BCPL

基本组合编程语言（英语：Basic Combined Programming Language），是一种计算机程序设计语言，源自更早的CPL语言，1967年由剑桥大学的马丁·理察德所发展出来的^[1] 。

BCPL

编程范型	过程式，指令式，结构化
设计者	马丁·理察德
发行时间	1967年，​57年前​（1967）[1]
型态系统	无类型（所有东西都是字）
网站	www.cl.cam.ac.uk/~mr10/BCPL.html
启发语言
CPL
影响语言
B语言（间接影响C语言）

概述

Richards试着移除了CPL中最复杂的组成，第一支BCPL compiler在IBM 7094电脑中完成。身为早期编程语言的BCPL，如今已不再广泛使用，但它的影响却是深远的，今日流行的C语言即是参考BCPL所设计^[2]。BCPL被认定为第一个花括号编程语言（英语：Brace programming language）^[3]，作为BCPL后代语言，C语言使用花括号来表示块结构。

范例

下列是马丁查理斯的BCPL发行中的范例。

打印阶乘：

GET "LIBHDR"

LET START() = VALOF $(
    FOR I = 1 TO 5 DO
        WRITEF("%N! = %I4*N", I, FACT(I))
    RESULTIS 0
$)

AND FACT(N) = N = 0 -> 1, N * FACT(N - 1)

N个皇后问题：

GET "LIBHDR"

GLOBAL $(
    COUNT: 200
    ALL: 201
$)

LET TRY(LD, ROW, RD) BE
    TEST ROW = ALL THEN
        COUNT := COUNT + 1
    ELSE $(
        LET POSS = ALL & ~(LD | ROW | RD)
        UNTIL POSS = 0 DO $(
            LET P = POSS & -POSS
            POSS := POSS - P
            TRY(LD + P << 1, ROW + P, RD + P >> 1)
        $)
    $)

LET START() = VALOF $(
    ALL := 1
    FOR I = 1 TO 12 DO $(
        COUNT := 0
        TRY(0, 0, 0)
        WRITEF("%I2-QUEENS PROBLEM HAS %I5 SOLUTIONS*N", I, COUNT)
        ALL := 2 * ALL + 1
    $)
    RESULTIS 0
$)

引用

1. Martin Richards (2003 Computer Pioneer Award). IEEE Computer Society. [2017-11-24]. （原始内容存档于2017-11-24）.
2. Kernighan, Brian W. and Dennis M. Ritchie. The C Programming Language. Bell Telephone Laboratories. 1978: 2. ISBN 0-13-110163-3.
3. The BCPL Cintsys and Cintpos User Guide, 2.1.4 Section brackets (PDF). Historically BCPL used the symbols $( and $) to bracket commands and declarations. These symbols are called section brackets and are allowed to be followed by tags composed of letters, digits, dots and underlines. A tagged closing section bracket is forced to match with its corresponding open section bracket by the automatic insertion of extra closing brackets. Use of this mechanism is no longer recommended since it often leads to obscure programming errors. BCPL has been extended to allow all untagged section brackets to be replaced by { and } as appropriate.

参考文献

• Martin Richards, The BCPL Reference Manual (Memorandum M-352, Project MAC, Cambridge, July, 1967)
• Martin Richards, BCPL - a tool for compiler writing and systems programming (Proceedings of the Spring Joint Computer Conference, Vol 34, pp 557-566, 1969)
• Martin Richards, Arthur Evans, Robert F. Mabee, The BCPL Reference Manual (MAC TR-141, Project MAC, Cambridge, 1974)
• Martin Richards, C. Whitby-Strevens, BCPL, the language and its compiler (Cambridge University Press, 1980) ISBN 0-521-28681-6