examples: move the particle module in modules/particle

The goal is enabling running `v build-examples` from outside vroot.
The modules/ folders are already skipped when building examples.

examples/sokol/particles/modules/particle/LICENSE

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+MIT License
+
+Copyright (c) 2019 Lars Pontoppidan
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

examples/sokol/particles/modules/particle/color.v

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+// 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 particle
+
+// * Color
+pub struct Color {
+mut:
+	r byte
+	g byte
+	b byte
+	a byte
+}

examples/sokol/particles/modules/particle/particle.v

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+// 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 particle
+
+import vec2
+import sokol.sgl
+
+const (
+	default_life_time = 1000
+	default_v_color   = Color{93, 136, 193, 255}
+)
+
+// * Module public
+pub fn new(location vec2.Vec2) &Particle {
+	p := &Particle{
+		location: location
+		velocity: vec2.Vec2{0, 0}
+		acceleration: vec2.Vec2{0, 0}
+		color: default_v_color
+		life_time: default_life_time
+		life_time_init: default_life_time
+	}
+	return p
+}
+
+fn remap(v, min, max, new_min, new_max f64) f64 {
+	return (((v - min) * (new_max - new_min)) / (max - min)) + new_min
+}
+
+// * Particle
+pub struct Particle {
+mut:
+	location       vec2.Vec2
+	velocity       vec2.Vec2
+	acceleration   vec2.Vec2
+	color          Color
+	life_time      f64
+	life_time_init f64
+}
+
+pub fn (mut p Particle) update(dt f64) {
+	mut acc := p.acceleration
+	acc.multiply_f64(dt)
+	p.velocity = p.velocity.add(acc)
+	p.location = p.location.add(p.velocity)
+	lt := p.life_time - (1000 * dt)
+	if lt > 0 {
+		p.life_time = lt
+		p.color.r = p.color.r - 1 // byte(remap(p.life_time,0.0,p.life_time_init,0,p.color.r))
+		p.color.g = p.color.g - 1 // byte(remap(p.life_time,0.0,p.life_time_init,0,p.color.g))
+		p.color.b = p.color.b - 1 // byte(remap(p.life_time,0.0,p.life_time_init,0,p.color.b))
+		// p.color.a = byte(remap(p.life_time,0.0,p.life_time_init,0,255))
+	} else {
+		p.life_time = 0
+	}
+}
+
+pub fn (p Particle) is_dead() bool {
+	return p.life_time <= 0.0
+}
+
+pub fn (p Particle) draw() {
+	l := p.location
+	sgl.c4b(p.color.r, p.color.g, p.color.b, p.color.a)
+	lx := f32(l.x)
+	ly := f32(l.y)
+	sgl.v2f(lx, ly)
+	sgl.v2f(lx + 2, ly)
+	sgl.v2f(lx + 2, ly + 2)
+	sgl.v2f(lx, ly + 2)
+}
+
+pub fn (mut p Particle) reset() {
+	p.location.zero()
+	p.acceleration.zero()
+	p.velocity.zero()
+	// p.color = Color{93, 136, 193, 255}
+	p.color = default_v_color
+	p.life_time = default_life_time
+	p.life_time_init = p.life_time
+}

