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kmsquire opened this issue Sep 5, 2012 · 2 comments
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Feature Request: filtering in comprehensions #1256

kmsquire opened this issue Sep 5, 2012 · 2 comments

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@kmsquire
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kmsquire commented Sep 5, 2012

Comprehensions' offer an easy-to-understand paradigm for map-like operations:

bases = ['A', 'C', 'G', 'T']
basemap = map(i -> bases[i & 3 + 1], [0:255])
basemap2 = [ bases[i & 3 + 1] for i in 0:255 ]
assert(basemap == basemap2)

Some languages (Python, Scala, at least) add syntax to comprehensions to allow filtering of output values:

# Python
xs = range(1,101)
prime_100 = filter(isprime, xs)  # assumes isprime is defined
prime_100_2 = [x for x in xs if isprime(x)]
assert(prime_100 == prime_100_2)

It would be nice if julia supported a similar syntax.
@JeffBezanson
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Dup of #550.

@kmsquire
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kmsquire commented Sep 5, 2012

Sorry, need to search the issues more carefully...

jishnub added a commit that referenced this issue Apr 23, 2025
@DilumAluthgeBot @jishnub
🤖 [master] Bump the LinearAlgebra stdlib from 1ce8426 to 07725da (#58180
16eca6e 
)

Stdlib: LinearAlgebra
URL: https://github.com/JuliaLang/LinearAlgebra.jl.git
Stdlib branch: master
Julia branch: master
Old commit: 1ce8426
New commit: 07725da
Julia version: 1.13.0-DEV
LinearAlgebra version: 1.12.0(Does not match)
Bump invoked by: @jishnub
Powered by:
[BumpStdlibs.jl](https://github.com/JuliaLang/BumpStdlibs.jl)

Diff:
JuliaLang/LinearAlgebra.jl@1ce8426...07725da

```
$ git log --oneline 1ce8426..07725da
07725da Branch on `Bool` `alpha` in scaling `mul!` (#1286)
61e444d Fix exponentiation with immutable matrix (#1289)
77475c1 Fix `lmul!`/`rmul!` for 0-sized matrices (#1290)
c3d35c0 Test for `versioninfo` with `ENV` variable (#1279)
830ea2f Fit broken matmul test (#1288)
222f7f2 Propagate inbounds in diagzero (#1285)
e65e75c Clean up `herk_wrapper!` and add 5-arg tests (#1254)
ece1962 `versioninfo`: simplify, improve type stability (#1274)
3e525a8 Speicalize `copy!` for triangular, and use `copy!` in `ldiv` (#1263)
763f19f Forward scaling `lmul!`/`rmul!` for `Tridiagonal` to bands (#1284)
2d27d1c Explicit loop in converting `Bidiagonal`/`Tridiagonal` to `Matrix` (#1283)
0671a7b Simplify small Bidiagonal-AbstractVecOrMat multiplication (#1278)
a8fd121 Test for empty `Symmetric` and `BlasFlag.NONE` (#1280)
6e2de14 Remove bounds-checking in `Bidiagonal` `rdiv!` (#1281)
4a8fc62 Test for 5-arg `mul!`
c437beb Test for empty `Symmetric` and `BlasFlag.NONE`
7a891e9 Test for `versioninfo` with `ENV` variable
84fd21b Test for `versioninfo` (#1276)
243efdb `AbstractQ` bugfix: define `Base.IteratorSize` (#1277)
6073f28 Ease inference in `Bidiagonal` divmul tests (#1273)
30cb5d6 Avoid copy in empty bidiag `ldiv!` (#1275)
5d3ef46 Skip symmetry check in converting Symmetric to SymTridiagonal (#1269)
ae5385b Specialize `isreal` for banded matrices (#1271)
0a253be Explicit loop in `_iszero` for strided views (#1264)
3f46f5f `istril`/`istriu` for opposite triangularity (#1265)
cd048eb Tests for `mul!` scaling with mismatched axes (#1266)
26db4c8 Restrict tests to `Number` eltypes
8b21ca6 Tests for `mul!` scaling with mismatched axes
9675c38 Fix minimum band for `UpperTriangular`/`Lowertriangular`
aeeed7d Add unit triangular tests
3e1aaac Add banded tests
7fdfb3b Add tests
d866014 istril/istriu for opposite triangularity
925acef Return view in `_diag` for `Bidiagonal` (#1258)
b1bcca1 Branch on `Bool` `alpha` in diagonal matmul (#1256)
e3e9987 `peakflops`: make `eltype` a static parameter of the method (#1253)
781eb5d `peakflops`: make the element type a static parameter of the method
e53b50c use smaller matrix size in `peakflops` on 32-bit (#1255)
0c87d0d use smaller matrix size in `peakflops` on 32-bit
0cbf85f Check approx equality in bunchkaufman docstring (#1251)
5e53d12 Avoid accessing unset indices in symmetric copyto! (#1244)
e64a3df fix dispatch to herk (#1247)
bfdb742 Destination zeros from eltype in zero-length generic_matvecmul (#1241)
16dedb5 Remove redundant adjoint/transpose methods for Symmetric/Hermitian (#1245)
7f1dfe4 stop assuming that you can mutate data structures in other packages at precompile time (#1252)
```

