1 files changed, 57 insertions, 0 deletions
diff --git a/lib/Lexer/Lexer.cc b/lib/Lexer/Lexer.cc
new file mode 100644
index 0000000..b04438b
--- /dev/null
+++ b/lib/Lexer/Lexer.cc
@@ -0,0 +1,57 @@
+#include "cps/Lexer.h"
+#include <cctype>
+#include <cstdio>
+
+using namespace cps;
+
+int Lexer::gettok() {
+    static int LastChar = ' ';
+
+    while (isspace(LastChar))
+        LastChar = getchar();
+
+    if (isalpha(LastChar)) {
+        IdentifierStr = LastChar;
+        while (isalnum((LastChar = getchar())) || LastChar == '_')
+            IdentifierStr += LastChar;
+
+        if (IdentifierStr == "DECLARE") return tok_declare;
+        if (IdentifierStr == "INTEGER") return tok_integer_kw;
+        if (IdentifierStr == "INPUT") return tok_input;
+        if (IdentifierStr == "OUTPUT") return tok_output;
+        return tok_identifier;
+    }
+
+    if (isdigit(LastChar)) {
+        std::string NumStr;
+        do {
+            NumStr += LastChar;
+            LastChar = getchar();
+        } while (isdigit(LastChar));
+        NumVal = strtol(NumStr.c_str(), nullptr, 10);
+        return tok_number;
+    }
+
+    if (LastChar == '<') {
+        LastChar = getchar();
+        if (LastChar == '-') {
+            LastChar = getchar();
+            return tok_assign;
+        }
+        return '<';
+    }
+
+    // for comments
+    
+    if (LastChar == ':') {
+        LastChar = getchar();
+        return tok_colon;
+    }
+
+    if (LastChar == EOF)
+        return tok_eof;
+
+    int ThisChar = LastChar;
+    LastChar = getchar();
+    return ThisChar;
+}