defsetf

defsetf( 
s_accessFn 
s_updateFn 
)
=> setf_<s_accessFn>

Description

defsetf is a macro that allows you to specify an update function to use when setf() is called with a place using a given access function. It creates a macro with the prefix setf_ which is used by setf to update a value at the place given by s_accessFn().

Arguments

s_accessFn	The access function name which setf is expected to handle.
s_updateFn	The name of a function or macro which replaces the value at the place accessed by s_accessFn. The function or macro must accept the same number of arguments as s_accessFn plus one additional argument containing the new value.

Value Returned

setf_<s_accessFn>
	A macro which is used in setf.

Examples

; a personal CAR function to distinguish from the built-in car

defun(CAR (x) car(x))

; update function which replaces the car of the list with a new value

defun(SETCAR (x new)

  car(rplaca(x new))

)

defsetf(CAR SETCAR)

test_ls='(1 2 3 4 5 6)

; use := operator which is equivalent to setf()

CAR(test_ls) := 10

assert(test_ls == '(10 2 3 4 5 6))

Related Topics

Function and Program Structure

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