源码下载：https://files.cnblogs.com/files/heyang78/basicInterpreter-20200529-1.rar
脚本：
count=
print(count)
count=
print(count)
print(cnt)
print("Hello!Interpreter!")
说明：
count=10 赋值语句，变量count赋值为10，变量count不需定义
print(count) 打印变量count里的值
count=20 赋值语句，变量count赋值为20
print(count) 打印变量count里的值
print(cnt) 打印变量cnt里的值
print("Hello!Interpreter!") 打印字符串"Hello!Interpreter!"
执行结果：
原文=count= print(count) count= print(count) print(cnt) print("Hello!Interpreter!")
Index Type No Text Type Desc
------------------------------------------------------------------------------------
count Variable
= =
Number
print Function
( (
count Variable
) )
count Variable
= =
Number
print Function
( (
count Variable
) )
print Function
( (
cnt Variable
) )
print Function
( (
"Hello!Interpreter!" String
) )
执行结果:
Variable:'cnt' was not assigned.
"Hello!Interpreter!"
核心程序：
Token类：
package com.heyang;
public class Token {
public static final int TYPE_OPEN_PARENTHESIS=0; // (
public static final int TYPE_CLOSE_PARENTHESIS=1; // (
public static final int TYPE_EQUAL=2; // =
public static final int TYPE_NUMBER=4; // \d+
public static final int TYPE_STRING=5; // \w+
public static final int TYPE_VARIABLE=6; // Variable
public static final int TYPE_FUNCTION=7; // Function
private int type;
private String text;
private int index;// Used to remember location
public Token(char c,int type) {
this.text=String.valueOf(c);
this.type=type;
}
public Token(String word,int type) {
this.text=word;
this.type=type;
}
public String toString() {
return String.format("token(text=%s,type=%s,index=%d)", text,getTypeStr(),index);
}
public String getTypeStr() {
if(type==TYPE_OPEN_PARENTHESIS) {
return "(";
}else if(type==TYPE_CLOSE_PARENTHESIS) {
return ")";
}else if(type==TYPE_EQUAL) {
return "=";
}else if(type==TYPE_NUMBER) {
return "Number";
}else if(type==TYPE_STRING) {
return "String";
}else if(type==TYPE_VARIABLE) {
return "Variable";
}else if(type==TYPE_FUNCTION) {
return "Function";
}
return null;
}
public int getType() {
return type;
}
public void setType(int type) {
this.type = type;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
public int getIndex() {
return index;
}
public void setIndex(int index) {
this.index = index;
}
}
Lexer类：
package com.heyang; import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.regex.Pattern; /**
* Parse json string to tokens
* @author Heyang
*
*/
public class Lexer {
private List<Token> tokens; public Lexer(String jsonTxt) {
tokens = new ArrayList<Token>(); String swallowed = "";
for (int i = 0; i < jsonTxt.length(); i++) {
char c = jsonTxt.charAt(i); if (Character.isWhitespace(c)) {
addTextToList(swallowed);
swallowed="";
continue;
} else if (c == '(') {
addTextToList(swallowed);
swallowed=""; tokens.add(new Token(c, Token.TYPE_OPEN_PARENTHESIS));
} else if (c == ')') {
addTextToList(swallowed);
swallowed=""; tokens.add(new Token(c, Token.TYPE_CLOSE_PARENTHESIS));
} else if (c == '=') {
addTextToList(swallowed);
swallowed=""; tokens.add(new Token(c, Token.TYPE_EQUAL));
} else if(c == '\"') {
addTextToList(swallowed);
swallowed=""; int idx=i+1; while(idx<jsonTxt.length()) {
char cEnd = jsonTxt.charAt(idx); if (cEnd == '\"') {
break;
} idx++;
} String sub=jsonTxt.substring(i, idx+1);
tokens.add(new Token(sub, Token.TYPE_STRING));
i=idx;
} else {
swallowed += c;
}
} setTokenIndexes();
} private void addTextToList(String text) {
if(isFunction(text)) {
tokens.add(new Token(text, Token.TYPE_FUNCTION));
}else if(isNumber(text)) {
tokens.add(new Token(text, Token.TYPE_NUMBER));
}else if(isVarable(text)) {
tokens.add(new Token(text, Token.TYPE_VARIABLE));
}
} private boolean isFunction(String text) {
if("print".equalsIgnoreCase(text)) {
return true;
} return false;
} private boolean isNumber(String code) {
