eintr: lambda
C.4.3 A ‘lambda’ Expression: Useful Anonymity
---------------------------------------------
‘lambda’ is the symbol for an anonymous function, a function without a
name. Every time you use an anonymous function, you need to include its
whole body.
Thus,
(lambda (arg) (/ arg 50))
is a function that returns the value resulting from dividing whatever is
passed to it as ‘arg’ by 50.
Earlier, for example, we had a function ‘multiply-by-seven’; it
multiplied its argument by 7. This function is similar, except it
divides its argument by 50; and, it has no name. The anonymous
equivalent of ‘multiply-by-seven’ is:
(lambda (number) (* 7 number))
(
The ‘defun’ Macro defun.)
If we want to multiply 3 by 7, we can write:
(multiply-by-seven 3)
\_______________/ ^
| |
function argument
This expression returns 21.
Similarly, we can write:
((lambda (number) (* 7 number)) 3)
\____________________________/ ^
| |
anonymous function argument
If we want to divide 100 by 50, we can write:
((lambda (arg) (/ arg 50)) 100)
\______________________/ \_/
| |
anonymous function argument
This expression returns 2. The 100 is passed to the function, which
divides that number by 50.
Lambda Expressions (elisp)Lambda Expressions, for more about
‘lambda’. Lisp and lambda expressions derive from the Lambda Calculus.
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