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mismatch sequence-1 sequence-2 &key from-end test test-not key start1 start2 end1 end2

=> position

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.


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.


 (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 

Side Effects: None.

Affected By: None.

Exceptional Situations: None.

See Also:

Section 3.6 (Traversal Rules and Side Effects)


The :test-not argument is deprecated.

The following X3J13 cleanup issues, not part of the specification, apply to this section:

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