if args None don't add to constraints

gpkitmodels/GP/aircraft/wing/gustloading.py

@@ -16,7 +16,7 @@ class GustL(SparLoading):
 
     def setup(self, static, Wcent=None, Wwing=None, V=None, CL=None):
 
-        self.load = SparLoading.setup(self, static, Wcent)
+        self.load = SparLoading.setup(self, static, Wcent=Wcent)
         vgust = Variable("V_{gust}", 10, "m/s", "gust velocity")
         Ww = Variable("W_w", "lbf", "wing weight")
         v = Variable("V", "m/s", "speed")
@@ -35,12 +35,14 @@ def setup(self, static, Wcent=None, Wwing=None, V=None, CL=None):
 
         constraints = [
             # fit for arctan from 0 to 1, RMS = 0.044
-            V == v,
-            CL == cl,
-            Ww == Wwing,
             FitCS(df, agust, [cosminus1*vgust/v]),
             self.beam["\\bar{q}"] >= self.static["\\bar{c}"]*(
-                1 + 2*pi*agust/cl*(1+Ww/Wcent)),
+                1 + 2*pi*agust/cl*(1+Ww/self.W)),
             ]
 
+        if Wcent:
+            constraints.extend([V == v,
+                                CL == cl,
+                                Ww == Wwing])
+
         return self.load, constraints

gpkitmodels/GP/aircraft/wing/sparloading.py

@@ -30,7 +30,7 @@ def setup(self, static, Wcent=None):
         sigmacfrp = Variable("\\sigma_{CFRP}", 1700e6, "Pa", "CFRP max stress")
         taucfrp = Variable("\\tau_{CFRP}", 450e6, "Pa", "CFRP fabric stress")
         kappa = Variable("\\kappa", 0.2, "-", "max tip deflection ratio")
-        W = Variable("W", "lbf", "loading weight")
+        self.W = Variable("W", "lbf", "loading weight")
 
         with Vectorize(self.static.N-1):
             Mr = Variable("M_r", "N*m", "wing section root moment")
@@ -42,15 +42,17 @@ def setup(self, static, Wcent=None):
         constraints = [
             # dimensionalize moment of inertia and young's modulus
             self.beam["dx"] == self.static["d\\eta"],
-            W == Wcent,
             self.beam["\\bar{EI}"] <= (8*self.static["E"]*self.static["I"]/Nmax
-                                       / W/self.static["b"]**2),
-            Mr == (self.beam["\\bar{M}"][:-1]*W*Nmax*self.static["b"]/4),
+                                       / self.W/self.static["b"]**2),
+            Mr == (self.beam["\\bar{M}"][:-1]*self.W*Nmax*self.static["b"]/4),
             sigmacfrp >= Mr/self.static["S_y"],
             self.beam["\\bar{\\delta}"][-1] <= kappa,
-            taucfrp >= (self.beam["\\bar{S}"][-1]*W*Nmax/4
+            taucfrp >= (self.beam["\\bar{S}"][-1]*self.W*Nmax/4
                         / self.static["t_{shear}"]/self.static["c_{ave}"]
                         / self.static["\\tau"])
             ]
 
+        if Wcent:
+            constraints.extend([self.W == Wcent])
+
         return self.beam, constraints

gpkitmodels/GP/aircraft/wing/wing_test.py

@@ -23,10 +23,15 @@ def wing_test():
     W.substitutions[W.topvar("W")] = 50
     fs = FlightState()
     perf = W.flight_model(W, fs)
-    loading = W.loading(W, Wcent, W.topvar("W"), fs["V"], perf["C_L"])
-    loading = W.loading(W, Wcent)
-
-    m = Model(perf["C_d"], [W, fs, perf, loading])
+    loading = [W.spar.loading(W)]
+    loading[0].substitutions["W"] = 100
+    loading.append(W.spar.gustloading(W))
+    loading[1].substitutions["W"] = 100
+
+    m = Model(perf["C_d"], [loading[1]["V"] == fs["V"],
+                            loading[1]["c_l"] == perf["C_L"],
+                            loading[1]["W_w"] == W.topvar("W"),
+                            W, fs, perf, loading])
     m.solve("mosek")
 
 if __name__ == "__main__":