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Macro INCF, DECF

Syntax

  • incf place [delta-form]new-value
  • decf place [delta-form]new-value

Arguments and Values

  • place - a place.
  • delta-form - a form; evaluated to produce a delta. The default is 1.
  • delta - a number.
  • new-value - a number.

Description

incf and decf are used for incrementing and decrementing the value of place, respectively.

The delta is added to (in the case of incf) or subtracted from (in the case of decf) the number in place and the result is stored in place.

Any necessary type conversions are performed automatically.

For information about the evaluation of subforms of places, see section {\secref\GenRefSubFormEval}.

Examples

(defparameter *n* 0) *n* (incf n)

1

*n*

1

(decf *n* 3)

-2

*n*

-2

(decf *n* -5)

3

(decf *n*)

2

(incf *n* 0.5)

2.5

(decf *n*)

1.5

*n*

1.5

Side Effects

place is modified.

Affected By

None.

Exceptional Situations

None.

See Also

Notes

None.

\issue{PUSH-EVALUATION-ORDER:FIRST-ITEM}