rename set_slot

set_slot was clear about the target, but not the source.
Better with reg_to_slot (and soon it’s inverse slot_to_reg)

lib/register/instructions/reg_to_slot.rb

@@ -0,0 +1,35 @@
+module Register
+
+  # RegToSlot moves data into memory from a register.
+  # GetSlot moves data into a register from memory.
+  # Both use a base memory (a register)
+
+  # This is because that is what cpu's can do. In programming terms this would be accessing
+  #  an element in an array, in the case of RegToSlot setting the register in the array.
+
+  # btw: to move data between registers, use RegisterTransfer
+
+  class RegToSlot < Setter
+
+    # If you had a c array and index offset
+    # the instruction would do array[index] = register
+    # So RegToSlot means the register (first argument) moves to the slot (array and index)
+
+    # def initialize source , register , array , index
+    # super
+    # end
+    # attr_accessor :register , :array , :index
+
+  end
+
+  # Produce a RegToSlot instruction.
+  # From and to are registers or symbols that can be transformed to a register by resolve_to_register
+  # index resolves with resolve_index.
+  def self.reg_to_slot source , from , to , index
+    from = resolve_to_register from
+    index = resolve_index( to , index)
+    to = resolve_to_register to
+    RegToSlot.new( source, from , to , index)
+  end
+
+end