Compilation Principle Dragon book chapter II A simple Arithmetic (+,-) translator implementation

Source: Internet
Author: User

Last night, I decided to work on the "compiling principle" of the frontal hard God lesson. the Dragon book.

Here is a simple arithmetic-type infix suffix of the translator.

This is also the Dragon book in a c implementation source code. Partially rewritten in C + +.

#include <iostream> #include <ctype.h> #include <stdlib.h> #include <stdio.h>using namespace Std;int lookahead;void Error ()//fault handling {    cout<< "error" <<endl;    Exit (1);} Token is used to match the pre-scan notation lookaheadvoid match (int t)//Detect iteration function {    if (lookahead = = t) {    lookahead = GetChar ();    }    else error ();} void term ()//Judgment function  isdigit (char c); Determines whether the input character is 0~9. is included in the header file <ctype.h>. {    if (isdigit (lookahead)) {        Putchar (lookahead);        Match (lookahead);    } else error ();} void expr () {term    ();    while (1)    {        if (lookahead = = ' + ') {            match (' + '), term ();p Utchar (' + ');        }        else if (lookahead = = '-') {            match (' + '); term ();p Utchar ('-');        }        else break;    }} int main () {    lookahead = GetChar ();    Expr ();    cout<<endl;    return 0;}

Compilation principle Dragon book chapter II A simple Arithmetic (+,-) translator implementation

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