# Preface:

This document is a scratch space for the design of the switch action.
It may be out of date and is kept around for posterity.

.syntax:
----
(switch
  (or a b c) (cmd <cmd1>) break
  (and a b (or c d)) (cmd <cmd2>) fallthrough
  (and a b (or c d) (or e f)) fallthrough
  ()
)
----


.opcode format examples:
----
(or a b c)
OR-4 a b c

(and a b (or c d))
AND-6 a b OR-6 c d

(and a b (or c d) (or e f))
AND-9 a b OR-6 c d OR-9 e f
----

.opcodes:
----
key: all values < 1024
OR/AND: OP & 0xF000
  OR : 0x1000
  AND: 0x2000
  length: OP & 0x0FFF
----

.Rough algorithm for opcodes:
----
value=true
push first opcode
WHILE stack is not empty
  WHILE index <= ending_index
    switch
      opcode:
        push, continue
      key(OR):
        value=true: skip to index, pop
        value=false: continue
      key(AND):
        value=true: continue
        value=false: skip to index, pop
  pop
  switch
    current_value(OR):
      value=true: skip to index, pop
      value=false: continue
    current_value(AND):
      value=true: continue
      value=false: skip to index, pop
return value
----

.statestruct:
----
  value
  current_index
  current_end_index
  current_op
  stack (op, ending_index)
----

.rough sequence 1:
----
pressed:       y y      y y      y y
opcodes: AND-9 a b OR-6 c d OR-9 e f

index: 0
  push: AND-9
  stack: AND-9

index: 1
  val: true

index: 2
  val: true

index: 3
  push: OR-6
  stack: AND-9 OR-6

index: 4
  val: true
  skip to 6
  pop
  stack: AND-9

index: 6
  push: OR-9
  stack: AND-9 OR-9

index: 7
  val: true
  skip to 9
  pop
  stack: AND-9-true

index 9:
  pop
  stack: empty
  return val: true
----

.rough sequence 2:
----
pressed:       y y      n n      y y
opcodes: AND-9 a b OR-6 c d OR-9 e f

index: 0
  push: AND-9
  stack: AND-9

index: 1
  val: true

index: 2
  val: true

index: 3
  push: OR-6
  stack: AND-9 OR-6
  val: true

index: 4
  val: false

index: 5
  val: false

index: 6
  val: false
  pop
  stack: AND-9
  skip to 9
  pop
  stack: empty
  return val: false
----

.rough sequence 3:
----
pressed:       n y      n n      y y
opcodes: AND-9 a b OR-6 c d OR-9 e f

index: 0
  push: AND-9
  stack: AND-9

index: 1
  val: false
  skip to 9
  pop
  stack: empty
  return val: false
----


.pseudo code again:
----
let mut value = true
let mut current_index = 1
let mut current_end_index = first_opcode - end_index
let mut current_op = OR
while current_index < slice_length {
  if index >= current_end_index:
    if stack is empty:
      break
    else:
      pop stack to current_op and current_end_index
      switch
        current_value(OR):
          value=true: skip to current_end_index; continue
        current_value(AND):
          value=false: skip to current_end_index; continue
  switch
    opcode:
      push (current_end_index,current_op)
      update (current_end_index,current_op) with opcode
    key(OR):
      value=true: skip to current_end_index; continue
      value=false
    key(AND):
      value=true
      value=false: skip to current_end_index; continue
  current_index++;
}
return value
----