builtins: add doto macro

2 files changed, 53 insertions, 0 deletions

diff --git a/alv/builtins.moon b/alv/builtins.moon
index 7640ac8..84978f1 100644
--- a/alv/builtins.moon
+++ b/alv/builtins.moon
@@ -753,6 +753,37 @@ is always inserted as the last argument."
 
   value: mk_thread '->>', false
 
+doto = Constant.meta
+  meta:
+    name: 'doto'
+    summary: "Pass argument to multiple functions."
+    examples: { '(doto initial [expr1 expr2…])' }
+    description: "
+Insert the result of the `initial` expression to all other expressions `expr1`, `expr2`, …
+The value is always inserted as the first argument.
+
+Returns the result of the `initial` expression."
+
+  value: class extends Builtin
+    eval: (scope, tail) =>
+      L\trace "evaling #{@}"
+      assert #tail > 1, "'#{name}' requires at least 2 arguments"
+
+      value = L\push tail[1]\eval, scope
+
+      children = for cell in *tail[2,]
+        assert cell.__class == Cell, "'#{name}'s arguments have to be expressions"
+
+        args = [c for c in *cell.children]
+        table.insert args, 2, Dummy value\make_ref!
+
+        cell = Cell cell.tag, args
+        cell\eval scope
+
+      table.insert children, value
+
+      super RTNode :children, result: value.result
+
 Constant.meta
   meta:
     summary: "builtin operators and constants."
@@ -782,6 +813,7 @@ Constant.meta
 
     '->': thread_first
     '->>': thread_last
+    :doto
 
     :mkarray, :mkstruct
     :fmt
diff --git a/examples/glsl-view/stream-controls.alv b/examples/glsl-view/stream-controls.alv
new file mode 100644
index 0000000..fb37c31
--- /dev/null
+++ b/examples/glsl-view/stream-controls.alv
@@ -0,0 +1,21 @@
+([1]import* glsl-view link-time)
+([2]import osc)
+
+([3]def 
+  *clock* ([8]clock false 120)
+  *oscout* ([5]osc/connect 'localhost' 9000))
+
+([6]def 
+  paused? ([12]switch ([13]every 2) true false)
+  cam ([16]doto ([7]stream-source 'webcam' '2D' '/dev/video0')
+    ([11]freeze paused?)
+    ([14]step! ([15]every 0.5))))
+
+([9]draw $[10]shader"
+in vec2 uv;
+out vec4 color;
+
+void main() {
+  color = texture($cam , uv);
+  color.rgb = mix(color.rgb, color.rrr, $paused? ? 1 : 0);
+}")