survreg (survival) reports erroneous results for left-censored data (PR#2287)

Thomas,
you were right. It works now. This is what I get with Carbon R and the 
patched survival package.
I will upload a patched version of survivalLib. Can you please fix 
SurvS.h sources?
Stefano


 > survreg(Surv(c(0,1,-1),c(T,T,F),type='left')~1,dist='gaussian')
Call:
survreg(formula = Surv(c(0, 1, -1), c(T, T, F), type = "left") ~
     1, dist = "gaussian")

Coefficients:
(Intercept)
  -0.2321569

Scale= 1.161135

Loglik(model)= -4.1   Loglik(intercept only)= -4.1
n= 3

 I think it's a problem with the erfc macro in survS.h, which is 
defined
as
#ifndef erfc
#define erfc(x) 2*pnorm5(-x*M_SQRT2,0,1,1,0)
#endif

The problem is that in survreg2.c we call erf(-z/ROOT_2), which 
expands to
2*pnorm5(--z/ROOT_2*SQRT2,0,1,1,0), and the -- becomes a predecrement
operator.   I hate macros.

If so, the fix would be
#ifndef erfc
#define erfc(x) 2*pnorm5(-(x)*M_SQRT2,0,1,1,0)
#endif

	-thomas

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