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Ethereum: How Multiplication and Division Work in Solidity
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In Solidity, the order of operations is crucial for accurate calculations. Two common arithmetic operations that can cause confusion are multiplication and division. In this article, we’ll explore how these operations work in Solidity, focusing specifically on how they are calculated.
Precedence and Order of Operations
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Solidity follows a specific precedence rule when it comes to arithmetic operations:
- Parentheses: Expressions in parentheses are evaluated first.
- Exponents (e.g. **): All exponents are evaluated next.
- Multiplication and division (e.g. 2 * 3): The order is multiplication before division.
- Addition and subtraction (e.g. 5 + 3): The order is addition before subtraction.
Let’s look at the example you gave:
Amount = (15-10) 10 / 15 (10000 - 5000) / 10000;
When we decompose this expression, we can follow the precedence rules:
- Evaluate expressions in parentheses:
(15-10)
and(10000 - 5000)
15-10 = 5
(exponentiation not applicable)
10000 - 5000 = 5000
(exponentiation not applicable)
- Multiply
5
by10
:5 * 10 = 50
- Divide
50
by15
:50 / 15 = 3.333...
(division is not exact due to floating point arithmetic)
- Finally, multiply the result by
(5000 / 10000)
:(3.333...) * (5) = 16.666...
The correct So calculation should be: actually be:
Amount = 50 / 15 * 5000 / 10000;
Not 5 * 10 / 15
.
Common mistakes
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How to avoid common mistakes when working with arithmetic operations in Solidity:
- Always evaluate expressions in parentheses first.
- Pay attention to exponents (e.g. **) and make sure you perform the operation correctly.
- Use floating point arithmetic when dividing to avoid problems due to integer division.
Best practices
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How to write accurate and efficient Solidity code:
- Use parentheses to group operations for clarity.
- Follow the precedence rules carefully.
- Be careful with exponentiation (e.g. **) when doing calculations with large numbers or exponential growth.
Understanding how multiplication and division work in Solidity will help you write more accurate and reliable smart contracts that take advantage of the language’s unique features.