Editing Scheme (programming language) (section)

===Equivalence predicates===
{{See also|relational operator}}
Scheme has three different types of equivalence between arbitrary objects denoted by three different ''equivalence predicates'', relational operators for testing equality, <code>eq?</code>, <code>eqv?</code> and <code>equal?</code>:
*  <code>eq?</code> evaluates to <code>#f</code> unless its parameters represent the same data object in memory;
* <code>eqv?</code> is generally the same as <code>eq?</code> but treats primitive objects (e.g. characters and numbers) specially so that numbers that represent the same value are <code>eqv?</code> even if they do not refer to the same object;
* <code>equal?</code> compares data structures such as lists, vectors and strings to determine if they have congruent structure and <code>eqv?</code> contents.(R5RS sec. 6.1)<ref name="r5rs"/>

Type dependent equivalence operations also exist in Scheme: <code>string=?</code> and <code>string-ci=?</code> compare two strings (the latter performs a case-independent comparison); <code>char=?</code> and <code>char-ci=?</code> compare characters; <code>=</code> compares numbers.<ref name="r5rs"/>