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Jesus jumped-up Christ on a snowmobile. How does that get through testing? "Passing a number to a subroutine can result in the value of the number being change

Jesus jumped-up Christ on a snowmobile. How does that get through testing? "Passing a number to a subroutine can result in the value of the number being changed"?

joemi 10y ago
Old-timers please correct me if I'm wrong, but modern-style full-coverage tests of code weren't trivial to write or add to fortran projects on dec10's...
- ChuckMcM 10y ago
  It was possible to write tests but pass by reference is a "feature" of Fortran IV. A subroutine receives values from the caller through the parameter list; likewise, the subroutine returns values by modifying the variables in the parameter list. Subroutines are invoked in a FORTRAN program as a statement, not an expression. The syntax used is, CALL name(actualParamList) See you modify the parameter to send a return value. Really ancient stuff. And if you're working on hardware that is challenged in not having a "load immediate" instruction for floating point, well you get "optimizations" where the compiler creates what is essentially a pre-initialized variable and uses the address of that when a constant is used.
- PhasmaFelis 10y ago
  I mean, I don't understand how the compiler got out the door if passing an integer to a subroutine caused inexplicable disasters. It seems like ChuckMcM is saying the equivalent of int increment(int x) { x = x + 1; return x; } int y = increment(2); Would blow up your program's concept of 2, and I can't imagine that being missed before sending it out to users. But I've never used Fortran, so I may be seeing false equivalences to structures and practices in modern languages.
nikanj 10y ago
In Java, if you have something like void foo(Integer i) { // Putz with reflection, change value stored in i to something else } main() { foo(150); // Nothing special, you just created an autoboxed integer and then alter its value foo(4); // Java pulls you an Integer from the autoboxing cache, and you do indeed accidentally alter the value of 4. }
- PhasmaFelis 10y ago
  Can you tell me a bit more about reflection and autoboxing, or link to where I can learn myself?

Jesus jumped-up Christ on a snowmobile. How does that get through testing? "Passing a number to a subroutine can result in the value of the number being changed"?

joemi 10y ago

Old-timers please correct me if I'm wrong, but modern-style full-coverage tests of code weren't trivial to write or add to fortran projects on dec10's...

ChuckMcM 10y ago
It was possible to write tests but pass by reference is a "feature" of Fortran IV. A subroutine receives values from the caller through the parameter list; likewise, the subroutine returns values by modifying the variables in the parameter list. Subroutines are invoked in a FORTRAN program as a statement, not an expression. The syntax used is, CALL name(actualParamList) See you modify the parameter to send a return value. Really ancient stuff. And if you're working on hardware that is challenged in not having a "load immediate" instruction for floating point, well you get "optimizations" where the compiler creates what is essentially a pre-initialized variable and uses the address of that when a constant is used.
PhasmaFelis 10y ago
I mean, I don't understand how the compiler got out the door if passing an integer to a subroutine caused inexplicable disasters. It seems like ChuckMcM is saying the equivalent of int increment(int x) { x = x + 1; return x; } int y = increment(2); Would blow up your program's concept of 2, and I can't imagine that being missed before sending it out to users. But I've never used Fortran, so I may be seeing false equivalences to structures and practices in modern languages.

nikanj 10y ago

In Java, if you have something like void foo(Integer i) { // Putz with reflection, change value stored in i to something else } main() { foo(150); // Nothing special, you just created an autoboxed integer and then alter its value foo(4); // Java pulls you an Integer from the autoboxing cache, and you do indeed accidentally alter the value of 4. }

PhasmaFelis 10y ago
Can you tell me a bit more about reflection and autoboxing, or link to where I can learn myself?