---
title: Global Functions
---
CashScript has several built-in functions for things like cryptographic and arithmetic applications, and it includes many common arithmetic and other operators that you would expect in a programming language.
## Arithmetic functions
### abs()
```solidity
int abs(int a)
```
Returns the absolute value of argument `a`.
### min()
```solidity
int min(int a, int b)
```
Returns the minimum value of arguments `a` and `b`.
### max()
```solidity
int max(int a, int b)
```
Returns the maximum value of arguments `a` and `b`.
### within()
```solidity
bool within(int x, int lower, int upper)
```
Returns `true` if and only if `x >= lower && x < upper`.
## Hashing functions
### ripemd160()
```solidity
bytes20 ripemd160(any x)
```
Returns the RIPEMD-160 hash of argument `x`.
### sha1()
```solidity
bytes20 sha1(any x)
```
Returns the SHA-1 hash of argument `x`.
### sha256()
```solidity
bytes32 sha256(any x)
```
Returns the SHA-256 hash of argument `x`.
### hash160()
```solidity
bytes20 hash160(any x)
```
Returns the RIPEMD-160 hash of the SHA-256 hash of argument `x`.
### hash256()
```solidity
bytes32 hash256(any x)
```
Returns the double SHA-256 hash of argument `x`.
## Signature checking functions
:::caution
All signature checking functions must comply with the [NULLFAIL][bip146] rule which only allows `0x` as an invalid signature — any other invalid signature will **immediately fail** the entire script.
:::
#### Nullfail example
The `NULLFAIL` rule means passing an invalid signature to `checkSig()` does not return `false` — it fails the script. To safely return `false` on a signature check, use an empty `0x` signature instead, as shown below:
```solidity
// this script will immediately fail
// because userSig will be invalid for either the 'seller' or the 'referee'
require(checkSig(userSig, seller) || checkSig(userSig, referee));
// instead, use 2 different signatures
// set the unused signature to 0x so 'checkSig' returns false
require(checkSig(sellerSig, seller) || checkSig(userSig, referee));
```
### checkSig()
```solidity
bool checksig(sig s, pubkey pk)
```
Checks that transaction signature `s` is valid for the current transaction and matches with public key `pk`.
### checkMultiSig()
```solidity
bool checkMultiSig(sig[] sigs, pubkey[] pks)
```
Performs a multi-signature check using a list of transaction signatures and public keys.
:::note
While this function can be used inside your smart contracts, it is not supported by the TypeScript SDK, so it is recommended not to use it. Instead a `checkMultiSig()` call can be simulated using multiple `checkSig()` calls.
:::
### checkDataSig()
```solidity
bool checkDataSig(datasig s, bytes msg, pubkey pk)
```
Checks that sig `s` is a valid signature for message `msg` and matches with public key `pk`.
[bip146]: https://github.com/bitcoin/bips/blob/master/bip-0146.mediawiki
