From 8a460f08053e5eafaf1b513154c30cc433064b05 Mon Sep 17 00:00:00 2001
From: Beforerr <zzj956959688@gmail.com>
Date: Sat, 16 Nov 2024 15:48:07 -0800
Subject: [PATCH] feat:  inner constructor for Particle

---
 docs/src/api.md   |  1 -
 docs/src/index.md |  8 ++++----
 src/types.jl      | 11 +++++++++--
 test/types.jl     |  9 +++++++++
 4 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/docs/src/api.md b/docs/src/api.md
index 2e869e5..d0b89f1 100644
--- a/docs/src/api.md
+++ b/docs/src/api.md
@@ -11,7 +11,6 @@ Order = [:type]
 ## Constructors
 
 ```@docs
-Particle
 proton
 electron
 ```
diff --git a/docs/src/index.md b/docs/src/index.md
index 92a33c7..6c07440 100644
--- a/docs/src/index.md
+++ b/docs/src/index.md
@@ -35,15 +35,15 @@ p = proton()         # proton
 α = Particle("alpha") # alpha particle
 
 # Create ions and isotopes
-fe3 = Particle("Fe3+")     # Iron(III) ion
-fe56 = Particle("Fe-56")   # Iron-56
+fe = Particle("Fe-56 3+")     # Iron(III) ion
+fe54 = Particle(:Fe, 3, 54)
 d = Particle("D+")         # Deuteron
 
 # Access properties
 println("Electron mass: ", mass(e))
 println("Alpha particle charge: ", charge(α))
-println("Iron charge: ", charge(fe3))
-println("Iron-56 mass number: ", mass_number(fe56))
+println("Iron(III) ion charge: ", charge(fe))
+println("Iron-54 mass number: ", mass_number(fe54))
 println("Deuteron mass: ", mass(d))
 ```
 
diff --git a/src/types.jl b/src/types.jl
index a326ff9..0358dea 100644
--- a/src/types.jl
+++ b/src/types.jl
@@ -18,7 +18,7 @@ Implementation type for charged particles.
 # Fields
 - `symbol::Symbol`: Chemical symbol or particle identifier (e.g., :Fe, :e, :μ)
 - `charge_number::Int`: Number of elementary charges (can be negative)
-- `mass_number::Int`: Total number of nucleons (protons + neutrons)
+- `mass_number::Int`: Total number of nucleons (protons + neutrons). If not provided, defaults to the most common isotope mass number
 
 # Notes
 - Mass number : For elementary particles like electrons and muons, `mass_number` is 0
@@ -35,7 +35,14 @@ struct Particle <: AbstractParticle
     symbol::Symbol
     charge_number::Int
     mass_number::Int
-
+    function Particle(symbol, charge_number, mass_number=nothing)
+        if isnothing(mass_number)
+            mass_number = elements[symbol].mass_number
+        else
+            mass_number >= 0 || throw(ArgumentError("Mass number must be non-negative, got $mass_number"))
+        end
+        new(symbol, charge_number, mass_number)
+    end
 end
 
 """
diff --git a/test/types.jl b/test/types.jl
index 665257e..d610e73 100644
--- a/test/types.jl
+++ b/test/types.jl
@@ -1,6 +1,15 @@
 using Test, ChargedParticles, Unitful
+using ChargedParticles: is_electron, is_proton
 using Unitful: q
 
+@testset "Constructor" begin
+    # Test invalid mass numbers
+    @test_throws ArgumentError Particle(:He, 2, -1)
+
+    # Default mass number
+    @test mass_number(Particle(:He, 2)) == 4
+end
+
 @testset "String Constructor" begin
     # Test common aliases
     @test is_electron(Particle("electron"))