From ee390003371bee6174850434ff34f1b78b279cf1 Mon Sep 17 00:00:00 2001
From: Didictateur <adrien.decosse@gmail.com>
Date: Tue, 17 Feb 2026 19:46:17 +0100
Subject: [PATCH] can compute external forces

---
 examples/pendule_simple.py |  4 +++-
 legrandchien.py            | 24 ++++++++++++++++++++++--
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/examples/pendule_simple.py b/examples/pendule_simple.py
index a669249..65e0d16 100644
--- a/examples/pendule_simple.py
+++ b/examples/pendule_simple.py
@@ -10,6 +10,7 @@ import numpy as np
 g = lgc.Const(-10)
 m = lgc.Const(1)
 r = lgc.Const(1)
+c = lgc.Const(0.3)
 
 theta = lgc.Var()
 
@@ -20,13 +21,14 @@ T = 0.5 * m * (x.diff()**2 + y.diff()**2)
 V = m * g * r * lgc.cos(theta)
 
 L = T - V
+F = 0.5 * c * (x.diff()**2 + y.diff()**2)
 
 init = {
     theta : [-3 * 3.14/4, 0], # theta, theta.diff()
 }
 
 dt = 0.01
-data = L.solve(init, 10, dt, True)
+data = L.solve(init, 10, dt, True, F)
 
 # Extraire les positions
 times = sorted(data.keys())
diff --git a/legrandchien.py b/legrandchien.py
index 9992a05..5d02f3a 100644
--- a/legrandchien.py
+++ b/legrandchien.py
@@ -33,6 +33,22 @@ class Const:
     def simplify(self):
         pass
 
+    def diff(self):
+        return Equation(
+            Operation.CONST,
+            None,
+            None,
+            Const(0)
+        )
+    
+    def partial(self, _):
+        return Equation(
+            Operation.CONST,
+            None,
+            None,
+            Const(0)
+        )
+
     def __str__(self):
         return str(self.value)
 
@@ -529,7 +545,7 @@ class Equation:
             self.compile()
         return self.compiled_function(dico)
         
-    def solve(self, init, tmax=10, dt=0.01, progress_bar=True):
+    def solve(self, init, tmax=10, dt=0.01, progress_bar=True, F_ext = Const(0)):
         dico = {}
         for v_name, v_init in init.items():
             for i in range(len(v_init)):
@@ -541,7 +557,11 @@ class Equation:
         equations = []
         # print([v.name for v in variables])
         for var in variables:
-            equations.append(self.partial(var.diff().name).diff() - self.partial(var.name))
+            equations.append(
+                self.partial(var.diff().name).diff()\
+                - self.partial(var.name)\
+                + F_ext.partial(var.diff().name)
+            )
 
         unknown = self.getUnknown(dico)
         for eq in equations: