Root finding

[Carrico, Paul]

Dear all,
 
is it a stupid question in asking why the condition herebellow leads to
an error ?
 
Nota :  
- I just want to keep the integer values resulting from the root finding
... 
- (if + r_) leads to en error while the formula works T2_ = T0_ / (1 +
0.5*(gamma_ - 1)*r_(1)^2) ??


Another (stupid) question : 
-  is it possible to perform a root finding with real exponents instead
of integer ones ? if so how ?
- the exponents typically look like [ 0.5*(gamma_ + 1) / (gamma_ - 1) ]:

 
Thanks everybody for (previous and futur) advices
 
Paul
 
######################################################################"
x = poly(0,"x");
p = 1 + coef_1*x + coef_2*x^2 + coef_4*x^4 + coef_6*x^6 ;
r_ = roots(p);

if ( r_(1) < 1) then
    Mach2 = r_(1);
    Mach3 = r_(2);
else
    Mach2 = r_(2);
    Mach3 = r_(1);
end
 
// Before the sonic col
P2_ = P0_ / (1 + 0.2*r_(1)^2)^3.5;
T2_ = T0_ / (1 + 0.5*(gamma_ - 1)*Mach2^2);

// After the sonic col
P3_ = P0_ / (1 + 0.2*r_(2)^2)^3.5;
T3_ = T0_ / (1 + 0.5*(gamma_ - 1)*Mach3^2);

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