1 files changed, 128 insertions, 0 deletions
diff --git a/alv-lib/struct.moon b/alv-lib/struct.moon
new file mode 100644
index 0000000..b064e81
--- /dev/null
+++ b/alv-lib/struct.moon
@@ -0,0 +1,128 @@
+import Struct, Op, PureOp, Constant, Error, const, any from require 'alv.base'
+
+key_type = const.str / const.sym
+
+get = Constant.meta
+  meta:
+    name: 'get'
+    summary: "Index into a struct."
+    examples: { '(get struct key)' }
+    description: "Get the value at `key`.
+
+`key` has to be a constant expression."
+
+  value: class extends PureOp
+    pattern: any! + key_type
+    type: (inputs) =>
+      { struct, key } = inputs
+      struct\type!\get key.result!
+
+    tick: =>
+      { struct, key } = @unwrap_all!
+      @out\set struct[key]
+
+set = Constant.meta
+  meta:
+    name: 'set'
+    summary: "Update values in a struct."
+    examples: { '(set struct key val)' }
+    description: "Set the value for `key` to `val`.
+
+`key` has to be a constant expression. This is a pure op, so at most one of
+`struct` and `val` may be a !-stream."
+
+  value: class extends PureOp
+    pattern: any! + key_type + any!
+    type: (inputs) =>
+      { struct, key, val } = inputs
+      type = struct\type!
+      expected = type\get key.result!
+
+      if expected ~= val\type!
+        msg = string.format "expected value for key '%s' to be %s, not %s",
+                            key.result!, expected, val\type!
+        error Error 'argument', msg
+
+      type
+
+    tick: =>
+      { struct, key, val } = @unwrap_all!
+
+      struct = {k,v for k,v in pairs struct}
+      struct[key] = val
+
+      @out\set struct
+
+insert = Constant.meta
+  meta:
+    name: 'insert'
+    summary: "Insert a new value into a struct."
+    examples: { '(insert struct key val)' }
+    description: "Insert `val` into `struct` at `key`.
+
+`key` has to be a constant expression. This is a pure op, so at most one of
+`struct` and `val` may be a !-stream."
+
+  value: class extends PureOp
+    pattern: any! + key_type + any!
+    type: (inputs) =>
+      { struct, key, val } = inputs
+      type = struct\type!
+      key = key.result!
+
+      if type.types[key]
+        msg = string.format "key '%s' already exists in value of type %s",
+                            key, type
+        error Error 'argument', msg
+
+      types = {k,v for k,v in pairs type.types}
+      types[key] = val\type!
+      Struct types
+
+    tick: =>
+      { struct, key, val } = @unwrap_all!
+
+      struct = {k,v for k,v in pairs struct}
+      struct[key] = val
+
+      @out\set struct
+
+remove = Constant.meta
+  meta:
+    name: 'remove'
+    summary: "Remove values from a struct."
+    examples: { '(remove struct key)' }
+    description: "Removes the value at index `key` from `struct`.
+
+`key` has to be a constant expression."
+
+  value: class extends PureOp
+    pattern: any! + key_type
+    type: (inputs) =>
+      { struct, key } = inputs
+      type = struct\type!
+      key = key.result!
+
+      -- check key exists
+      type\get key
+
+      types = {k,v for k,v in pairs type.types}
+      types[key] = nil
+      Struct types
+
+    tick: =>
+      { struct, key, val } = @unwrap_all!
+
+      struct = {k,v for k,v in pairs struct}
+      struct[key] = nil
+
+      @out\set struct
+
+Constant.meta
+  meta:
+    name: 'struct'
+    summary: "Utilities for dealing with structs."
+
+  value:
+    :get, :set
+    :insert, :remove