LISP—运算符

运算符是一个符号,它告诉编译器执行特定的数学或逻辑操作。 LISP允许在众多的数据业务,通过各种函数,宏和其他结构的支持。

允许对数据的操作都可以归类为:

  • 算术运算

  • 比较操作

  • 逻辑运算

  • 位运算

算术运算

下表列出了所有支持的LISP算术运算符。假设变量A=10和变量B=20则:

运算符 描述 Example
+ 增加了两个操作数 (+ A B) = 30
从第一数减去第二个操作数 (- A B)= -10
* 乘两个操作数 (* A B) = 200
/ 通过取消分子除以分子 (/ B A) = 2
mod,rem 模运算符和其余整数除法后 (mod B A ) = 0
incf 递增运算符,所指定的第二个参数增加整数值 (incf A 3) = 13
decf 递减操作符,通过指定的第二个参数减小整数值 (decf A 4) = 9

例子

创建一个名为main.lisp一个新的源代码文件,并在其中输入如下代码:

(setq a 10)
(setq b 20)
(format t "~% A + B = ~d" (+ a b))
(format t "~% A - B = ~d" (- a b))
(format t "~% A x B = ~d" (* a b))
(format t "~% B / A = ~d" (/ b a))
(format t "~% Increment A by 3 = ~d" (incf a 3))
(format t "~% Decrement A by 4 = ~d" (decf a 4))

当您单击Execute按钮,或按下Ctrl+ E,LISP立即执行它,返回的结果是:

A + B = 30
A - B = -10
A x B = 200
B / A = 2
Increment A by 3 = 13
Decrement A by 4 = 9

比较操作

下表列出了所有支持的LISP关系运算符的数字之间进行比较。然而不像其他语言的关系运算符,LISP的比较操作符可能需要超过两个操作数,他们在只有数字工作。

假设变量A=10和变量B=20,则:

Operator 描述 Example
= 检查如果操作数的值都相等与否,如果是的话那么条件为真。 (= A B)= true.
/= 检查如果操作数的值都不同,或没有,如果值不相等,则条件为真。 (/= A B) =true.
> 检查如果操作数的值单调递减。 (> A B) !=true.
< 检查如果操作数的值单调递增。 (< A B) = true.
>= 如有左操作数的值大于或等于下一个右操作数的值,如果是则条件检查为真。 (>= A B) !=true.
<= 如有左操作数的值小于或等于其右操作数的值,如果是,则条件检查为真。 (<= A B) = true.
max 它比较两个或多个参数,并返回最大值。 (max A B) 返回20
min 它比较两个或多个参数,并返回最小值。 (min A B) 返回 20

示例

创建一个名为main.lisp一个新的源代码文件,并在其中输入如下代码:

(setq a 10)
(setq b 20)
(format t "~% A = B is ~a" (= a b))
(format t "~% A /= B is ~a" (/= a b))
(format t "~% A > B is ~a" (> a b))
(format t "~% A < B is ~a" (< a b))
(format t "~% A >= B is ~a" (>= a b))
(format t "~% A <= B is ~a" (<= a b))
(format t "~% Max of A and B is ~d" (max a b))
(format t "~% Min of A and B is ~d" (min a b))

当您单击Execute按钮,或按下Ctrl+ E,LISP立即执行它,返回的结果是:

A = B is NIL
A /= B is T
A > B is NIL
A < B is T
A >= B is NIL
A <= B is T
Max of A and B is 20
Min of A and B is 10

布尔值逻辑操作

Common Lisp中提供了三种逻辑运算符:AND,OR,而不是运算符的布尔值。假定A=nil,B=5,那么

运算符 描述 示例
and 这需要任意数量的参数。该参数是从左向右计算。如果所有参数的计算结果为非零,那么最后一个参数的值返回。否则就返回nil。 (and A B) = NIL.
or 这需要任意数量的参数。该参数是从左向右计算的,直到一个计算结果为非零,则此情况下返回参数值,否则返回nil。 (or A B) = 5.
not 它接受一个参数,并返回t,如果参数的计算结果为nil。 (not A) = T.

