basicInterpreter1.01 支持分支语句
2024-09-06 08:39:03
源码：https://files.cnblogs.com/files/heyang78/basicInterpreter-20200531-1.rar
输入：
count=
print(count)
if count== then print("count等于10")
if count< then print("count小于20")
if count> then print("count大于5")
print("程序结束")
输出：
原文=count= print(count) if count== then print("count等于10") if count< then print("count小于20") if count> then print("count大于5") print("程序结束")
Index Type No Text Type Desc
------------------------------------------------------------------------------------
count Variable
= =
Number
print Function
( (
count Variable
) )
if if
count Variable
== ==
Number
then then
print Function
( (
"count等于10" String
) )
if if
count Variable
< then
Number
then then
print Function
( (
"count小于20" String
) )
if if
count Variable
> >
Number
then then
print Function
( (
"count大于5" String
) )
print Function
( (
"程序结束" String
) )
执行结果:
"count等于10"
"count小于20"
"count大于5"
"程序结束"
核心代码：
Token：
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_ASSIGN=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
public static final int TYPE_EQUAL=8; // ==
public static final int TYPE_IF=9; // if
public static final int TYPE_THEN=10; // then
public static final int TYPE_LESSTHAN=10; // <
public static final int TYPE_BIGGERTHAN=11; // >
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_ASSIGN) {
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";
}else if(type==TYPE_EQUAL) {
return "==";
}else if(type==TYPE_IF) {
return "if";
}else if(type==TYPE_THEN) {
return "then";
}else if(type==TYPE_LESSTHAN) {
return "<";
}else if(type==TYPE_BIGGERTHAN) {
return ">";
}
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：
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 text) {
tokens = new ArrayList<Token>(); String swallowed = "";
for (int i = 0; i < text.length(); i++) {
char c = text.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_BIGGERTHAN));
}else if (c == '<') {
addTextToList(swallowed);
swallowed=""; tokens.add(new Token(c, Token.TYPE_LESSTHAN));
} else if (c == '=') {
int next=i+1;
if(next<text.length() && text.charAt(next)=='=') {
// ==
addTextToList(swallowed);
swallowed="";
tokens.add(new Token("==",Token.TYPE_EQUAL));
i++;
}else {
// =
addTextToList(swallowed);
swallowed="";
tokens.add(new Token(c, Token.TYPE_ASSIGN));
}
} else if(c == '\"') {
addTextToList(swallowed);
swallowed=""; int idx=i+1; while(idx<text.length()) {
char cEnd = text.charAt(idx); if (cEnd == '\"') {
break;
} idx++;
} String sub=text.substring(i, idx+1);
tokens.add(new Token(sub, Token.TYPE_STRING));
i=idx;
} else {
swallowed += c;
}
} setTokenIndexes();
} private void addTextToList(String text) {
if("if".equalsIgnoreCase(text)) {
tokens.add(new Token(text, Token.TYPE_IF));
}else if("then".equalsIgnoreCase(text)) {
tokens.add(new Token(text, Token.TYPE_THEN));
}else 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：
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_ASSIGN) {
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.");
}
}
}
}else if(token.getType()==Token.TYPE_IF) {
int vLeft,vRight;
String oprand; // get left value
token=fetchToken();
if(token.getType()==Token.TYPE_VARIABLE) {
String varibleName=token.getText(); if(varmap.containsKey(varibleName)) {
vLeft=varmap.get(varibleName);
}else {
throw new Exception("Variable:'"+varibleName+"' was not assigned.");
}
}else if(token.getType()==Token.TYPE_NUMBER) {
vLeft=Integer.parseInt(token.getText());
}else {
throw new Exception("Expected:number/variable actual:"+token.getText()+" "+token);
} // get ==,<,>
token=fetchToken();
if(token.getType()!=Token.TYPE_EQUAL && token.getType()!=Token.TYPE_LESSTHAN && token.getType()!=Token.TYPE_BIGGERTHAN) {
throw new Exception("Expected:'== or > or <' actual:"+token.getText()+" "+token);
}
oprand=token.getText(); // get right
token=fetchToken();
if(token.getType()==Token.TYPE_VARIABLE) {
String varibleName=token.getText(); if(varmap.containsKey(varibleName)) {
vRight=varmap.get(varibleName);
}else {
throw new Exception("Variable:'"+varibleName+"' was not assigned.");
}
}else if(token.getType()==Token.TYPE_NUMBER) {
vRight=Integer.parseInt(token.getText());
}else {
throw new Exception("Expected:number/variable actual:"+token.getText()+" "+token);
} // Compare
if(compare(vLeft,oprand,vRight)) {
// get then
token=fetchToken();
if(token.getType()!=Token.TYPE_THEN) {
throw new Exception("Expected:'then' actual:"+token.getText()+" "+token);
}
}else {
// 跳过两个token(then及后面的dosth)
fetchToken();
fetchToken();
}
}
}
} private boolean compare(int vLeft,String oprand,int vRight) throws Exception{
if("==".equals(oprand)) {
return vLeft==vRight;
}else if(">".equals(oprand)) {
return vLeft>vRight;
}else if("<".equals(oprand)) {
return vLeft<vRight;
}else {
throw new Exception("oprand should be == or > or < but not.");
}
} 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--;
}
}
}
--2020年5月31日--
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