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Passing array by reference in RobotC 1.05

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Passing array by reference in RobotC 1.05

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mcrosbie

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Joined: Sun Jul 22, 2007 6:32 pm
Posts: 16
Location: Ireland

Passing array by reference in RobotC 1.05

Hi,

Is it possible to pass an array by reference in RobotC 1.05?

I'm attempting to pass an array of ints into a function to initialise the array. At a later point I will have another function to update the array with sensor readings.

The following code refuses to compile, with an error on the line where I dereference the pToArray argument: **Error**:Array specifier invalid for variable 'pToArray'


	Code: void initialiseArray(int &pToArray, tSensors sensorToRead) { int i; for(i=0; i < kNumSamples; i++) { pToArray[i] = SensorValue[sensorToRead]; ...... } }

I have also tried using


	Code: void initialiseArray(int &pToArray[], tSensors sensorToRead)

and just plain old


	Code: void initialiseArray(int pToArray[], tSensors sensorToRead)

to declare the function. None of these options will compile.

This code would be called as:


	Code: const int kNumSamples = 50; int sonarSensorReadings[kNumSamples]; ... initialiseArray(sonarSensorReadings, S4);

Is it possible to pass arrays by reference, and if so what is the correct syntax for doing so?

Many thanks,
Mark

Sun Jul 22, 2007 6:50 pm

dtrotzjr

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Joined: Sat Jun 16, 2007 6:24 pm
Posts: 14

The easiest way I know how to do this is by wrapping your array in a struct and passing that in. Its not the prettiest code, but it does accomplish what you want, and you may have more you want to encapsulate in that structure at which point it will make more sense to use a struct.

Maybe someone has a better idea, but thats my best first try.


	Code: #define BSIZE 100 typedef struct { int size = BSIZE; int array[BSIZE]; } BoundArr; void initArray(BoundArr a) { for(int i = 0; i < a.size; i++) a.array[i] = i*2; } void printArray(BoundArr a) { for(int i = 0; i < a.size; i++){ wait1Msec(100); nxtDisplayTextLine(1, "a.array[%d] = %d", i, a.array[i]); } } task main() { BoundArr a; initArray(a); printArray(a); }

I hope that helps. This is the second C related question this weekend. It might be smart if RobotC used an extension other than .c (perhaps .rc) to more explicitly set itself apart from C.

-- David Trotz

Sun Jul 22, 2007 7:18 pm

mcrosbie

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Joined: Sun Jul 22, 2007 6:32 pm
Posts: 16
Location: Ireland

Thanks David,

That seems to have fooled the compiler for now! It also allows me to encapsulate more of the data related to the array.

Regards,
Mark

Mon Jul 23, 2007 10:19 am

Dick Swan

Creator

Joined: Fri Feb 09, 2007 9:21 am
Posts: 615

This is is bug. It is fixed in version 1.07.

Note that you presently cannot declare array indices explicitly on a procedure parameter. But you can declare a 'typedef' for an array type and then have the type of a procedure parameter be a typedef. See the following code snippet.

I corrected a code generation bug with this that I don't think occurs in the "struct' trick mentioned earlier in this thread.


	Code: typedef int tArray[10][10]; tArray yy; void testFunction(tArray &xx, const int nAdjust) { int i; int j; for (i = 0; i < 10; ++i) for (j = 0; j < 10; ++j) { xx[i][j] = nAdjust; } return; } task main() { int i; for (i = 0; i < 30000; i += 100) { testFunction(yy, i); wait1Msec(500); } return; }

Thu Aug 02, 2007 7:08 pm

suwandi_wieming

Rookie

Joined: Mon Sep 17, 2007 5:31 am
Posts: 28
Location: Indonesia

hey....

I try the program but it can't work...
how can it be???
can you teach me the program use "wait until"...
it's difficult for me...
and how you all use about using set sensor mode????
thanks...

Mon Sep 17, 2007 11:41 pm

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