118 lines
3.2 KiB
Java
118 lines
3.2 KiB
Java
package serene.simple;
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import java.io.EOFException;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.InputStreamReader;
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import java.io.PushbackReader;
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import java.util.ArrayList;
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import java.util.List;
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public class Reader {
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public static Node readNode(PushbackReader inputStream) throws IOException {
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char c = (char) inputStream.read();
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inputStream.unread(c);
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if (c == '(') {
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return readList(inputStream);
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}
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else if (Character.isDigit(c)) {
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return readNumber(inputStream);
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}
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else if (c == ')') {
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throw new IllegalArgumentException("Unmatch paranthesis.");
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}
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else {
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return readSymbol(inputStream);
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}
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}
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public static ListNode<Node> read(InputStream inputStream) throws IOException {
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return read(new PushbackReader(new InputStreamReader(inputStream)));
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}
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public static ListNode<Node> read(PushbackReader inputStream) throws IOException {
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List<Node> nodes = new ArrayList<Node>();
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skipWhiteSpaces(inputStream);
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char c = (char) inputStream.read();
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while ((byte) c != -1) {
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inputStream.unread(c);
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nodes.add(readNode(inputStream));
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skipWhiteSpaces(inputStream);
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c = (char) inputStream.read();
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}
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return ListNode.list(nodes);
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}
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private static Node readList(PushbackReader inputStream) throws IOException {
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char opening = (char) inputStream.read();
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assert opening == '(' : "Lists must start with a '('";
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List<Node> nodes = new ArrayList<Node>();
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do {
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skipWhiteSpaces(inputStream);
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char c = (char) inputStream.read();
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if (c == ')') {
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break;
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} else if ((byte) c == -1) {
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throw new EOFException("EOF reached before closing of list");
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} else {
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inputStream.unread(c);
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nodes.add(readNode(inputStream));
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}
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} while(true);
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return SpecialForm.check(ListNode.list(nodes));
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}
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private static Node readSymbol(PushbackReader inputStream) throws IOException {
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String str = "";
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while (true) {
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int ch = inputStream.read();
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if(isWhiteSpace(ch)) {
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inputStream.unread(ch);
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break;
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};
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str = str + (char) ch;
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}
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return new SymbolNode(str);
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}
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private static Node readNumber(PushbackReader inputStream) throws IOException {
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String number = "";
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while (true) {
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int ch = inputStream.read();
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if(isWhiteSpace(ch)) {
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inputStream.unread(ch);
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break;
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};
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number = number + (char) ch;
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}
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return new NumberNode(Long.parseLong(number, 10));
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}
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private static void skipWhiteSpaces(PushbackReader inputStream) throws IOException {
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int ch = inputStream.read();
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while (isWhiteSpace(ch)) {
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ch = inputStream.read();
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}
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inputStream.unread(ch);
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}
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private static boolean isWhiteSpace(int ch) {
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return (ch == ' ' || ch == '\t' || ch == '\f' || ch == '\r' || ch == '\n');
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}
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}
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