[+] Added StatementParser, [~] Restructured the Parsers

1 files changed, 70 insertions, 0 deletions

diff --git a/calculator-java/src/main/java/ch/bfh/parser/StatementParser.java b/calculator-java/src/main/java/ch/bfh/parser/StatementParser.java
new file mode 100644
index 0000000..c85398b
--- /dev/null
+++ b/calculator-java/src/main/java/ch/bfh/parser/StatementParser.java
@@ -0,0 +1,70 @@
+package ch.bfh.parser;
+
+import ch.bfh.CalculatorLexer;
+import ch.bfh.Token;
+import ch.bfh.exceptions.ParserException;
+
+public class StatementParser extends Parser{
+
+    String input;
+    ExpressionParser parsedExpression;
+
+    public void parseStatement(String input){
+        this.input = input;
+        cl = new CalculatorLexer();
+        cl.initLexer(input);
+        parsedExpression = null;
+        parse();
+    }
+
+    @Override
+    protected void parse() {
+        Token token = cl.nextToken();
+        String variableName = null;
+        lastToken = null;
+        loop:
+        while (token != null && token.type != Token.EOL) {
+            switch (token.type) {
+                case Token.LET:
+                    if (lastToken != null)
+                        throw new ParserException("The keyword 'let' cannot be placed anywhere else than at the beginning of an expression.");
+                    break;
+                case Token.EQU:
+                    if (lastToken == null || lastToken.type != Token.LET || variableName == null)
+                        throw new ParserException("The inputted token '=' can only be placed in a variable declaration context (let variable = Expression).");
+                    break;
+                case Token.END:
+                    if (lastToken != null)
+                        throw new ParserException("The keyword 'exit' cannot be placed anywhere else than at the beginning of an expression.");
+                    else
+                        System.exit(0);
+                case Token.ID:
+                    if (lastToken != null && lastToken.type == Token.LET && variableName == null) { // we are defining a new variable
+                        variableName = token.str;
+                        token = cl.nextToken();
+                        continue loop; // lastToken value will thus still be 'let' so that we could then parse the '=' token that is supposed to come next correctly.
+                    }else if (variableName != null && lastToken != null && lastToken.type != Token.EQU)
+                        throw new ParserException("Two consecutive variables ('"+variableName+"' and '"+token.str+"') were found in the declaration context.");
+                    // the expression started with a variable -> no definition -> meaning it is an expression
+                default:
+                    parsedExpression = new ExpressionParser(cl, token, false);
+                    if (lastToken != null && lastToken.type == Token.EQU) // this still need to be put in the variables list
+                        variables.put(variableName, parsedExpression);
+                    break;
+            }
+            lastToken = token;
+            token = cl.nextToken();
+        }
+        if (lastToken == null)
+            return;
+        if (lastToken.type == Token.LET || lastToken.type == Token.EQU)
+            throw new ParserException("Incomplete variable declaration");
+    }
+
+    @Override
+    public double getValue() {
+        if (parsedExpression == null)
+            return 0.0;
+        return parsedExpression.getValue();
+    }
+}
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