final String patternStr = "\\d+";
return Pattern.matches(patternStr, code);
} private boolean isVarable(String code) {
final String patternStr = "([a-zA-Z_])\\w*";
return Pattern.matches(patternStr, code);
} public void printTokens() {
final String continuousStar = createRepeatedStr("-", 84);
final String layout = "%-20s %-20s %-20s %-20s %s";
StringBuilder sb = new StringBuilder(); sb.append(String.format(layout, "Index", "Type No","Text","Type Desc","\n"));
sb.append(continuousStar + "\n");
int index=0;
for(Token token:tokens) {
sb.append(String.format(layout, String.valueOf(index),String.valueOf(token.getType()), token.getText(),token.getTypeStr(),"\n"));
index++;
} System.out.println(sb.toString());
} private static String createRepeatedStr(String seed, int n) {
return String.join("", Collections.nCopies(n, seed));
} public void setTokenIndexes() {
int idx = 0;
for (Token t : tokens) {
idx++;
t.setIndex(idx);
}
} public String getCompactJsonTxt() {
StringBuilder sb=new StringBuilder(); for (Token t : tokens) {
sb.append(t.getText());
} return sb.toString();
} public List<Token> getTokenList() {
return tokens;
}
}
Interpreter类：
package com.heyang; import java.util.HashMap;
import java.util.List;
import java.util.Map; public class Interpreter {
private List<Token> tokens;
private int tokenIdx; public Interpreter(List<Token> tokens) throws Exception{
this.tokens=tokens;
this.tokenIdx=0; execute();
} private void execute() throws Exception{
Map<String,Integer> varmap=new HashMap<String,Integer>();
Token token;
for(;;) {
token=fetchToken();
if(token==null) {
return;
} if(token.getType()==Token.TYPE_VARIABLE) {
String varibleName=token.getText(); token=fetchToken();
if(token.getType()==Token.TYPE_EQUAL) {
token=fetchToken(); if(token.getType()==Token.TYPE_NUMBER) {
int variableValue=Integer.parseInt(token.getText()); // 赋值核心语句
varmap.put(varibleName, variableValue);
}
}else {
throw new Exception("Expected:'=' actual:"+token.getText()+" "+token);
}
}else if(token.getType()==Token.TYPE_FUNCTION) {
String functionName=token.getText(); if("print".equalsIgnoreCase(functionName)) {
token=fetchToken();
if(token.getType()!=Token.TYPE_OPEN_PARENTHESIS) {
throw new Exception("Expected:'(' actual:"+token.getText()+" "+token);
} token=fetchToken();
if(token.getType()==Token.TYPE_STRING) {
// 打印字符串
String str=token.getText();
System.out.println(str);
}else if(token.getType()==Token.TYPE_VARIABLE) {
String varibleName=token.getText(); // 打印变量
if(varmap.containsKey(varibleName)) {
int value=varmap.get(varibleName);
System.out.println(value);
}else {
System.out.println("Variable:'"+varibleName+"' was not assigned.");
}
}
}
}
}
} private Token fetchToken() {
if(tokenIdx>=tokens.size()) {
return null;
}else {
Token t=tokens.get(tokenIdx);
tokenIdx++;
return t;
}
} private void returnToken() {
if(tokenIdx>0) {
tokenIdx--;
}
}
}
整合：
package com.heyang; import com.heyang.util.BracketChecker;
import com.heyang.util.CommonUtil;
import com.heyang.util.Renderer; public class EntryPoint {
public static void main(String[] args) {
try {
// Read context from file
String text=CommonUtil.readTextFromFile("C:\\hy\\files\\basic\\01.basic");
System.out.println("原文="+text); // Is brackets balanced
BracketChecker checker=new BracketChecker();
boolean isBalanced=checker.isBalanced(text);
if(isBalanced==false) {
System.out.println(Renderer.paintBrown(checker.getErrMsg()));
return;
} // lex text to tokens
Lexer lex=new Lexer(text);
lex.printTokens(); // Execute
System.out.println("执行结果:\n");
new Interpreter(lex.getTokenList());
}catch(Exception ex) {
System.out.println(Renderer.paintBrown(ex.getMessage()));
ex.printStackTrace();
}
}
}
感慨：在《Java编程艺术》的指引下，解释器的第一步踏出了。
--2020年5月29日--