From a87d5f76858a58766ff9fae5d42aba4d6baf0aad Mon Sep 17 00:00:00 2001
From: aNNiMON <annimon119@gmail.com>
Date: Sat, 16 Sep 2023 20:13:27 +0300
Subject: [PATCH] Added floating number scientific notation

---
 .../com/annimon/ownlang/parser/Lexer.java     | 32 +++++++++++++++++++
 .../com/annimon/ownlang/parser/LexerTest.java | 13 ++++++++
 .../parser/LexerValidDataProvider.java        |  6 ++--
 3 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/Lexer.java b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/Lexer.java
index 48efd15..d4af633 100644
--- a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/Lexer.java
+++ b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/Lexer.java
@@ -164,6 +164,10 @@ public final class Lexer {
             if (current == '.') {
                 if (hasDot) throw error("Invalid float number " + buffer);
                 hasDot = true;
+            } else if (current == 'e' || current == 'E') {
+                int exp = subTokenizeScientificNumber();
+                buffer.append(current).append(exp);
+                break;
             } else if (!Character.isDigit(current)) {
                 break;
             }
@@ -172,6 +176,34 @@ public final class Lexer {
         }
         addToken(TokenType.NUMBER, buffer.toString(), startPos);
     }
+
+    private int subTokenizeScientificNumber() {
+        int sign = 1;
+        switch (next()) {
+            case '-': sign = -1;
+            case '+': skip(); break;
+        }
+
+        boolean hasValue = false;
+        char current = peek(0);
+        while (current == '0') {
+            hasValue = true;
+            current = next();
+        }
+        int result = 0;
+        int position = 0;
+        while (Character.isDigit(current)) {
+            result = result * 10 + (current - '0');
+            current = next();
+            position++;
+        }
+        if (position == 0 && !hasValue) throw error("Empty floating point exponent");
+        if (position >= 4) {
+            if (sign > 0) throw error("Float number too large");
+            else throw error("Float number too small");
+        }
+        return sign * result;
+    }
     
     private void tokenizeHexNumber(int skipChars) {
         clearBuffer();
diff --git a/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerTest.java b/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerTest.java
index c3e9785..92b39c9 100644
--- a/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerTest.java
+++ b/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerTest.java
@@ -26,6 +26,9 @@ public class LexerTest {
     public static Stream<Arguments> invalidData() {
         return Stream.<Arguments>builder()
                 .add(Arguments.of("Wrong float point", "3.14.15"))
+                .add(Arguments.of("Empty float exponent", "3e"))
+                .add(Arguments.of("Float number too small", "3e-00009000"))
+                .add(Arguments.of("Float number too large", "3e+00009000"))
                 .add(Arguments.of("Wrong HEX number", "0Xf7_p6_s5"))
                 .add(Arguments.of("HEX number ends with _", "0Xf7_"))
                 .add(Arguments.of("Empty rest of HEX number", "#"))
@@ -46,6 +49,16 @@ public class LexerTest {
                 .extracting(Token::text)
                 .containsExactly("0", "3.1415", "CAFEBABE", "f7d6c5", "FFFF");
     }
+
+    @Test
+    public void testFloatNumbersExponent() {
+        String input = "4e+7 0.3E-19 2e0 5e0000000000000200 5E-000000089";
+        List<Token> result = Lexer.tokenize(input);
+        assertThat(result)
+                .allMatch(t -> t.type().equals(NUMBER))
+                .extracting(Token::text)
+                .containsExactly("4e7", "0.3E-19", "2e0", "5e200", "5E-89");
+    }
     
     @Test
     public void testString() {
diff --git a/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerValidDataProvider.java b/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerValidDataProvider.java
index 5c0390c..c90cb44 100644
--- a/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerValidDataProvider.java
+++ b/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerValidDataProvider.java
@@ -25,6 +25,9 @@ public class LexerValidDataProvider {
                 Arguments.of("Numbers",
                         "12 7.8 90000000 10.03",
                         List.of(NUMBER, NUMBER, NUMBER, NUMBER)),
+                Arguments.of("Float notation",
+                        "7e8",
+                        List.of(NUMBER)),
                 Arguments.of("Hex numbers",
                         "#FF 0xCA 0x12fb 0xFF",
                         List.of(HEX_NUMBER, HEX_NUMBER, HEX_NUMBER, HEX_NUMBER))
@@ -80,9 +83,6 @@ public class LexerValidDataProvider {
 
     private static List<Arguments> notSupported() {
         return List.of(
-                Arguments.of("Float notation",
-                        "7e8",
-                        List.of(NUMBER, WORD)),
                 Arguments.of("Float hex numbers",
                         "0Xf7p6",
                         List.of(HEX_NUMBER, WORD))