Hi, I'm writing my first real Haskell program and I came up with the following code snippet. --- let x' = x \+ dist \* dir nx' = normal geometry wi = (-1) \* dir in do (p, wo) <- brdfCosSampling reflector nx' wi let color' = p \** color q = min 1 (scalarContribution p) in do sampler <- biasedCoinSampler q (radianceSampler surfaces x' wo (q \* color')) (terminalRadianceSampler surfaces x' nx' ((1-q) \* color')) sampler --- This works just fine but I don't like the way I had to indent the code because of alternating lets and dos. I would like to indent the code more like an imperative code i.e. like this --- let { x' = x \+ dist \* dir ; nx' = normal geometry ; wi = (-1) \* dir ; } in do { (p, wo) <- brdfCosSampling reflector nx' wi ; let { color' = p \** color ; q = min 1 (scalarContribution p) ; } in do { sampler <- biasedCoinSampler q (radianceSampler surfaces x' wo (q \* color')) (terminalRadianceSampler surfaces x' nx' ((1-q) \* color')) ; sampler ; }} --- but without braces and semicolons. Following works also, but is ugly (and probably less efficient?). --- do x' <- return $ x \+ dist \* dir nx' <- return $ normal geometry wi <- return $ (-1) \* dir (p, wo) <- brdfCosSampling reflector nx' wi color' <- return $ p \** color q <- return $ min 1 (scalarContribution p) sampler <- biasedCoinSampler q (radianceSampler surfaces x' wo (q \* color')) (terminalRadianceSampler surfaces x' nx' ((1-q) \* color')) sampler --- Is there some nice trick to do this?
2008/5/12 Lauri Oksanen
Hi,
I'm writing my first real Haskell program and I came up with the following code snippet.
--- let x' = x \+ dist \* dir nx' = normal geometry wi = (-1) \* dir in do (p, wo) <- brdfCosSampling reflector nx' wi let color' = p \** color q = min 1 (scalarContribution p) in do sampler <- biasedCoinSampler q (radianceSampler surfaces x' wo (q \* color')) (terminalRadianceSampler surfaces x' nx' ((1-q) \* color')) sampler ---
This works just fine but I don't like the way I had to indent the code because of alternating lets and dos. I would like to indent the code more like an imperative code i.e. like this
You can use let in a do-block, just don't use "in": do x <- something let y = ... x ... return (x + y) -- Denis
2008/5/12 Lauri Oksanen
Hi,
I'm writing my first real Haskell program and I came up with the following code snippet.
--- let x' = x \+ dist \* dir nx' = normal geometry wi = (-1) \* dir in do (p, wo) <- brdfCosSampling reflector nx' wi let color' = p \** color q = min 1 (scalarContribution p) in do sampler <- biasedCoinSampler q (radianceSampler surfaces x' wo (q \* color')) (terminalRadianceSampler surfaces x' nx' ((1-q) \* color')) sampler
Do-notation already offers what you want. Try this out: do let x' = x \+ dist \* dir nx' = normal geometry wi = (-1) \* dir (p, wo) <- brdfCosSampling reflector nx' wi let color' = p \** color q = min 1 (scalarContribution p) sampler <- biasedCoinSampler q (radianceSampler surfaces x' wo (q \* color')) (terminalRadianceSampler surfaces x' nx' ((1-q) \* color')) sampler
On May 12, 2008, at 11:41 AM, Lauri Oksanen wrote:
let x' = x \+ dist \* dir nx' = normal geometry wi = (-1) \* dir in do (p, wo) <- brdfCosSampling reflector nx' wi let color' = p \** color q = min 1 (scalarContribution p) in do sampler <- biasedCoinSampler q (radianceSampler surfaces x' wo (q \* color')) (terminalRadianceSampler surfaces x' nx' ((1- q) \* color')) sampler
Something like the following should work: do let x' = x \+ dist \* dir let nx' = normal geometry let wi = (-1) \* dir (p, wo) <- brdfCosSampling reflector nx' wi let color' = p \** color let q = min 1 (scalarContribution p) sampler <- biasedCoinSampler q (radianceSampler surfaces x' wo (q \* color')) (terminalRadianceSampler surfaces x' nx' ((1-q) \* color')) sampler - Jake McArthur
participants (4)
-
Alfonso Acosta -
Denis Bueno -
Jake Mcarthur -
Lauri Oksanen