffffffffffffffffff00000000000000000000000000; // ((1 << 36) - 1) << 140
 
 	// Account balances
 	mapping (address => uint256) account;
@@ -38,7 +37,8 @@ contract DemurrageTokenSingleCap {
 	uint256 public decimals;
 
 	// Implements ERC20
-	uint256 public totalSupply;
+	//uint256 public totalSupply;
+	uint256 supply;
 
 	// Last executed period
 	uint256 public lastPeriod;
@@ -46,6 +46,9 @@ contract DemurrageTokenSingleCap {
 	// Last sink redistribution amount
 	uint256 public totalSink;
 
+	// Value of burnt tokens (burnt tokens do not decay)
+	uint256 public burned;
+
 	// 128 bit resolution of the demurrage divisor
 	// (this constant x 1000000 is contained within 128 bits)
 	uint256 constant nanoDivider = 100000000000000000000000000; // now nanodivider, 6 zeros less
@@ -95,6 +98,9 @@ contract DemurrageTokenSingleCap {
 	// Temporary event used in development, will be removed on prod
 	event Debug(bytes32 _foo);
 
+	// Emitted when tokens are burned
+	event Burn(address indexed _burner, uint256 _value);
+
 	// EIP173
 	event OwnershipTransferred(address indexed previousOwner, address indexed newOwner); // EIP173
 
@@ -206,7 +212,7 @@ contract DemurrageTokenSingleCap {
 
 		changePeriod();
 		baseAmount = toBaseAmount(_amount);
-		totalSupply += _amount;
+		supply += _amount;
 		increaseBaseBalance(_beneficiary, baseAmount);
 		emit Mint(msg.sender, _beneficiary, _amount);
 		saveRedistributionSupply();
@@ -249,7 +255,7 @@ contract DemurrageTokenSingleCap {
 		uint256 currentRedistribution;
 		uint256 grownSupply;
 
-		grownSupply = totalSupply;
+		grownSupply = totalSupply();
 		currentRedistribution = uint256(redistributions[redistributions.length-1]);
 		currentRedistribution &= (~maskRedistributionValue);
 		currentRedistribution |= (grownSupply << shiftRedistributionValue);
@@ -263,7 +269,7 @@ contract DemurrageTokenSingleCap {
 		return uint128((block.timestamp - periodStart) / periodDuration + 1);
 	}
 
-	// Add an entered demurrage period to the redistribution array
+	// Retrieve next redistribution if the period threshold has been crossed
 	function checkPeriod() private view returns (bytes32) {
 		bytes32 lastRedistribution;
 		uint256 currentPeriod;
@@ -349,14 +355,15 @@ contract DemurrageTokenSingleCap {
 	}
 
 	// Recalculate the demurrage modifier for the new period
+	// Note that the supply for the consecutive period will be taken at the time of code execution, and thus not necessarily at the time when the redistribution period threshold was crossed.
 	function changePeriod() public returns (bool) {
 		bytes32 currentRedistribution;
 		bytes32 nextRedistribution;
 		uint256 currentPeriod;
-		uint256 currentDemurrageAmount;
+		uint256 lastDemurrageAmount;
+		bytes32 lastRedistribution;
 		uint256 nextRedistributionDemurrage;
 		uint256 demurrageCounts;
-		uint256 periodTimestamp;
 		uint256 nextPeriod;
 
 		applyDemurrage();
@@ -365,20 +372,15 @@ contract DemurrageTokenSingleCap {
 			return false;
 		}
 
+		// calculate the decay from previous redistributino
+		lastRedistribution = redistributions[lastPeriod];
 		currentPeriod = toRedistributionPeriod(currentRedistribution);
 		nextPeriod = currentPeriod + 1;
-		periodTimestamp = getPeriodTimeDelta(currentPeriod);
+		lastDemurrageAmount = toRedistributionDemurrageModifier(lastRedistribution);
+		demurrageCounts = periodDuration / 60;
+		nextRedistributionDemurrage = decayBy(lastDemurrageAmount, demurrageCounts);
 	
