diff --git a/build/Build.go b/build/Build.go
index c9c6943..368b711 100644
--- a/build/Build.go
+++ b/build/Build.go
@@ -5,9 +5,12 @@ import (
 	"bytes"
 	"os"
 	"path/filepath"
+	"strings"
 
-	"git.akyoto.dev/cli/q/build/elf"
-	"git.akyoto.dev/cli/q/cli/log"
+	"git.akyoto.dev/cli/q/directory"
+	"git.akyoto.dev/cli/q/elf"
+	"git.akyoto.dev/cli/q/errors"
+	"git.akyoto.dev/cli/q/log"
 )
 
 // Build describes a compiler build.
@@ -43,29 +46,25 @@ func (build *Build) Run() error {
 	return nil
 }
 
-// Executable returns the path to the executable.
-func (build *Build) Executable() string {
-	return filepath.Join(build.Directory, build.Name)
-}
-
 // Compile compiles all the functions.
 func (build *Build) Compile() error {
-	file, err := os.Open(build.Directory)
+	stat, err := os.Stat(build.Directory)
 
 	if err != nil {
 		return err
 	}
 
-	defer file.Close()
-	files, err := file.Readdirnames(0)
-
-	if err != nil {
-		return err
+	if !stat.IsDir() {
+		return &errors.InvalidDirectory{Path: build.Directory}
 	}
 
-	for _, name := range files {
-		log.Info.Println(name)
-	}
+	directory.Walk(build.Directory, func(file string) {
+		if !strings.HasSuffix(file, ".q") {
+			return
+		}
+
+		log.Info.Println(file)
+	})
 
 	build.Code.Write([]byte{
 		0xb8, 0x01, 0x00, 0x00, 0x00, // mov eax, 1
@@ -83,6 +82,11 @@ func (build *Build) Compile() error {
 	return nil
 }
 
+// Executable returns the path to the executable.
+func (build *Build) Executable() string {
+	return filepath.Join(build.Directory, build.Name)
+}
+
 // writeToDisk writes the executable file to disk.
 func writeToDisk(filePath string, code []byte, data []byte) error {
 	file, err := os.Create(filePath)
diff --git a/cli/Build.go b/cli/Build.go
index b579dbf..7c8eac5 100644
--- a/cli/Build.go
+++ b/cli/Build.go
@@ -2,7 +2,7 @@ package cli
 
 import (
 	"git.akyoto.dev/cli/q/build"
-	"git.akyoto.dev/cli/q/cli/log"
+	"git.akyoto.dev/cli/q/log"
 )
 
 // Build builds an executable.
diff --git a/cli/Help.go b/cli/Help.go
index 61ba523..e34dc6c 100644
--- a/cli/Help.go
+++ b/cli/Help.go
@@ -1,7 +1,7 @@
 package cli
 
 import (
-	"git.akyoto.dev/cli/q/cli/log"
+	"git.akyoto.dev/cli/q/log"
 )
 
 // Help shows the command line argument usage.
diff --git a/cli/System.go b/cli/System.go
index 1b847aa..36fde71 100644
--- a/cli/System.go
+++ b/cli/System.go
@@ -4,7 +4,7 @@ import (
 	"os"
 	"runtime"
 
-	"git.akyoto.dev/cli/q/cli/log"
+	"git.akyoto.dev/cli/q/log"
 )
 
 // System shows system information.
diff --git a/cli/cli_test.go b/cli/cli_test.go
index c1e5861..111df5d 100644
--- a/cli/cli_test.go
+++ b/cli/cli_test.go
@@ -6,7 +6,7 @@ import (
 	"testing"
 
 	"git.akyoto.dev/cli/q/cli"
-	"git.akyoto.dev/cli/q/cli/log"
+	"git.akyoto.dev/cli/q/log"
 	"git.akyoto.dev/go/assert"
 )
 
diff --git a/directory/Walk.go b/directory/Walk.go
new file mode 100644
index 0000000..5595e3e
--- /dev/null
+++ b/directory/Walk.go
@@ -0,0 +1,61 @@
+package directory
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+const blockSize = 8 << 10
+
+// Walk calls your callback function for every file name inside the directory.
+// It doesn't distinguish between files and directories.
+func Walk(directory string, callBack func(string)) {
+	fd, err := syscall.Open(directory, 0, 0)
+
+	if err != nil {
+		panic(err)
+	}
+
+	defer syscall.Close(fd)
+	buffer := make([]byte, blockSize)
+
+	for {
+		n, err := syscall.ReadDirent(fd, buffer)
+
+		if err != nil {
+			panic(err)
+		}
+
+		if n <= 0 {
+			break
+		}
+
+		readBuffer := buffer[:n]
+
+		for len(readBuffer) > 0 {
+			dirent := (*syscall.Dirent)(unsafe.Pointer(&readBuffer[0]))
+			readBuffer = readBuffer[dirent.Reclen:]
+
+			// Skip deleted files
+			if dirent.Ino == 0 {
+				continue
+			}
+
+			// Skip hidden files
+			if dirent.Name[0] == '.' {
+				continue
+			}
+
+			for i, c := range dirent.Name {
+				if c != 0 {
+					continue
+				}
+
+				bytePointer := (*byte)(unsafe.Pointer(&dirent.Name[0]))
+				name := unsafe.String(bytePointer, i)
+				callBack(name)
+				break
+			}
+		}
+	}
+}
diff --git a/build/elf/ELF64.go b/elf/ELF64.go
similarity index 100%
rename from build/elf/ELF64.go
rename to elf/ELF64.go
diff --git a/build/elf/Header.go b/elf/Header.go
similarity index 100%
rename from build/elf/Header.go
rename to elf/Header.go
diff --git a/build/elf/ProgramHeader.go b/elf/ProgramHeader.go
similarity index 100%
rename from build/elf/ProgramHeader.go
rename to elf/ProgramHeader.go
diff --git a/build/elf/SectionHeader.go b/elf/SectionHeader.go
similarity index 100%
rename from build/elf/SectionHeader.go
rename to elf/SectionHeader.go
diff --git a/build/elf/elf.md b/elf/elf.md
similarity index 100%
rename from build/elf/elf.md
rename to elf/elf.md
diff --git a/errors/InvalidPath.go b/errors/InvalidPath.go
new file mode 100644
index 0000000..0b71fcf
--- /dev/null
+++ b/errors/InvalidPath.go
@@ -0,0 +1,15 @@
+package errors
+
+import "fmt"
+
+type InvalidDirectory struct {
+	Path string
+}
+
+func (err *InvalidDirectory) Error() string {
+	if err.Path == "" {
+		return "Invalid directory"
+	}
+
+	return fmt.Sprintf("Invalid directory '%s'", err.Path)
+}
diff --git a/cli/log/log.go b/log/log.go
similarity index 100%
rename from cli/log/log.go
rename to log/log.go