系统编程工具REXX和CLIST.ppt

Diagnostic函数 Sourceline() - Returns number of lines of code, or actual line of source code Condition() - Returns information depending on one of four arguments (C(condition), D(descriptive), I(instruction) and S(status)) Errortext() - Return text of REXX error message associated with argument number REXX special variable sigl - Assigned with line number where condition trap error occurred 测试 测试的数量取决于可能的最终用户规模 开始用少量数据测试 测试代码的所有部分 从错误中测试可恢复性 Use REXX aids to confirm the program flow - Trace instruction Trace指令 REXX Trace指令- 有用的选项: Trace R – “Results” – most useful Trace N – “Normal” – traces negative return codes Trace O – “Off” – turns tracing off Trace I – Intermediates – most information 其它Trace选项: - A, C, E, F, L, S, ?, !, +n, -n Trace - 不修改代码 - TSO命令 EXECUTIL TS – 运行可执行程序之前 REXX Trace()函数: - trace_actions_in_effect = Trace() 交互式调试 Trace ? 在每个指令处停止: - Press enter to continue - type “=” to re-execute last clause - type anything else – like REXXTRY – process line immediately Trace n – skip n pause (n is a whole number) 其他调试工具 Attention mode(PA1) immediate commands - HE – halt execution - HI – halt interpretation - TS – trace start - TE – trace end - HT – halt typing - RT – resume typing 数据栈(Stack) Data stack stores data: stack or queue Stack = LIFO (Last In First Out) Queue = FIFO (Last In First Out) The data stack can be treated as a stack: the last element added to the stack is the first removed (LIFO). Alternatively, you may treat it as queue: first element added to the stack is the first removed (FIFO). Data Stack的使用 三个基本指令 　- PUSH – put one item of data on top of stack - QUEUE – put item on bottom of stack - PULL – remove item from top of stack 空栈 You read data from the top of the stack with PULL keyword instruction. Note that this removes (or destroys) the data (unlike variable access). Unfortunately, when the stack is empty, REXX will expect to find input data from the terminal