added ccall model

Author: PTWaade

main.jl

@@ -76,6 +76,7 @@ end
 # although it's hardly a big deal.
 @include_model "Base Julia features" "control_flow"
 @include_model "Base Julia features" "multithreaded"
+@include_model "Base Julia features" "call_C"
 @include_model "Core Turing syntax" "broadcast_macro"
 @include_model "Core Turing syntax" "dot_assume"
 @include_model "Core Turing syntax" "dot_observe"

models/call_C.jl

@@ -0,0 +1,15 @@
+# Get name of C standard library depending on the platform
+libc_name = Sys.iswindows() ? "msvcrt.dll" :
+            Sys.isapple()   ? "libc.dylib" :
+                              "libc.so.6"
+
+@model function call_C(y)
+    x ~ Normal(0, 1)
+
+    # Call C library abs function
+    x_abs = @ccall libc_name.fabs(x::Cdouble)::Cdouble
+
+    y ~ Normal(0, x_abs)
+end
+
+model = call_C()