What does "Call-by-Name" mean?
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Call-by-name is a way to evaluate expressions in programming languages. In this approach, the program does not evaluate an expression until its value is actually needed. This means that if a value is not used, it does not get calculated at all.
How It Works
When using call-by-name, whenever a function is called, the arguments are passed without being evaluated first. If the function uses the argument, then it gets evaluated at that moment. If the argument is not used in the function, it prevents any unnecessary computations.
Benefits
One main advantage of call-by-name is that it can save time and resources. If an expression is complex and not always needed, it won't waste effort in computing its value. This makes the program potentially quicker and more efficient in certain cases.
Downsides
However, call-by-name can also lead to some problems. If the argument has side effects, meaning it does things beyond just returning a value, these effects may happen multiple times if the argument is used several times in the function. This can make the program behave in unexpected ways.
Comparison with Call-by-Value
Call-by-name is often contrasted with call-by-value. In call-by-value, arguments are evaluated before being passed to a function. This can be more straightforward but may also do more work than necessary if some values are never used.