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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 137 |
1 files changed, 136 insertions, 1 deletions
@@ -5631,14 +5631,149 @@ Examples: (flatten '(((()) ()))) -> nil -.SS Functions memq and memqual +.SS Functions memq, memql and memqual + +.TP +Syntax: + +(memq <object> <list>) +(memql <object> <list>) +(memqual <object> <list>) + +.TP +Description: + +The memq, memql and memqual functions search the <list> for a member +which is, respectively, eq, eql or equal to <object>. (See the eq, eql and +equal functions below.) + +If no such element found, nil is returned. + +Otherwise, that tail of the list is returned whose first element +is the matching object. .SS Function tree-find +.TP Syntax: +(tree-find <obj> <tree> <test-function>) + +.TP Description: + +The tree-find function searches <tree> for an occurence of <obj>. Tree can be +any atom, or a cons. If <tree> it is a cons, it is understood to be a proper +list whose elements are also trees. + +The equivalence test is performed by <test-function> which must take two +arguments, and has conventions similar to eq, eql or equal. + +tree-find works as follows. If <tree> is equivalent to <obj> under +<test-function>, then t is returned to announce a successful finding. +If this test fails, and <tree> is an atom, nil is returned immediately to +indicate that the find failed. Otherwise, <tree> is taken to be a proper list, +and tree-find is recursively applied to each element of the list in turn, using +the same <obj> and <test-function> arguments, stopping at the first element +which returns non-nil. + .SS Function some, all and none +.TP Syntax: + +(some <list> <predicate-fun> <key-fun>) +(all <list> <predicate-fun> <key-fun>) +(none <list> <predicate-fun> <key-fun>) + +.TP Description + +The some, all and none functions apply a predicate test over a list of +elements. The elements of <list> are reduced to values using <key-fun>, which +is a one-argument function. If <key-fun> is specified as nil, then (fun +identity) is substituted, and thus the values of the list are taken as they +are. + +These functions have short-circuiting semantics and return conventions similar +to the and and or operators. + +The some function applies <predicate-fun> to successive values +produced by retrieving elements of <list> and processing them through +<key-fun>. If the list is empty, it returns nil. Otherwise it returns the +first non-nil return value returned by a call to <predicate-fun> and +stops evaluating more elements. If <predicate-fun> returns nil for all +elements, it returns nil. + +The all function applies <predicate-fun> to successive values +produced by retrieving elements of <list> and processing them through +<key-fun>. If the list is empty, it returns t. Otherwise, if +<predicate-fun> yields nil for any value, the all function immediately +returns without invoking <predicate-fun> on any more elements. +If all the elements are processed, then the all function returns +the value which <predicate-fun> yielded for the last element. + +The none function applies <predicate-fun> to successive values +produced by retrieving elements of <list> and processing them through +<key-fun>. If the list is empty, it returns t. Otherwise, if +<predicate-fun> yields non-nil for any value, the none function +immediately returns nil. If <predicate-fun> yields nil for all +values, the none function returns t. + +.TP +Examples: + +;; some of the integers are odd +(some (fun oddp) '(2 4 6 9) nil) -> t + +;; none of the integers are even +(none (fun evenp) '(1 3 4 7) nil) -> t + .SS Functions eq, eql and equal +.TP +Syntax: + +(eq <left-obj> <right-obj>) +(eql <left-obj> <right-obj>) +(equal <left-obj> <right-obj>) + +.TP +Description: + +The principal equality test functions eq, eql and equal test whether +two objects are equivalent, using different criteria. They return t +if the objects are equivalent, and nil otherwise. + +The eq function uses the strictest equivalence test, called implementation +equality. The eq function returns t if, and only if, <left-obj> and +<right-obj> are actually the same object. The eq test is is implemented +by comparing the raw bit pattern of the value, whether or not it is +an immediate value or a pointer to a heaped object, including its type +tags. Consequently, two objects of different type are never equal, two +character values are eq if they are the same character, and two fixnum integers +are eq if they have the same value. All other objects kinds are actually +represented as pointers, and are eq if they point to the same object in memory. +So two bignum integers might not be eq even if they have the same numeric +value, two lists might not be eq even if all their corresponding elements are +eq, two strings might not be eq even if they hold identical text, etc. + +The eql function is slightly less strict than eq. The difference between +eql and eq is that if <left-obj> and <right-obj> are bignums which have +the same numeric value, eql returns t, even if they are different objects. +For all other objects, eql behaves like eq. + +The equal function is less strict than eql. In general, it recurses into some +kinds of aggregate objects to perform a structural equivalence. If <left-obj> +and <right-obj> are eql then they are also equal. If the two objects are both +cons cells, then they are equal if their "car" fields are equal and their "cdr" +fields are equal. If two objects are vectors, they are equal if they have the +same length, and their corresponding elements are equal. If two objects are +strings, they are equal if they are textually identical. If two objects are +functions, they are equal if they have equal environments, and if they have +equal functions. Two compiled functions are the same if they are the same +function. Two interpreted functions are equal if their list structure is equal. + +For some aggregate objects, there is no special semantics. Two hashes, +symbols, packages, or streams are equal if they are the same hash. + +Certain object types have a custom equal function. + .SS Arithmetic functions +, -, *, trunc, mod, expt, sqrt .SS Arithmetic function exptmod |