可能是流传最广、最为经典的样板作品，Pascal语言之父、图灵奖获得者Niklaus Wirth在其名著Algorithms + Data Structures = Programs第5章给出的一个递归下降预测分析器实现。毫无疑问，它是用Pascal语言编写的。该编译器生成的目标语言是p-code，一台p- code虚拟机有3个寄存器（程序计数器、基本寄存器和栈顶寄存器）和8条指令（每条指令有多种形式）。-May be the most widely accepted model for the most classical works, Pascal language father, Turing Award winner Niklaus Wirth in his famous book Algorithms+ Data Structures = Programs Chapter 5 gives a recursive descent parser to achieve prediction. There is no doubt that it is written in Pascal. The compiler generates the target language is the p-code, a p-code virtual machine has three registers (program counter, the basic registers and stack registers) and 8 instructions (each instruction takes many forms).