Lambda calculus codifies the correct way to do these substitutions. Given that y = x−1 is a valid rearrangement of the second equation, this: λ y = x−1 means a function substituting the symbols x−1 for the symbol y. Now imagine applying λ y to each term in the first equation. If a term is y then perform the substitution; otherwise do ...
Here is another really good reference which explains very well what are lambda expressions in C++: Microsoft.com: Lambda expressions in C++. I especially like how well it explains the parts of a lambda expression, in particular: the capture clause, parameter list, trailing-return-type, and lambda body.
I saw some examples using built-in functions like sorted, sum etc. that use key=lambda. What does lambda mean here? How does it work? For the general computer science concept of a lambda, see What...
The lambda construct is a shorter way to define a simple function that calculates a single expression. The def statement can be inconvenient and make the code longer, broken up and harder to read through.
Lambda functions are most useful in things like callback functions, or places in which you need a throwaway function. JAB's example is perfect - It would be better accompanied by the keyword argument key, but it still provides useful information.
by_attribute = lambda x: x.attribute == value xs = filter(by_attribute , xs) Yes, that's two lines of code instead of one, but you clean filter expression from cumbersome lambda and by naming lambda nicely it literally becomes being read as "filter by attribute" :)
An easy way to perform an if in lambda is by using list comprehension. You can't raise an exception in lambda, but this is a way in Python 3.x to do something close to your example:
LAMBDA Overview There are three key pieces of =LAMBDA to understand: LAMBDA function components Naming a lambda Calling a lambda function LAMBDA function components Let’s look at an example which creates a basic lambda function. Suppose we have the following formula: =LAMBDA(x, x+122) In this, x is the argument you can pass in when calling the LAMBDA, and x+122 is the logic. For example ...
Lambda expressions are becoming popular in other languages (like C#) as well. They're not going anywhere. Reading up on closures would be a useful exercise to understand Lambdas. Closures make a lot of coding magic possible in frameworks like jQuery.
Lambda is a means of creating an anonymous function or closure. In imperative languages (and functional ones) it is equivalent to allowing nested functions where the inner function has access to local variable and parameters of the enclosing function.
