| ▲ | diath 2 days ago |
| out (; balance == balance + amount) // checked after method returns
How exactly does it work? Is this a typo? |
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| ▲ | prydt 2 days ago | parent | next [-] |
| Looks like its a typo :( The correct way to go about this would be to return the new balance and capture the return value in the first part of the out postcondition like: ```D
double deposit(double amount)
in (amount > 0, "Deposit amount must be positive")
out (result; result == balance)
{
balance += amount;
return balance;
}
``` My mistake! https://dlang.org/spec/function.html#postconditions |
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| ▲ | Jtsummers 2 days ago | parent [-] | | HN does not use markdown code block formatting so this is hard to read. Formatting code blocks is simple, two blank spaces before any line to make it a code block and no need for extra newlines (unlike between paragraphs): double deposit(double amount)
in (amount > 0, "Deposit amount must be positive")
out (result; result == balance)
{
balance += amount;
return balance;
}
|
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| ▲ | lgas 2 days ago | parent | prev [-] |
| I've never used D, but it appears to be valid syntax. https://dlang.org/spec/function.html#postconditions |
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| ▲ | diath 2 days ago | parent | next [-] | | I'm not asking about the syntax, I'm asking about the logic where a value can be equal to itself plus another value when the pre-condition is that it must be > 0. | |
| ▲ | prydt 2 days ago | parent | prev [-] | | The syntax is correct but I made a logical error since balance is being compared to itself (as opposed to the new balance at the end). |
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