# Mu - 070table.mu

      1 # A table is like an array, except that you can index it with arbitrary types
      2 # and not just non-negative whole numbers.
      3
      4 # incomplete; doesn't handle hash conflicts
      5
      6 scenario table-read-write [
      7   local-scope
      8   tab:&:table:num:num <- new-table 30
      9   run [
     10     put-index tab, 12, 34
     11     60:num/raw, 61:bool/raw <- index tab, 12
     12   ]
     13   memory-should-contain [
     14     60 <- 34
     15     61 <- 1  # found
     16   ]
     17 ]
     18
     19 scenario table-read-write-non-integer [
     20   local-scope
     21   tab:&:table:text:num <- new-table 30
     22   run [
     23     put-index tab, [abc def], 34
     24     1:num/raw, 2:bool/raw <- index tab, [abc def]
     25   ]
     26   memory-should-contain [
     27     1 <- 34
     28     2 <- 1  # found
     29   ]
     30 ]
     31
     32 scenario table-read-not-found [
     33   local-scope
     34   tab:&:table:text:num <- new-table 30
     35   run [
     36     1:num/raw, 2:bool/raw <- index tab, [abc def]
     37   ]
     38   memory-should-contain [
     39     1 <- 0
     40     2 <- 0  # not found
     41   ]
     42 ]
     43
     44 container table:_key:_value [
     45   length:num
     46   capacity:num
     47   data:&:@:table-row:_key:_value
     48 ]
     49
     50 container table-row:_key:_value [
     51   occupied?:bool
     52   key:_key
     53   value:_value
     54 ]
     55
     56 def new-table capacity:num -> result:&:table:_key:_value [
     57   local-scope
     58   load-inputs
     59   result <- new {(table _key _value): type}
     60   data:&:@:table-row:_key:_value <- new {(table-row _key _value): type}, capacity
     61   *result <- merge 0/length, capacity, data
     62 ]
     63
     64 # todo: tag results as /required so that call-sites are forbidden from ignoring them
     65 # then we could handle conflicts simply by resizing the table
     66 def put-index table:&:table:_key:_value, key:_key, value:_value -> table:&:table:_key:_value [
     67   local-scope
     68   load-inputs
     69   hash:num <- hash key
     70   hash <- abs hash
     71   capacity:num <- get *table, capacity:offset
     72   _, hash-key:num <- divide-with-remainder hash, capacity
     73   hash-key <- abs hash-key  # in case hash overflows from a double into a negative integer inside 'divide-with-remainder' above
     74   table-data:&:@:table-row:_key:_value <- get *table, data:offset
     75   x:table-row:_key:_value <- index *table-data, hash-key
     76   occupied?:bool <- get x, occupied?:offset
     77   not-occupied?:bool <- not occupied?:bool
     78   assert not-occupied?, [can't handle collisions yet]
     79   new-row:table-row:_key:_value <- merge true, key, value
     80   *table-data <- put-index *table-data, hash-key, new-row
     81 ]
     82
     83 def index table:&:table:_key:_value, key:_key -> result:_value, found?:bool [
     84   local-scope
     85   load-inputs
     86   hash:num <- hash key
     87   hash <- abs hash
     88   capacity:num <- get *table, capacity:offset
     89   _, hash-key:num <- divide-with-remainder hash, capacity
     90   hash-key <- abs hash-key  # in case hash overflows from a double into a negative integer inside 'divide-with-remainder' above
     91   table-data:&:@:table-row:_key:_value <- get *table, data:offset
     92   x:table-row:_key:_value <- index *table-data, hash-key
     93   empty:&:_value <- new _value:type
     94   result <- copy *empty
     95   found?:bool <- get x, occupied?:offset
     96   return-unless found?
     97   key2:_key <- get x, key:offset
     98   found?:bool <- equal key, key2
     99   return-unless found?
    100   result <- get x, value:offset
    101 ]
    102
    103 def abs n:num -> result:num [
    104   local-scope
    105   load-inputs
    106   positive?:bool <- greater-or-equal n, 0
    107   return-if positive?, n
    108   result <- multiply n, -1
    109 ]