怎么在ABAP里用函数式编程思想打印出非波拉契Fibonacci

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！

在ABAP里也有很多种方式实现这个需求。

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 ichanging 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 ichanging 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 fibonacciIMPORTING !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| ) )ELSEVALUE #( 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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