> In the first two cases evaluation of pt precedes evaluation of xt while
> in the last three cases xt is evaluated before pt. At the moment I
> cannot say why this happens...
I'm sure that this happens, because in the first two cases arguments
passed to a function (I mean C code, not MathProg) are evaluated in one
order while in the last three cases in some different order. For
example, to add two linear forms the following statement is used in
mpl3.c (see line 4754):
value = linear_comb(mpl,
+1.0, eval_formula(mpl, code->arg.arg.x,
+1.0, eval_formula(mpl, code->arg.arg.y);
where the order in which eval_formula is called depends on the platform.
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