From 36fb690d33b1f487a8d299470cfe9c5d900c58a3 Mon Sep 17 00:00:00 2001
From: Peter Wu <peter@lekensteyn.nl>
Date: Sun, 8 May 2016 16:01:51 +0200
Subject: Add skeleton for PicoRec

NAT and ID regexes were taken from RegexTest.java. Tests are added
before the implementation (test-driven development).
---
 src/PicoRec.java | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 src/PicoRec.java

(limited to 'src')

diff --git a/src/PicoRec.java b/src/PicoRec.java
new file mode 100644
index 0000000..eec2f38
--- /dev/null
+++ b/src/PicoRec.java
@@ -0,0 +1,72 @@
+/**
+ * Recognizer for the language described by grammar-ll1.txt.
+ */
+import dk.brics.automaton.RegExp;
+import dk.brics.automaton.RunAutomaton;
+
+public class PicoRec {
+
+    /** Regular expression describing the ID symbol. */
+    private final static String idRegex = "[a-z][a-z0-9]*";
+    /** Regular expression describing the NAT symbol. */
+    private final static String natRegex = "0|[1-9][0-9]*";
+
+    private final RunAutomaton idR, natR;
+
+    public PicoRec() {
+        idR = new RunAutomaton(new RegExp(idRegex).toAutomaton());
+        natR = new RunAutomaton(new RegExp(natRegex).toAutomaton());
+    }
+
+    /**
+     * Try to parse the input.
+     *
+     * @return true if the language is recognized, false otherwise.
+     */
+    public boolean parse(String text) {
+        // TODO implement this
+        return false;
+    }
+
+
+    /* Convenience functions for testing. */
+
+    private void check(String input, boolean expectOk) {
+        boolean accepted = parse(input);
+        System.out.println("Testing input: " + input);
+        if (expectOk && !accepted || !expectOk && accepted) {
+            throw new RuntimeException("Unexpected result for " + input);
+        }
+    }
+
+    private void check(String[] input, boolean expectOk) {
+        check(String.join("\n", input), expectOk);
+    }
+
+    private void assertOk(String... input) {
+        check(input, true);
+    }
+
+    private void assertFail(String... input) {
+        check(input, false);
+    }
+
+    public static void main(String[] args) {
+        PicoRec rec = new PicoRec();
+
+        // minimal program satisfying the language, without whitespace.
+        rec.assertOk("begindeclare|end");
+        // simple expression
+        rec.assertOk("begin declare a | a := 1 end");
+
+        // Trivial failures
+        rec.assertFail("");
+        rec.assertFail("begin");
+        rec.assertFail("begin declare");
+        rec.assertFail("begin declare |");
+        rec.assertFail("begin declare | end end");
+        rec.assertFail("begin declare end");
+        rec.assertFail("begin end");
+        rec.assertFail("end");
+    }
+}
-- 
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