Add example with lua built-in function

.gitignore

@@ -1,2 +1,6 @@
 /01-LoadJsonFile
+/02-TestLuaScript
+/03-UseGoFuncInLua
+/doll
+/doll-master
 /*.exe

Makefile

@@ -13,9 +13,9 @@ WINDOWS_BINARY2=${MYNAME2}.exe
 RMCMD=rm -rf
 EXAMPLE01=01-LoadJsonFile
 EXAMPLE02=02-TestLuaScript
+EXAMPLE03=03-UseGoFuncInLua
 
-# На windows имя бинарника может зависеть не только от платформы, но и от выбранной цели, для linux-а суффикс .exe
+# On windows binary name can depend not only on platform selected, but target too, we need no .exe suffix for linux bin.
-# не нужен
 ifeq ($(OS),Windows_NT)
 ifdef GOOS
 ifeq ($(GOOS),windows)
@@ -34,7 +34,7 @@ RMCMD=DEL /Q /F
 endif
 endif
 
-# Явно определяем символ новой строки, чтобы избежать неоднозначности на windows
+# Set newline symbol explicitly to aboud undefined behaviour in windows.
 define IFS
 
 endef
@@ -77,6 +77,8 @@ ifeq ($(SHELL),sh.exe)
 	if exist ${EXAMPLE01} ${RMCMD} ${EXAMPLE01}
 	if exist ${EXAMPLE02}.exe ${RMCMD} ${EXAMPLE02}.exe
 	if exist ${EXAMPLE02} ${RMCMD} ${EXAMPLE02}
+		if exist ${EXAMPLE03}.exe ${RMCMD} ${EXAMPLE03}.exe
+	if exist ${EXAMPLE03} ${RMCMD} ${EXAMPLE03}
 else  # not ifeq ($(SHELL),sh.exe)
 	${RMCMD} ./${WINDOWS_BINARY1}
 	${RMCMD} ./${UNIX_BINARY1}
@@ -86,12 +88,15 @@ else  # not ifeq ($(SHELL),sh.exe)
 	${RMCMD} ./${EXAMPLE01}
 	${RMCMD} ./${EXAMPLE02}.exe
 	${RMCMD} ./${EXAMPLE02}
+	${RMCMD} ./${EXAMPLE03}.exe
+	${RMCMD} ./${EXAMPLE03}
 endif # ifeq ($(SHELL),sh.exe)
 else  # not ifeq ($(OS),Windows_NT)
 	${RMCMD} ./${UNIX_BINARY1}
 	${RMCMD} ./${UNIX_BINARY2}
 	${RMCMD} ${EXAMPLE01}
 	${RMCMD} ${EXAMPLE02}
+	${RMCMD} ${EXAMPLE03}
 endif
 
 
@@ -121,7 +126,7 @@ else  # not  ($(OS),Windows_NT)
 endif # ifeq ($(OS),Windows_NT)
 
 
-02-TestLuaScript: clean
+${EXAMPLE02}: clean
 ifeq ($(OS),Windows_NT)
 # Looks like on windows gnu make explicitly set SHELL to sh.exe, if it was not set.
 ifeq ($(SHELL), sh.exe)
@@ -141,4 +146,24 @@ else  # not  ($(OS),Windows_NT)
 endif # ifeq ($(OS),Windows_NT)
 
 
+${EXAMPLE03}: clean
+ifeq ($(OS),Windows_NT)
+# Looks like on windows gnu make explicitly set SHELL to sh.exe, if it was not set.
+ifeq ($(SHELL), sh.exe)
+#       # Vanilla cmd.exe / powershell.
+	SET "CGO_ENABLED=0"
+	go build ${BUILDOPTS} -o ${EXAMPLE03}.exe ./cmd/${EXAMPLE03}
+else ifeq (,$(findstring(Git/usr/bin/sh.exe, $(SHELL))))
+#       # git-bash
+	CGO_ENABLED=0 go build ${BUILDOPTS} -o ${EXAMPLE03}.exe ./cmd/${EXAMPLE03}
+else  # not ifeq (,$(findstring(Git/usr/bin/sh.exe, $(SHELL))))
+#       # Some other shell.
+#       # TODO: handle it.
+	$(info "-- Dunno how to handle this shell: ${SHELL}")
+endif # ifeq (,$(findstring(Git/usr/bin/sh.exe, $(SHELL))))
+else  # not  ($(OS),Windows_NT)
+	CGO_ENABLED=0 go build ${BUILDOPTS} -o ${EXAMPLE03} ./cmd/${EXAMPLE03}
+endif # ifeq ($(OS),Windows_NT)
+
+
 # vim: set ft=make noet ai ts=4 sw=4 sts=4:

example_data/03-test.lua

@@ -0,0 +1,3 @@
+print("4 * 4 = " .. square(4))
+
+-- vim: set ft=lua noet ai ts=4 sw=4 sts=4:

examples/03-UseGoFuncInLua/main.go

@@ -0,0 +1,59 @@
+package main
+
+// This exmple taken from https://otm.github.io/2015/07/embedding-lua-in-go/ .
+
+import (
+	"doll/internal/log"
+	"os"
+
+	lua "github.com/yuin/gopher-lua"
+)
+
+// square multiplies number by itself.
+func square(L *lua.LState) int {
+	// get first (1) function argument and convert to int
+	i := L.ToInt(1)
+
+	// make calculation and cast to LNumber
+	ln := lua.LNumber(i * i)
+
+	// Push it to the stack
+	L.Push(ln)
+
+	// Notify that we pushed one value to the stack
+	return 1
+}
+
+func main() {
+	// Init log subsystem.
+	log.Init("info", os.Stderr)
+
+	file := "example_data/03-test.lua"
+
+	// Load the Lua script file.
+	log.Infof("Loading %s", file)
+
+	// We can execute script directly via L.DoFile("./example_data/03-test.lua") but in practice we'll get scripts as
+	// strings - snippets from templates - so, testing/checking how it works is not use for project.
+	luaCode, err := os.ReadFile(file)
+
+	if err != nil {
+		log.Fatalf("Error reading Lua file %s: %s", file, err)
+	}
+
+	log.Info("Creating new Lua state")
+	L := lua.NewState()
+	defer L.Close()
+
+	log.Info("Registering go function as lua built-in function")
+	L.SetGlobal("square", L.NewFunction(square))
+
+	log.Info("Evaluating Lua code")
+	if err := L.DoString(string(luaCode)); err != nil {
+		log.Errorf("Error evaluating Lua code: %s", err)
+
+		os.Exit(1)
+	}
+}
+
+/* vim: set ft=go noet ai ts=4 sw=4 sts=4: */