小编给大家分享一下怎么在ABAP里用函数式编程思想打印出非波拉契Fibonacci,相信大部分人都还不怎么了解,因此分享这篇文章给大家参考一下,希望大家阅读完这篇文章后大有收获,下面让我们一起去了解一下吧!
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下面这个report分别用递归和ABAP internal table的方式实现了非波拉契数列的打印。
REPORT Z_FIBO. PARAMETERS: N type i, v1 RADIOBUTTON GROUP v default 'X', v2 RADIOBUTTON GROUP v. data: f type i, t type i. data: product_guid type comm_product-product_guid. get run time field t.case 'X'. when v1\. perform fibonacci using n changing f. when v2\. perform fibonacci_2 using n changing f. endcase. write: / 'Fibonacci(', n, ') =', f. get run time field t. write: / 'Runtime', t, 'microseconds'. *&---------------------------------------------------------------------* *& Form fibonacci *&---------------------------------------------------------------------* form fibonacci using in type i changing fib type i. data: f_1 type i, f_2 type i, n_1 type i, n_2 type i.case in. when 0\. fib = 1. when 1\. fib = 1. when others. n_1 = in - 1. n_2 = in - 2. perform fibonacci using n_1 changing f_1. perform fibonacci using n_2 changing f_2. fib = f_1 + f_2. endcase. endform. "fibonacci *&---------------------------------------------------------------------* *& Form fibonacci_2 *&---------------------------------------------------------------------* form fibonacci_2 using in type i changing fib type i. data: f_1 type i, f_2 type i, n_1 type i, n_2 type i, l type i. data: fibo type table of i. append 1 to fibo. " fibonacci(0) append 1 to fibo. " fibonacci(1) n_1 = 1. n_2 = 2. l = in - 1. do l times. read table fibo index n_1 into f_1. read table fibo index n_2 into f_2. fib = f_1 + f_2. add 1 to n_1\. add 1 to n_2. append fib to fibo. enddo. endform. "fibonacci_2
以上两种解决方案相对来说都比较传统,再来看看使用ABAP 7.40提供的新关键字COND实现的非波拉契数列打印:
REPORT z.CLASS lcl_fibonacci DEFINITION. PUBLIC SECTION. TYPES: zint_tab TYPE TABLE OF int4 WITH EMPTY KEY. METHODS fibonacci IMPORTING !n TYPE i RETURNING VALUE(fib_numbers) TYPE zint_tab. ENDCLASS.CLASS lcl_fibonacci IMPLEMENTATION. METHOD fibonacci. fib_numbers = COND #( WHEN n = 0THEN VALUE #( ( |0| ) )WHEN n = 1THEN VALUE #( ( |0| ) ( |1| ) )ELSE VALUE #( LET fn1 = fibonacci( n - 1 )x = fn1[ lines( fn1 ) ] y = fn1[ lines( fn1 ) - 1 ] IN ( LINES OF fn1 ) ( x + y ) ) ). ENDMETHOD. ENDCLASS. START-OF-SELECTION. cl_demo_output=>display( NEW lcl_fibonacci( )->fibonacci( 10 ) ).
打印输出:
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