How do you use matrices in Nimrod?

Question

I found this project on GitHub; it was the only search term returned for "nimrod matrix". I took the bare bones of it and changed it a little bit so that it compiled without errors, and then I added the last two lines to build a simple matrix, and then output a value, but the "getter" function isn't working for some reason. I adapted the instructions for adding properties found here, but something isn't right. Here is my code so far. I'd like to use the GNU Scientific Library from within Nimrod, and I figured that this was the first logical step. ``` type TMatrix*[T] = object transposed: bool dataRows: int dataCols: int data: seq[T] proc index[T](x: TMatrix[T], r,c: int): int {.inline.} = if r<0 or r>(x.rows()-1): raise newException(EInvalidIndex, "matrix index out of range") if c<0 or c>(x.cols()-1): raise newException(EInvalidIndex, "matrix index out of range") result = if x.transposed: c*x.dataCols+r else: r*x.dataCols+c proc rows*[T](x: TMatrix[T]): int {.inline.} = ## Returns the…

Accepted Answer

I'd like to first point out that the matrix library you refer to is three years old. For a programming language in development that's a lot of time due to changes, and it doesn't compile any more with the current Nimrod git version:

```
$ nimrod c matrix
...
private/tmp/n/matrix/matrix.nim(97, 8) Error: ']' expected
```

It fails on the double array accessor, which seems to have changed syntax. I guess your attempt to create a double `[][]` accessor is problematic, it could be ambiguous: are you accessing the double array accessor of the object or are you accessing the nested array returned by the first brackets? I had to change the `proc` to the following:

```
proc `[]`*[T](x: TMatrix[T], r,c: int): T =
```

After that change you also need to change the way to access the matrix. Here's what I got:

```
for x in 0 .. <2:
  for y in 0 .. <2:
    echo "x: ", x, " y: ", y, " = ", m[x,y]
```

Basically, instead of specifying two bracket accesses you pass all the parameters inside a single bracket. That code generates:

```
x: 0 y: 0 = 1
x: 0 y: 1 = 2
x: 1 y: 0 = 3
x: 1 y: 1 = 4
```

With regards to finding software for Nimrod, I would like to recommend you using Nimble, Nimrod's package manager. Once you have it installed you can search available and maintained packages. The command `nimble search math` shows two potential packages: linagl and extmath. Not sure if they are what you are looking for, but at least they seem more fresh.

How do you use matrices in Nimrod?

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