diff --git a/amend/lexer.l b/amend/lexer.l
new file mode 100644
index 0000000..80896d1
--- /dev/null
+++ b/amend/lexer.l
@@ -0,0 +1,299 @@
+/*
+ * Copyright (C) 2007 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+%{
+    #include <stdio.h>
+    #include <stdlib.h>
+    #include "ast.h"
+    #include "lexer.h"
+    #include "parser.h"
+
+    const char *tokenToString(int token)
+    {
+        static char scratch[128];
+
+        switch (token) {
+        case TOK_AND:
+            return "&&";
+        case TOK_OR:
+            return "||";
+        case TOK_EQ:
+            return "==";
+        case TOK_NE:
+            return "!=";
+        case TOK_GE:
+            return ">=";
+        case TOK_LE:
+            return "<=";
+        case TOK_EOF:
+            return "EOF";
+        case TOK_EOL:
+            return "EOL\n";
+        case TOK_STRING:
+            snprintf(scratch, sizeof(scratch),
+                    "STRING<%s>", yylval.literalString);
+            return scratch;
+        case TOK_IDENTIFIER:
+            snprintf(scratch, sizeof(scratch), "IDENTIFIER<%s>",
+                    yylval.literalString);
+            return scratch;
+        case TOK_WORD:
+            snprintf(scratch, sizeof(scratch), "WORD<%s>",
+                    yylval.literalString);
+            return scratch;
+        default:
+            if (token > ' ' && token <= '~') {
+                scratch[0] = (char)token;
+                scratch[1] = '\0';
+            } else {
+                snprintf(scratch, sizeof(scratch), "??? <%d>", token);
+            }
+            return scratch;
+        }
+    }
+
+    typedef struct {
+        char *value;
+        char *nextc;
+        unsigned int alloc_size;
+    } AmString;
+
+    static int addCharToString(AmString *str, char c)
+    {
+        if ((unsigned int)(str->nextc - str->value) >= str->alloc_size) {
+            char *new_value;
+            unsigned int new_size;
+
+            new_size = (str->alloc_size + 1) * 2;
+            if (new_size < 64) {
+                new_size = 64;
+            }
+
+            new_value = (char *)realloc(str->value, new_size);
+            if (new_value == NULL) {
+                yyerror("out of memory");
+                return -1;
+            }
+            str->nextc = str->nextc - str->value + new_value;
+            str->value = new_value;
+            str->alloc_size = new_size;
+        }
+        *str->nextc++ = c;
+        return 0;
+    }
+
+    static int setString(AmString *str, const char *p)
+    {
+        str->nextc = str->value;
+        while (*p != '\0') {
+//TODO: add the whole string at once
+            addCharToString(str, *p++);
+        }
+        return addCharToString(str, '\0');
+    }
+
+    static AmString gStr = { NULL, NULL, 0 };
+    static int gLineNumber = 1;
+    static AmArgumentType gArgumentType = AM_UNKNOWN_ARGS;
+    static const char *gErrorMessage = NULL;
+
+#if AMEND_LEXER_BUFFER_INPUT
+    static const char *gInputBuffer;
+    static const char *gInputBufferNext;
+    static const char *gInputBufferEnd;
+
+# define YY_INPUT(buf, result, max_size) \
+    do { \
+        int nbytes = gInputBufferEnd - gInputBufferNext; \
+        if (nbytes > 0) { \
+            if (nbytes > max_size) { \
+                nbytes = max_size; \
+            } \
+            memcpy(buf, gInputBufferNext, nbytes); \
+            gInputBufferNext += nbytes; \
+            result = nbytes; \
+        } else { \
+            result = YY_NULL; \
+        } \
+    } while (false)
+#endif  // AMEND_LEXER_BUFFER_INPUT
+
+%}
+
+%option noyywrap
+
+%x QUOTED_STRING BOOLEAN WORDS
+
+ident [a-zA-Z_][a-zA-Z_0-9]*
+word [^ \t\r\n"]+
+
+%%
+    /* This happens at the beginning of each call to yylex().
