mismatch (Function)

Syntax:

Arguments and Values:

Sequence-1—a sequence.

Sequence-2—a sequence.

from-end—a generalized boolean. The default is false.

test—a designator for a function of two arguments that returns a generalized boolean.

test-not—a designator for a function of two arguments that returns a generalized boolean.

start1, end1—bounding index designators of sequence-1. The defaults for start1 and end1 are 0 and nil, respectively.

start2, end2—bounding index designators of sequence-2. The defaults for start2 and end2 are 0 and nil, respectively.

key—a designator for a function of one argument, or nil.

position—a bounding index of sequence-1, or nil.

Description:

The specified subsequences of sequence-1 and sequence-2 are compared element-wise.

The key argument is used for both the sequence-1 and the sequence-2.

If sequence-1 and sequence-2 are of equal length and match in every element, the result is false. Otherwise, the result is a non-negative integer, the index within sequence-1 of the leftmost or rightmost position, depending on from-end, at which the two subsequences fail to match. If one subsequence is shorter than and a matching prefix of the other, the result is the index relative to sequence-1 beyond the last position tested.

If from-end is true, then one plus the index of the rightmost position in which the sequences differ is returned. In effect, the subsequences are aligned at their right-hand ends; then, the last elements are compared, the penultimate elements, and so on. The index returned is an index relative to sequence-1.

Examples:

 (mismatch "abcd" "ABCDE" :test #'char-equal) → 4
 (mismatch '(3 2 1 1 2 3) '(1 2 3) :from-end t) → 3
 (mismatch '(1 2 3) '(2 3 4) :test-not #'eq :key #'oddp) → NIL
 (mismatch '(1 2 3 4 5 6) '(3 4 5 6 7) :start1 2 :end2 4) → NIL

See Also:

Section 3.6 (Traversal Rules and Side Effects)

Notes:

The :test-not argument is deprecated.