Compilation principle Syntax analysis Experiment (Java Implementation)

Import Java.util.stack;public class LL1 {//Add sync symbol ll (1) Parse table private String [] analysistable = new string[][]{{"TZ", "" "" " , "TZ", "Synch", "Synch"},{"", "+tz", "", "", "ε", "ε"},{"FY", "Synch", "", "FY", "Synch", "Synch"},{"", "ε", "*fy", "", "ε", "ε "},{" I "," Synch "," Synch "," (E) "," Synch "," Synch "}};//store Terminator private String [] VT = new string[]{" I "," + "," * "," (",") "," # " };//store Terminator private string [] VN = new string[]{"E", "Z", "T", "Y", "F"};//input string private StringBuilder Strtoken = new StringBuilder (") i*+i");//analysis stack private stack<string> stack = new stack<string> ();//a save an input symbol read from the input string, the current symbol private String a  = null;//x holds stack stack top symbol private String X = Null;//flag Flag Predictive Analysis succeeded private Boolean flag = true;//Record the position of the current character in the input string private int cur = 0;//record steps private int count = 0;//initialize protected void init () {strtoken.append ("#"); Stack.push ("#"); System.out.printf ("%-9s%-38s%6s%-20s\n", "step", "Symbol stack", "Input string", "used production"), Stack.push ("E"); Curcharacter (); System.out.printf ("%-6d%-20s%6s \ n", count,stack.tostring (), strtoken.substring (cur, STRTOKEN.LEngth ()));} Reads the current stack top symbol protected String Stackpeek () {X = Stack.peek (); return X;} Returns the letter of the current position in the input string, private String Curcharacter () {a = String.valueof (Strtoken.charat (cur)); return A;} Determine if X is Terminator protected Boolean XISVT () {for (int i = 0; i < (vt.length-1); i++) {if (Vt[i].equals (X)) {return true;}} return false;} Find X in non-terminator analysis table protected String VNTI () {int Ni = 0, Tj = 0;for (int i = 0; i < vn.length; i++) {if (Vn[i].equals (X)) {Ni = i;}} for (int j = 0; J < Vt.length; J + +) {if (Vt[j].equals (a)) {Tj = j;}} return ANALYSISTABLE[NI][TJ];} Judge M[a,a]={x->x1x2 ... xk}//put x1x2 ... XK Propulsion Stack//x1x2 ... xk=ε, do not push anything into the stack protected Boolean productiontype () {if (VNTI ()! = "") {return true;} return false;} Advance stack stack protected void Pushstack () {stack.pop (); String M = VNTI (); String ch;for (int i = (m.length ()-1), I >= 0; i--) {ch = string.valueof (M.charat (i)); Stack.push (ch);} System.out.printf ("%-6d%-20s%6s%-1s->%-12s\n", (++count), stack.tostring (), strtoken.substring (cur, Strtoken.length ()), x,m);} Master control program protected void toTalcontrolprogram () {while (flag = = True) {Stackpeek (); if (XISVT () = = True) {if (X.equals (a)) {cur++;a = Curcharacter (); Stack.pop (); System.out.printf ("%-6d%-20s%6s \ n", (++count), stack.tostring (), strtoken.substring (cur, strtoken.length ()));} Else{error ();}} else if (X.equals ("#")) {if (X.equals (a)) {flag = false;} Else{error ();}} else if (productiontype () = = True) {if (VNTI (). Equals ("synch")) {ERROR ();} else if (VNTI (). Equals ("ε")) {Stack.pop (); System.out.printf ("%-6d%-20s%6s%-1s->%-12s\n", (++count), stack.tostring (), strtoken.substring (cur, Strtoken.length ()), X,vnti ());} Else{pushstack ();}} Else{error ();}}} Error protected void error () {System.out.println ("An error occurred in the input string, unable to parse"); System.exit (0);} Print Storage analysis table protected void printf () {if (flag = = False) {System.out.println ("======== parse succeeded");} else {System.out.println ("======== analysis Failed");}} public static void Main (string[] args) {LL1 ll1 = new LL1 (); Ll1.init (); Ll1.totalcontrolprogram (); ll1.printf ();}}

Test Data 1:i*i+i

Test result 1:

Step        symbol Stack                                      input string  using the resulting formula               0      [#, E]               i*i+i# 1      [#, Z, T]            i*i+i# e->tz          2      [#, Z, Y, F]         i*i+i# t->fy          3      [#, Z, y, i]         i*i+i# f->i           4      [#, Z, y]             *i+i# 5      [#, Z, y, F, *]       *i+i# y->*fy         6      [#, Z, y, F]           i+i# 7      [#, Z, y, i]           i+i# f->i           8      [#, Z, y]
   
    +i# 9 [#,      z]                  +i# y->ε     [#, Z, T, +]            +i# z->+tz one     [#, Z, T]                i#     [#, Z, Y, F]             i# T->fy [#     , Z, y, i]             i# f->i     [#, Z, y]                 #     [#, z]                    # y->ε     [#]                       # z->ε           ======== Analysis Success
   

Test Data 2:) i*+i

Test Result 2:

Step        symbol Stack                                      input string  using the resulting formula               0      [#, E]               ) i*+i# input string error, unable to parse

Compilation principle Syntax analysis Experiment (Java Implementation)