+     */
+    if (gArgumentType == AM_WORD_ARGS) {
+        BEGIN(WORDS);
+    } else if (gArgumentType == AM_BOOLEAN_ARGS) {
+        BEGIN(BOOLEAN);
+    }
+
+        /*xxx require everything to be 7-bit-clean, printable characters */
+<INITIAL>{
+        {ident}/[ \t\r\n] {
+                /* The only token we recognize in the initial
+                 * state is an identifier followed by whitespace.
+                 */
+                setString(&gStr, yytext);
+                yylval.literalString = gStr.value;
+                return TOK_IDENTIFIER;
+            }
+    }
+
+<BOOLEAN>{
+        {ident} {
+                /* Non-quoted identifier-style string */
+                setString(&gStr, yytext);
+                yylval.literalString = gStr.value;
+                return TOK_IDENTIFIER;
+            }
+        "&&"    return TOK_AND;
+        "||"    return TOK_OR;
+        "=="    return TOK_EQ;
+        "!="    return TOK_NE;
+        ">="    return TOK_GE;
+        "<="    return TOK_LE;
+        [<>()!,] return yytext[0];
+    }
+
+    /* Double-quoted string handling */
+
+<WORDS,BOOLEAN>\"  {
+        /* Initial quote */
+        gStr.nextc = gStr.value;
+        BEGIN(QUOTED_STRING);
+    }
+
+<QUOTED_STRING>{
+        \"  {
+                /* Closing quote */
+                BEGIN(INITIAL);
+                addCharToString(&gStr, '\0');
+                yylval.literalString = gStr.value;
+                if (gArgumentType == AM_WORD_ARGS) {
+                    return TOK_WORD;
+                } else {
+                    return TOK_STRING;
+                }
+            }
+
+        <<EOF>> |
+        \n  {
+                /* Unterminated string */
+                yyerror("unterminated string");
+                return TOK_ERROR;
+            }
+
+        \\\" {
+                /* Escaped quote */
+                addCharToString(&gStr, '"');
+            }
+
+        \\\\ {
+                /* Escaped backslash */
+                addCharToString(&gStr, '\\');
+            }
+
+        \\. {
+                /* No other escapes allowed. */
+                gErrorMessage = "illegal escape";
+                return TOK_ERROR;
+            }
+
+        [^\\\n\"]+ {
+                /* String contents */
+                char *p = yytext;
+                while (*p != '\0') {
+        /* TODO: add the whole string at once */
+                    addCharToString(&gStr, *p++);
+                }
+            }
+    }
+
+<WORDS>{
+        /*xxx look out for backslashes; escape backslashes and quotes */
+        /*xxx if a quote is right against a char, we should append */
+        {word} {
+                /* Whitespace-separated word */
+                setString(&gStr, yytext);
+                yylval.literalString = gStr.value;
+                return TOK_WORD;
+            }
+    }
+
+<INITIAL,WORDS,BOOLEAN>{
+        \n  {
+                /* Count lines */
+                gLineNumber++;
+                gArgumentType = AM_UNKNOWN_ARGS;
+                BEGIN(INITIAL);
+                return TOK_EOL;
+            }
+
+        /*xxx backslashes to extend lines? */
+            /* Skip whitespace and comments.
+             */
+        [ \t\r]+ ;
+        #.*      ;
+
+        .   {
+                /* Fail on anything we didn't expect. */
+                gErrorMessage = "unexpected character";
+                return TOK_ERROR;
+            }
+    }
+%%
+
+void
+yyerror(const char *msg)
+{
+    if (!strcmp(msg, "syntax error") && gErrorMessage != NULL) {
+        msg = gErrorMessage;
+        gErrorMessage = NULL;
+    }
+    fprintf(stderr, "line %d: %s at '%s'\n", gLineNumber, msg, yytext);
+}
+
+#if AMEND_LEXER_BUFFER_INPUT
+void
+setLexerInputBuffer(const char *buf, size_t buflen)
+{
+    gLineNumber = 1;
+    gInputBuffer = buf;
+    gInputBufferNext = gInputBuffer;
+    gInputBufferEnd = gInputBuffer + buflen;
+}
+#endif  // AMEND_LEXER_BUFFER_INPUT
+
+void
+setLexerArgumentType(AmArgumentType type)
+{
+    gArgumentType = type;
+}
+
+int
+getLexerLineNumber(void)
+{
+    return gLineNumber;
+}