examples/sokol/particles/modules/particle/system.v

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+// 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 particle
+
+import vec2
+import rand
+import sokol.sgl
+
+pub struct SystemConfig {
+	pool int
+}
+
+pub struct System {
+	width  int
+	height int
+mut:
+	pool   []&Particle
+	bin    []&Particle
+}
+
+pub fn (mut s System) init(sc SystemConfig) {
+	for i := 0; i < sc.pool; i++ {
+		p := new(vec2.Vec2{f32(s.width) * 0.5, f32(s.height) * 0.5})
+		s.pool << p
+	}
+}
+
+pub fn (mut s System) update(dt f64) {
+	mut p := &Particle(0)
+	for i := 0; i < s.pool.len; i++ {
+		p = s.pool[i]
+		p.update(dt)
+		if p.is_dead() {
+			s.bin << p
+			s.pool.delete(i)
+		}
+	}
+}
+
+pub fn (s System) draw() {
+	sgl.begin_quads()
+	for p in s.pool {
+		p.draw()
+	}
+	sgl.end()
+}
+
+pub fn (mut s System) reset() {
+	for i in 0..s.pool.len {
+		mut p := s.pool[i]
+		p.reset()
+		p.life_time = 0
+	}
+	for i in 0..s.bin.len {
+		mut p := s.pool[i]
+		p.reset()
+		p.life_time = 0
+	}
+}
+
+pub fn (mut s System) explode(x, y f32) {
+	mut reserve := 500
+	center := vec2.Vec2{x, y}
+	mut p := &Particle(0)
+	for i := 0; i < s.bin.len && reserve > 0; i++ {
+		p = s.bin[i]
+		p.reset()
+		p.location.from(center)
+		p.acceleration = vec2.Vec2{rand.f32_in_range(-0.5, 0.5), rand.f32_in_range(-0.5,
+			0.5)}
+		p.velocity = vec2.Vec2{rand.f32_in_range(-0.5, 0.5), rand.f32_in_range(-0.5, 0.5)}
+		p.life_time = rand.f64_in_range(500, 2000)
+		s.pool << p
+		s.bin.delete(i)
+		reserve--
+	}
+}
+
+pub fn (mut s System) free() {
+	for p in s.pool {
+		if p == 0 {
+			print(ptr_str(p) + ' ouch')
+			continue
+		}
+		unsafe {
+			free(p)
+		}
+	}
+	s.pool.clear()
+	for p in s.bin {
+		if p == 0 {
+			print(ptr_str(p) + ' ouch')
+			continue
+		}
+		unsafe {
+			// println('Freeing from bin')
+			free(p)
+		}
+	}
+	s.bin.clear()
+}

examples/sokol/particles/modules/particle/vec2/vec2.v

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+// 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 vec2
+
+pub struct Vec2 {
+pub mut:
+	x f64
+	y f64
+}
+
+pub fn (mut v Vec2) zero() {
+	v.x = 0.0
+	v.y = 0.0
+}
+
+pub fn (mut v Vec2) from(src Vec2) {
+	v.x = src.x
+	v.y = src.y
+}
+
+// * Addition
+// + operator overload. Adds two vectors
+pub fn (v1 Vec2) +(v2 Vec2) Vec2 {
+	return Vec2{v1.x + v2.x, v1.y + v2.y}
+}
+
+pub fn (v Vec2) add(vector Vec2) Vec2 {
+	return Vec2{v.x + vector.x, v.y + vector.y}
+}
+
+pub fn (v Vec2) add_f64(scalar f64) Vec2 {
+	return Vec2{v.x + scalar, v.y + scalar}
+}
+
+pub fn (mut v Vec2) plus(vector Vec2) {
+	v.x += vector.x
+	v.y += vector.y
+}
+
+pub fn (mut v Vec2) plus_f64(scalar f64) {
+	v.x += scalar
+	v.y += scalar
+}
+
+// * Subtraction
+pub fn (v1 Vec2) -(v2 Vec2) Vec2 {
+	return Vec2{v1.x - v2.x, v1.y - v2.y}
+}
+
+pub fn (v Vec2) sub(vector Vec2) Vec2 {
+	return Vec2{v.x - vector.x, v.y - vector.y}
+}
+
+pub fn (v Vec2) sub_f64(scalar f64) Vec2 {
+	return Vec2{v.x - scalar, v.y - scalar}
+}
+
+pub fn (mut v Vec2) subtract(vector Vec2) {
+	v.x -= vector.x
+	v.y -= vector.y
+}
+
+pub fn (mut v Vec2) subtract_f64(scalar f64) {
+	v.x -= scalar
+	v.y -= scalar
+}
+
+// * Multiplication
+pub fn (v1 Vec2) *(v2 Vec2) Vec2 {
+	return Vec2{v1.x * v2.x, v1.y * v2.y}
+}
+
+pub fn (v Vec2) mul(vector Vec2) Vec2 {
+	return Vec2{v.x * vector.x, v.y * vector.y}
+}
+
+pub fn (v Vec2) mul_f64(scalar f64) Vec2 {
+	return Vec2{v.x * scalar, v.y * scalar}
+}
+
+pub fn (mut v Vec2) multiply(vector Vec2) {
+	v.x *= vector.x
+	v.y *= vector.y
+}
+
+pub fn (mut v Vec2) multiply_f64(scalar f64) {
+	v.x *= scalar
+	v.y *= scalar
+}