fix particle beam for N=1

Author: Datseris

src/billiards/particles.jl

@@ -150,9 +150,15 @@ The particle element type is `T`.
 """
 function particlebeam(x0, y0, φ, N, dx, ω = nothing, T = eltype(x0))
     n = cossin(φ)
-    xyφs = [
-    T.((x0 - i*dx*n[2]/N, y0 + i*dx*n[1]/N, φ)) for i in range(-N/2, N/2; length = N)
-    ]
+    if N > 1
+        xyφs = [
+        T.((x0 - i*dx*n[2]/N, y0 + i*dx*n[1]/N, φ)) for i in range(-N/2, N/2; length = N)
+        ]
+    elseif N == 1
+        xyφs = [T.((x0, y0, φ))]
+    else
+        error("must be N ≥ 1")
+    end
     if isnothing(ω)
         ps = [Particle(z...) for z in xyφs]
     else

src/billiards/standard_billiards.jl

@@ -245,6 +245,8 @@ function billiard_mushroom(stem_length = 1.0, stem_width=0.2, cap_radious=1.0,
 
     abs(sloc) + sw/2 > cr && error("Stem is outside the mushroom cap!")
 
+    sl, sw, cr, sloc = promote(sl, sw, cr, sloc)
+    T = eltype(sl)
     leftcorn = SV(-sw/2 + sloc, 0)
     rightcorn = SV(sw/2 + sloc, 0)
     upleftcorn = SV(-sw/2 + sloc, sl)
@@ -263,8 +265,7 @@ function billiard_mushroom(stem_length = 1.0, stem_width=0.2, cap_radious=1.0,
     capbotright = FiniteWall(
     uprightcorn, farright, SV(0, sw), false, "Cap bottom right")
 
-    cap = Semicircle([0.0, sl], cr, [0.0, -1.0], "Mushroom cap")
-
+    cap = Semicircle([0, sl], cr, [0, -T(1.0)], "Mushroom cap")
     return Billiard(stembot, stemright, capbotright, cap, capbotleft, stemleft)
 end