-		currentDemurrageAmount = demurrageAmount; 
+		nextRedistribution = toRedistribution(0, nextRedistributionDemurrage, totalSupply(), nextPeriod);
-
-		demurrageCounts = demurrageCycles(periodTimestamp);
-		if (demurrageCounts > 0) {
-			nextRedistributionDemurrage = growBy(currentDemurrageAmount, demurrageCounts);
-		} else {
-			nextRedistributionDemurrage = currentDemurrageAmount;
-		}
-		
-		nextRedistribution = toRedistribution(0, nextRedistributionDemurrage, totalSupply, nextPeriod);
 		redistributions.push(nextRedistribution);
 
 		applyDefaultRedistribution(nextRedistribution);
@@ -423,14 +425,45 @@ contract DemurrageTokenSingleCap {
 	function approve(address _spender, uint256 _value) public returns (bool) {
 		uint256 baseValue;
 
+		if (allowance[msg.sender][_spender] > 0) {
+			require(_value == 0, 'ZERO_FIRST');
+		}
+		
 		changePeriod();
 
 		baseValue = toBaseAmount(_value);
-		allowance[msg.sender][_spender] += baseValue;
+		allowance[msg.sender][_spender] = baseValue;
 		emit Approval(msg.sender, _spender, _value);
 		return true;
 	}
 
+	// Reduce allowance by amount
+	function decreaseAllowance(address _spender, uint256 _value) public returns (bool) {
+		uint256 baseValue;
+
+		baseValue = toBaseAmount(_value);
+		require(allowance[msg.sender][_spender] >= baseValue);
+		
+		changePeriod();
+
+		allowance[msg.sender][_spender] -= baseValue;
+		emit Approval(msg.sender, _spender, allowance[msg.sender][_spender]);
+		return true;
+	}
+
+	// Increase allowance by amount
+	function increaseAllowance(address _spender, uint256 _value) public returns (bool) {
+		uint256 baseValue;
+
+		changePeriod();
+
+		baseValue = toBaseAmount(_value);
+
+		allowance[msg.sender][_spender] += baseValue;
+		emit Approval(msg.sender, _spender, allowance[msg.sender][_spender]);
+		return true;
+	}
+
 	// Implements ERC20, triggers tax and/or redistribution
 	function transfer(address _to, uint256 _value) public returns (bool) {
 		uint256 baseValue;
@@ -454,7 +487,9 @@ contract DemurrageTokenSingleCap {
 		baseValue = toBaseAmount(_value);
 		require(allowance[_from][msg.sender] >= baseValue);
 
+		allowance[_from][msg.sender] -= baseValue;
 		result = transferBase(_from, _to, baseValue);
+
 		emit Transfer(_from, _to, _value);
 		return result;
 	}
@@ -486,6 +521,29 @@ contract DemurrageTokenSingleCap {
 		emit OwnershipTransferred(oldOwner, owner);
 	}
 
+	// Explicitly and irretrievably burn tokens
+	// Only token minters can burn tokens
+	function burn(uint256 _value) public {
+		require(minter[msg.sender]);
+		require(_value <= account[msg.sender]);
+		uint256 _delta = toBaseAmount(_value);
+
+		applyDemurrage();
+		decreaseBaseBalance(msg.sender, _delta);
+		burned += _value;
+		emit Burn(msg.sender, _value);
+	}
+
+	// Implements ERC20
+	function totalSupply() public view returns (uint256) {
+		return supply - burned;
+	}
+
+	// Return total number of burned tokens
+	function totalBurned() public view returns (uint256) {
+		return burned;
+	}
+
 	// Implements EIP165
 	function supportsInterface(bytes4 _sum) public pure returns (bool) {
 		if (_sum == 0xc6bb4b70) { // ERC20

solidity/Makefile

@@ -33,6 +33,10 @@ test: all
 	python ../python/tests/test_pure.py
 
 install: all
+	#cp -v DemurrageToken*.{json,bin} ../python/erc20_demurrage_token/data/
+	cp -v DemurrageTokenSingleNocap.{json,bin} ../python/erc20_demurrage_token/data/
+
+install-broken: all
 	cp -v DemurrageToken*.{json,bin} ../python/erc20_demurrage_token/data/
 	
 .PHONY: test install