示例

创建一个名为main.lisp一个新的源代码文件,并在其中输入如下代码:

(setq a 10)
(setq b 20)
(format t "~% A and B is ~a" (and a b))
(format t "~% A or B is ~a" (or a b))
(format t "~% not A is ~a" (not a))
(terpri)
(setq a nil)
(setq b 5)
(format t "~% A and B is ~a" (and a b))
(format t "~% A or B is ~a" (or a b))
(format t "~% not A is ~a" (not a))
(terpri)
(setq a nil)
(setq b 0)
(format t "~% A and B is ~a" (and a b))
(format t "~% A or B is ~a" (or a b))
(format t "~% not A is ~a" (not a))
(terpri)
(setq a 10)
(setq b 0)
(setq c 30)
(setq d 40)
(format t "~% Result of and operation on 10, 0, 30, 40 is ~a" (and a b c d))
(format t "~% Result of and operation on 10, 0, 30, 40 is ~a" (or a b c d))
(terpri)
(setq a 10)
(setq b 20)
(setq c nil)
(setq d 40)
(format t "~% Result of and operation on 10, 20, nil, 40 is ~a" (and a b c d))
(format t "~% Result of and operation on 10, 20, nil, 40 is ~a" (or a b c d))

当您单击Execute按钮,或按下Ctrl+ E,LISP立即执行它,返回的结果是:

A and B is 20
A or B is 10
not A is NIL

A and B is NIL
A or B is 5
not A is T

A and B is NIL
A or B is 0
not A is T

Result of and operation on 10, 0, 30, 40 is 40
Result of and operation on 10, 0, 30, 40 is 10

Result of and operation on 10, 20, nil, 40 is NIL
Result of and operation on 10, 20, nil, 40 is 10

请注意,逻辑运算工作,布尔值,其次,数字为零,NIL不是一样的。

对数位运算

位运算符位工作并进行逐位操作。对于按位与,或,和XOR运算的真值表如下:

p q p and q p or q p xor q
0 0 0 0 0
0 1 0 1 1
1 1 1 1 0
1 0 0 1 1
Assume if A = 60; and B = 13; now in binary format they will be as follows:
A = 0011 1100
B = 0000 1101
-----------------
A and B = 0000 1100
A or B = 0011 1101
A xor B = 0011 0001
not A  = 1100 0011

通过LISP支持位运算符列于下表中。假设变量A=60和变量B=13,则:

操作符 描述 Example
logand 这将返回位逻辑的参数和。如果没有给出参数,则结果为-1,这是该操作的标识。 (logand a b)) = 12
logior 这将返回位逻辑包括它的参数或。如果没有给出参数,那么结果是零,这是该操作的标识。 (logior a b) = 61
logxor 这将返回其参数的按位逻辑异或。如果没有给出参数,那么结果是零,这是该操作的标识。 (logxor a b) = 49
lognor 这不返回的逐位它的参数。如果没有给出参数,则结果为-1,这是该操作的标识。 (lognor a b) = -62,
logeqv 这将返回其参数的逐位逻辑相等(也称为异或非)。如果没有给出参数,则结果为-1,这是该操作的标识。 (logeqv a b) = -50

示例

创建一个名为main.lisp一个新的源代码文件,并在其中输入如下代码:

 
 
(setq a 60)
(setq b 13)
(format t "~% BITWISE AND of a and b is ~a" (logand a b))
(format t "~% BITWISE INCLUSIVE OR of a and b is ~a" (logior a b))
(format t "~% BITWISE EXCLUSIVE OR of a and b is ~a" (logxor a b))
(format t "~% A NOT B is ~a" (lognor a b))
(format t "~% A EQUIVALANCE B is ~a" (logeqv a b))
(terpri)
(terpri)
(setq a 10)
(setq b 0)
(setq c 30)
(setq d 40)
(format t "~% Result of bitwise and operation on 10, 0, 30, 40 is ~a" (logand a b c d))
(format t "~% Result of bitwise or operation on 10, 0, 30, 40 is ~a" (logior a b c d))
(format t "~% Result of bitwise xor operation on 10, 0, 30, 40 is ~a" (logxor a b c d))
(format t "~% Result of bitwise eqivalance operation on 10, 0, 30, 40 is ~a" (logeqv a b c d))

当您单击Execute按钮,或按下Ctrl+ E,LISP立即执行它,返回的结果是:

BITWISE AND of a and b is 12
BITWISE INCLUSIVE OR of a and b is 61
BITWISE EXCLUSIVE OR of a and b is 49
A NOT B is -62
A EQUIVALANCE B is -50


Result of bitwise and operation on 10, 0, 30, 40 is 0
Result of bitwise or operation on 10, 0, 30, 40 is 62
Result of bitwise xor operation on 10, 0, 30, 40 is 60
Result of bitwise eqivalance operation on 10, 0, 30, 40 is -61
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