|
|
Weak Head Normal Form
<reduction, lambda calculus> (WHNF) A lambda expression is
in weak head normal form (WHNF) if it is a head normal form
(HNF) or any lambda abstraction. I.e. the top level is not
a redex.
The term was coined by Simon Peyton Jones to make explicit
the difference between head normal form (HNF) and what
graph reduction systems produce in practice. A lambda
abstraction with a reducible body, e.g.
\ x . ((\ y . y+x) 2)
is in WHNF but not HNF. To reduce this expression to HNF
would require reduction of the lambda body:
(\ y . y+x) 2 --> 2+x
Reduction to WHNF avoids the name capture problem with its
need for alpha conversion of an inner lambda abstraction and
so is preferred in practical graph reduction systems.
The same principle is often used in strict languages such as
Scheme to provide call-by-name evaluation by wrapping an
expression in a lambda abstraction with no arguments:
D = delay E = \ () . E
The value of the expression is obtained by applying it to the
empty argument list:
force D = apply D ()
= apply (\ () . E) ()
= E
(1994-10-31)
Try this search on OneLook / Google
Nearby terms:
WDASM « WDM « WE « Weak Head Normal Form » weakly typed » weak typing » weasel
This article was derived from the Free Online Dictionary of Computers and is available under ther terms of the GNU Free Documentation License.
Snap! Mortgage MasterSnap! Mortgage Master Save wear on your sanity and your wallet. With Snap! Mortgage Master, the educational software tool that easily guides you through the often nerve-wracking process of home financing. Windows 95/98/ME/2000/XP More ...
Hewlett Packard 1010 Fax/Phone/Convenience CopierHewlett Packard 1010 Fax/Phone/Convenience Copier **Hewlett Packard fax 1010xi Fax, Phone, Convenience Copier **This HP fax 1010xi with its integrated, space savingfax and phone is ideal for a personal office! TheHP fax 1010xi can send faxes up to 14.4 Kbps,delivers crisp faxes, and prints incoming faxesat up to 300 x 300 dpi. Stock up today on thisquick and reliable HP fax 1010xi fax, phone,convenience copier!General Features:- Charcoal Profile- Type of unit: Inkjet desktop facsimile transceiver- Duty cycle: 500 pages per month - Compatibility: ITU Group3 - Fax Speed: up to 14.4 Kbps - Maximum number of copies: 50- Reduce/Enlarge percentage: 50 - 125 percent - Maximum copying speed: 2 copies per minute (cpm) - Scanning method: Contact image sensor (CIS) - Speed dials: 50 - Grey scale levels: 64 - User memory capacity: 0.5 Mb (40 pages at 4 percent coverage on A4 paper) Resolution:- Scan: 200 x 200 - Copy: Standard or Fine: 300 x 300, Super Fine or Photo: 600 x 300 - Fax: Standard: 98 x 203, Fine: 196 x 203, Super Fine: 392 x 203 Power Consumption:- Standby mode: 5 Wh - Printing mode: maximum 15 Wh - Voltage: 110 - 127 - Frequency: 50 - 60 Hz Regulatory Approvals:- ULPlain Box Includes:- HP fax 1010 Refurbished fax, phone, convenience copier- HP 20 black inkjet cartridge- Setup poster and user guide- Power cord and Telephone cord- Telephone handset and handset cord- Plastic Document tray guideNotes:- HP fax 1010 series Model: 1010xi- P/N: C9271AR- UPC: 8 08736 89350 2- This product is covewred by direct manufacturer warrantythat may be valid in the US. Please contact our sales departement prio to purchase if you have any questionsregarding the warranty of this product. Compatibility/Requirements/Disclosures: ** Requirements *** Available Phone line* Available Power Outlet Informational Links: http://h10025.www1.hp.com/ewfrf/wc/document?product=295753&lang=en&lc=en&cc=us&dlc ... More ...
Video PokerVideo Poker Looking for fast-paced, small-screen Dealer's Choice card play? Then ante up for Video Poker, the interactive game suite that brings the casino lounge to choice multiple games including Jacks or Better, Deuces Wild, Jokers Wild, Double Premium Poker, and Triple Premium Poker. Windows 95/98/ME/2000/XP More ...
Blue's Clues PreschoolBlue's Clues Preschool Miss Marigold has a long checklist of places for kids to visit. Adventure with Blue to the grocery, gift, and music stores, as well as to the bakery and the library. Each venue offers something special for Blue and kids to bring back to Circle Time. Ages 3-5. Windows 98/ME/2000/XP and Mac More ...
Amplified Portable Foldable Speakers (White)Amplified Portable Foldable Speakers (White) ** Amplified Portable Foldable Compact Speakers (White) **This PA-211 Amplified portable compact speaker features a unique fold-up design for maximum portability and a built-in amplifier for great sound quality. This Amplified foldable speaker is ideal for MP3 players, CD players and Notebook computers! Its lightweight and portable so you can take it with you. Order yours today!General Features:- White profile- Unique fold-up design for maximum portability- Amplified Portable Speakers- Ideal for CD, MD, MP3 Player, Notebook Computers- Runs on Three (3) AA batteries (not included)- Output Power: 0.5W- Frequency Response: 200 Hz ~ 12 KHz- Speaker: 57 mm speaker, 8 ohms- Plug: Gold-Plated 3.5 mm stereo- Power On/Off switch- Volume Control dial Dimensions:- Folded-Up (Flat): 5" x 3" x 1.75: (L x W x H)- Opened-Up (Upright): 10" x 0.75" x 3.5" (L x W x H)Retail Package Includes:- Amplified Fold-Up Portable Speaker- Carrying PouchNotes:- Model: PA-211 Compatibility/Requirements/Disclosures: ** Requirements *** Three (3) AA Batteries* Available 3.5 mm stereo speaker jack More ...
French Visual Personal InterpreterFrench Visual Personal Interpreter Finally - an interpreter that work as hard as you do! The days of thumbing through awkward English-French dictionaries are over, thanks to the French Virtual Personal Interpreter (French VPI). Windows 95/98/ME/NT/2000/XP More ...
|
