gen: fix multiple call of expression in match (#6324)

examples/sokol/particles/particles.v

@@ -0,0 +1,139 @@
+// Copyright(C) 2019 Lars Pontoppidan. All rights reserved.
+// Use of this source code is governed by an MIT license file distributed with this software package
+module main
+
+import time
+import sokol
+import sokol.sapp
+import sokol.gfx
+import sokol.sgl
+import particle
+
+const (
+	used_import = sokol.used_import
+)
+
+fn main() {
+	mut app := &App{
+		width: 800
+		height: 400
+		pass_action: gfx.create_clear_pass(0.1, 0.1, 0.1, 1.0)
+	}
+	app.init()
+	app.run()
+}
+
+struct App {
+	pass_action C.sg_pass_action
+mut:
+	width       int
+	height      int
+	frame       i64
+	last        i64
+	ps          particle.System
+}
+
+fn (mut a App) init() {
+	a.frame = 0
+	a.last = time.ticks()
+	a.ps = particle.System{
+		width: a.width
+		height: a.height
+	}
+	a.ps.init(particle.SystemConfig{
+		pool: 20000
+	})
+}
+
+fn (mut a App) cleanup() {
+	a.ps.free()
+}
+
+fn (mut a App) run() {
+	title := 'V Particle Example'
+	desc := C.sapp_desc{
+		width: a.width
+		height: a.height
+		user_data: a
+		init_userdata_cb: init
+		frame_userdata_cb: frame
+		event_userdata_cb: event
+		window_title: title.str
+		html5_canvas_name: title.str
+		cleanup_userdata_cb: cleanup
+	}
+	sapp.run(&desc)
+}
+
+fn (a App) draw() {
+	a.ps.draw()
+}
+
+fn init(user_data voidptr) {
+	desc := sapp.create_desc()
+	gfx.setup(&desc)
+	sgl_desc := C.sgl_desc_t{
+		max_vertices: 50 * 65536
+	}
+	sgl.setup(&sgl_desc)
+}
+
+fn cleanup(user_data voidptr) {
+	mut app := &App(user_data)
+	app.cleanup()
+	gfx.shutdown()
+}
+
+fn frame(user_data voidptr) {
+	mut app := &App(user_data)
+	app.width = sapp.width()
+	app.height = sapp.height()
+	t := time.ticks()
+	dt := f64(t - app.last) / 1000.0
+	app.ps.update(dt)
+	draw(app)
+	gfx.begin_default_pass(&app.pass_action, app.width, app.height)
+	sgl.draw()
+	gfx.end_pass()
+	gfx.commit()
+	app.frame++
+	app.last = t
+}
+
+fn event(ev &C.sapp_event, user_data voidptr) {
+	mut app := &App(user_data)
+	if ev.@type == .mouse_move {
+		app.ps.explode(ev.mouse_x, ev.mouse_y)
+	}
+	if ev.@type == .mouse_up || ev.@type == .mouse_down {
+		if ev.mouse_button == .left {
+			is_pressed := ev.@type == .mouse_down
+			if is_pressed {
+				app.ps.explode(ev.mouse_x, ev.mouse_y)
+			}
+		}
+	}
+	if ev.@type == .key_up || ev.@type == .key_down {
+		if ev.key_code == .r {
+			is_pressed := ev.@type == .key_down
+			if is_pressed {
+				app.ps.reset()
+			}
+		}
+	}
+	if ev.@type == .touches_began || ev.@type == .touches_moved {
+		if ev.num_touches > 0 {
+			touch_point := ev.touches[0]
+			app.ps.explode(touch_point.pos_x, touch_point.pos_y)
+		}
+	}
+}
+
+fn draw(a &App) {
+	sgl.defaults()
+	sgl.matrix_mode_projection()
+	sgl.ortho(0, f32(sapp.width()), f32(sapp.height()), 0.0, -1.0, 1.0)
+	sgl.push_matrix()
+	a.draw()
+	sgl.pop_matrix()
+}