Database.HaskellDB.BoundedList

haskelldb-0.12: SQL unwrapper for Haskell.

Portability	non-portable
Stability	experimental
Maintainer	haskelldb-users@lists.sourceforge.net

Description

The main idea of bounded lists is to create lists with predetermined maximum size.

BoundedList is a simple, fast and type safe approach to implementing this idea. The implementation is based on inductive instances, making it very easy to expand with new bounds. A new bound only requires one instance of size and two instances of Less.

BoundedList works as follows. Every bound is build up by declaring a data-type representing the new bound. The instance of size only returns the size as an Int. The first instance of Less is for telling the typechecker that this bound is greater than the largest smaller bound. The second instance of Less is used by the typechecker to construct a chain of instances if there is no hardcoded instance available. This way the type checker can determine if a bound is smaller/greater then any other bound.

This inductive approach gives the complexity O(n) on the number of instances and very short type checking times compared to an O(n^2) implementation.

BoundedList also comes with a few utility function for manipulation an contructing bounded lists.

To be noted: Since each bound is a unique type: Explicit shrink and/or grow is needed before using (==). BoundedList does not have an instance of Ordering. (This might change)

Synopsis

shrink :: (Size n, Size m) => BoundedList a n -> Maybe (BoundedList a m)

grow :: LessEq n m => BoundedList a n -> BoundedList a m

trunc :: Size n => [a] -> BoundedList a n

listBound :: Size n => BoundedList a n -> Int

toBounded :: Size n => [a] -> Maybe (BoundedList a n)

fromBounded :: Size n => BoundedList a n -> [a]

class Size n

data BoundedList a n

data N0

data N1

data N2

data N3

data N4

data N5

data N6

data N7

data N8

data N9

data N10

data N11

data N12

data N13

data N14

data N15

data N16

data N17

data N18

data N19

data N20

data N21

data N22

data N23

data N24

data N25

data N26

data N27

data N28

data N29

data N30

data N31

data N32

data N33

data N34

data N35

data N36

data N37

data N38

data N39

data N40

data N41

data N42

data N43

data N44

data N45

data N46

data N47

data N48

data N49

data N50

data N51

data N52

data N53

data N54

data N55

data N56

data N57

data N58

data N59

data N60

data N61

data N62

data N63

data N64

data N65

data N66

data N67

data N68

data N69

data N70

data N71

data N72

data N73

data N74

data N75

data N76

data N77

data N78

data N79

data N80

data N81

data N82

data N83

data N84

data N85

data N86

data N87

data N88

data N89

data N90

data N91

data N92

data N93

data N94

data N95

data N96

data N97

data N98

data N99

data N100

data N101

data N102

data N103

data N104

data N105

data N106

data N107

data N108

data N109

data N110

data N111

data N112

data N113

data N114

data N115

data N116

data N117

data N118

data N119

data N120

data N121

data N122

data N123

data N124

data N125

data N126

data N127

data N128

data N129

data N130

data N131

data N132

data N133

data N134

data N135

data N136

data N137

data N138

data N139

data N140

data N141

data N142

data N143

data N144

data N145

data N146

data N147

data N148

data N149

data N150

data N151

data N152

data N153

data N154

data N155

data N156

data N157

data N158

data N159

data N160

data N161

data N162

data N163

data N164

data N165

data N166

data N167

data N168

data N169

data N170

data N171

data N172

data N173

data N174

data N175

data N176

data N177

data N178

data N179

data N180

data N181

data N182

data N183

data N184

data N185

data N186

data N187

data N188

data N189

data N190

data N191

data N192

data N193

data N194

data N195

data N196

data N197

data N198

data N199

data N200

data N201

data N202

data N203

data N204

data N205

data N206

data N207

data N208

data N209

data N210

data N211

data N212

data N213

data N214

data N215

data N216

data N217

data N218

data N219

data N220

data N221

data N222

data N223

data N224

data N225

data N226

data N227

data N228

data N229

data N230

data N231

data N232

data N233

data N234

data N235

data N236

data N237

data N238

data N239

data N240

data N241

data N242

data N243

data N244

data N245

data N246

data N247

data N248

data N249

data N250

data N251

data N252

data N253

data N254

data N255

data N65535

Documentation

shrink :: (Size n, Size m) => BoundedList a n -> Maybe (BoundedList a m)