fix: Fix EOF issues in Parser

Author: MarcellPerger1

src/main/java/net/marcellperger/mathexpr/interactive/Shell.java

@@ -5,13 +5,9 @@
 import net.marcellperger.mathexpr.parser.Parser;
 import net.marcellperger.mathexpr.util.Input;
 import net.marcellperger.mathexpr.util.MathUtil;
-import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.PrintStream;
-import java.util.Arrays;
-
-import static net.marcellperger.mathexpr.util.Input.input;
 
 public class Shell {
     Input in;
@@ -27,7 +23,6 @@ public static void main(String[] args) {
     }
 
     // TODO run() until exit better - parse exit command/Ctrl+C
-    // TODO fails badly with unchecked exception on parsing `12 + (`
 
     public void run() {
         //noinspection InfiniteLoopStatement

src/main/java/net/marcellperger/mathexpr/parser/ExprParseEofException.java

@@ -0,0 +1,18 @@
+package net.marcellperger.mathexpr.parser;
+
+public class ExprParseEofException extends ExprParseException {
+    public ExprParseEofException() {
+    }
+
+    public ExprParseEofException(String message) {
+        super(message);
+    }
+
+    public ExprParseEofException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public ExprParseEofException(Throwable cause) {
+        super(cause);
+    }
+}

src/main/java/net/marcellperger/mathexpr/parser/ExprParseException.java

@@ -1,7 +1,5 @@
 package net.marcellperger.mathexpr.parser;
 
-
-@SuppressWarnings("unused")  // I want all the constructors
 public class ExprParseException extends Exception {
     public ExprParseException() {
         super();

src/main/java/net/marcellperger/mathexpr/parser/Parser.java

@@ -53,7 +53,7 @@ public MathSymbol parseExpr() throws ExprParseException {
 
     public @NotNull MathSymbol parseParensOrLiteral() throws ExprParseException {
         discardWhitespace();
-        return peek() == '(' ? parseParens() : parseDoubleLiteral();
+        return peekExpect() == '(' ? parseParens() : parseDoubleLiteral();
     }
 
     public MathSymbol parseParens() throws ExprParseException {
@@ -115,21 +115,35 @@ protected CharSequence strFromHere() {
         return CharBuffer.wrap(src, idx, src.length());
     }
 
-    boolean notEof() {
+    public boolean notEof() {
         return idx < src.length();
     }
-    boolean isEof() {
+    public boolean isEof() {
         return idx >= src.length();
     }
 
-    char peek() {
+    protected char peekAssert() {
         return src.charAt(idx);
     }
-    char advance() {
+    protected char peekExpect() throws ExprParseEofException {
+        if(isEof()) throw new ExprParseEofException("Unexpected end of input");
+        return src.charAt(idx);
+    }
+    protected char advanceAssert() {
+        return src.charAt(idx++);
+    }
+    protected char advanceExpect() throws ExprParseEofException {
+        if(isEof()) throw new ExprParseEofException("Unexpected end of input");
         return src.charAt(idx++);
     }
-    boolean advanceIf(@NotNull Function<Character, Boolean> predicate) {
-        boolean doAdvance = predicate.apply(peek());
+    @SuppressWarnings("unused")
+    protected boolean advanceIf(@NotNull Function<Character, Boolean> predicate) throws ExprParseEofException {
+        boolean doAdvance = predicate.apply(peekExpect());
+        if(doAdvance) ++idx;
+        return doAdvance;
+    }
+    protected boolean advanceIfAssert(@NotNull Function<Character, Boolean> predicate) {
+        boolean doAdvance = predicate.apply(peekAssert());
         if(doAdvance) ++idx;
         return doAdvance;
     }
@@ -140,7 +154,7 @@ boolean advanceIf(@NotNull Function<Character, Boolean> predicate) {
      */
     protected int advanceWhile(@NotNull Function<Character, Boolean> predicate) {
         int n = 0;
-        while (notEof() && advanceIf(predicate)) ++n;
+        while (notEof() && advanceIfAssert(predicate)) ++n;
         return n;
     }
 
@@ -153,7 +167,7 @@ protected void discardWhitespace() {
     }
 
     protected void advanceExpectNext(char expected) throws ExprParseException {
-        char actual = advance();
+        char actual = advanceExpect();
         if(actual != expected) throw new ExprParseException("Expected '%c', got '%c'".formatted(expected, actual));
     }
     protected void advanceExpectNext_ignoreWs(char expected) throws ExprParseException {

src/main/java/net/marcellperger/mathexpr/util/MathUtil.java

@@ -5,6 +5,7 @@
 public class MathUtil {
     protected MathUtil() {}
 
+    // TODO this doesn't work: roundToSigFigs(1.22222 + 0.3, 10) == 1.5222200000000001
     public static double roundToSigFigs(double value, @Range(from=1, to=Integer.MAX_VALUE) int sigFigs) {
         int mostSignificantDigit = (int)Math.floor(Math.log10(value));
         int roundToDigit = mostSignificantDigit - sigFigs + 1;