Hi Elias,
It seems that there would be a substantial performance hit using C++ object management to construct your workspace. I haven't run any benchmarks before, but perhaps a quick comparison with APL2 would be useful at this point.
Let's make a little function that does something 100 times.
∇DO100[⎕]∇
∇
[0] DO100 X;I
[1] I←¯1
[2] L1:→((I←I+1)≥100)/0
[3] ⍎X
[4] →L1
∇ 2015-08-20 21.00.29.850 (GMT-7)
And another little function that prints out the number of seconds something takes.
∇TIME[⎕]∇
∇
[0] TIME X;TS
[1] TS←⎕TS
[2] ⍎X
[3] (⍕(24 60 60 1000⊥¯4↑⎕TS-TS)÷1000),' Seconds.'
∇ 2015-08-20 21.01.09.470 (GMT-7)
And an array of a million floats.
And a 100x100 boolean identity matrix
B←100 100⍴101↑1=1
[IBM APL2]
TIME 'DO100 ''A←⍉A'''
2.391 Seconds.
TIME 'DO100 ''B←B∨.∧B'''
7.591 Seconds.
TIME 'DO100 ''C←≠\B'''
0.197 Seconds.
[GNU APL]
TIME 'DO100 ''A←⍉A'''
54.987 Seconds.
TIME 'DO100 ''B←B∨.∧B'''
13.325 Seconds
TIME 'DO100 ''C←≠\B'''
59.361 Seconds.
That's actually not too horrible, considering what it's having to do.