Update docs

docs/syntax.md

@@ -362,3 +362,23 @@ Looks in the path $GROUND_LIBS/`$libraryName`.grnd for the library. ($GROUND_LIB
 Attempts to import a shared library written in a compiled language like C or C++ for usage within the current program.
 
 Looks in the path $GROUND_LIBS/`$libraryName`.so for the library. ($GROUND_LIBS is a system environment variable.)
+
+### Data Structures
+
+#### struct -structName
+
+Creates a new struct which can be initialised. Until the endstruct keyword, the only valid instructions are init, set, fun, endfun, struct, and endstruct.
+
+Any value created inside the struct will be added to the struct.
+
+#### endstruct
+
+Ends the creation of a struct.
+
+#### getfield $object &fieldName &outputVar
+
+Gets a field from an initialised object. fieldName must be a valid name of a field in the object. Errors if the field does not exist. 
+
+#### setfield &object &fieldName $value
+
+Sets a field to a new value in the object. The value must be of the same type as the field's old value.