Co-authored-by: jishnub <[email protected]>
LebedevRI pushed a commit to LebedevRI/julia that referenced this issue May 2, 2025
@DilumAluthgeBot @jishnub @LebedevRI
🤖 [master] Bump the LinearAlgebra stdlib from 1ce8426 to 07725da (Jul…
3746633 
…iaLang#58180)

Stdlib: LinearAlgebra
URL: https://github.com/JuliaLang/LinearAlgebra.jl.git
Stdlib branch: master
Julia branch: master
Old commit: 1ce8426
New commit: 07725da
Julia version: 1.13.0-DEV
LinearAlgebra version: 1.12.0(Does not match)
Bump invoked by: @jishnub
Powered by:
[BumpStdlibs.jl](https://github.com/JuliaLang/BumpStdlibs.jl)

Diff:
JuliaLang/LinearAlgebra.jl@1ce8426...07725da

```
$ git log --oneline 1ce8426..07725da
07725da Branch on `Bool` `alpha` in scaling `mul!` (JuliaLang#1286)
61e444d Fix exponentiation with immutable matrix (JuliaLang#1289)
77475c1 Fix `lmul!`/`rmul!` for 0-sized matrices (JuliaLang#1290)
c3d35c0 Test for `versioninfo` with `ENV` variable (JuliaLang#1279)
830ea2f Fit broken matmul test (JuliaLang#1288)
222f7f2 Propagate inbounds in diagzero (JuliaLang#1285)
e65e75c Clean up `herk_wrapper!` and add 5-arg tests (JuliaLang#1254)
ece1962 `versioninfo`: simplify, improve type stability (JuliaLang#1274)
3e525a8 Speicalize `copy!` for triangular, and use `copy!` in `ldiv` (JuliaLang#1263)
763f19f Forward scaling `lmul!`/`rmul!` for `Tridiagonal` to bands (JuliaLang#1284)
2d27d1c Explicit loop in converting `Bidiagonal`/`Tridiagonal` to `Matrix` (JuliaLang#1283)
0671a7b Simplify small Bidiagonal-AbstractVecOrMat multiplication (JuliaLang#1278)
a8fd121 Test for empty `Symmetric` and `BlasFlag.NONE` (JuliaLang#1280)
6e2de14 Remove bounds-checking in `Bidiagonal` `rdiv!` (JuliaLang#1281)
4a8fc62 Test for 5-arg `mul!`
c437beb Test for empty `Symmetric` and `BlasFlag.NONE`
7a891e9 Test for `versioninfo` with `ENV` variable
84fd21b Test for `versioninfo` (JuliaLang#1276)
243efdb `AbstractQ` bugfix: define `Base.IteratorSize` (JuliaLang#1277)
6073f28 Ease inference in `Bidiagonal` divmul tests (JuliaLang#1273)
30cb5d6 Avoid copy in empty bidiag `ldiv!` (JuliaLang#1275)
5d3ef46 Skip symmetry check in converting Symmetric to SymTridiagonal (JuliaLang#1269)
ae5385b Specialize `isreal` for banded matrices (JuliaLang#1271)
0a253be Explicit loop in `_iszero` for strided views (JuliaLang#1264)
3f46f5f `istril`/`istriu` for opposite triangularity (JuliaLang#1265)
cd048eb Tests for `mul!` scaling with mismatched axes (JuliaLang#1266)
26db4c8 Restrict tests to `Number` eltypes
8b21ca6 Tests for `mul!` scaling with mismatched axes
9675c38 Fix minimum band for `UpperTriangular`/`Lowertriangular`
aeeed7d Add unit triangular tests
3e1aaac Add banded tests
7fdfb3b Add tests
d866014 istril/istriu for opposite triangularity
925acef Return view in `_diag` for `Bidiagonal` (JuliaLang#1258)
b1bcca1 Branch on `Bool` `alpha` in diagonal matmul (JuliaLang#1256)
e3e9987 `peakflops`: make `eltype` a static parameter of the method (JuliaLang#1253)
781eb5d `peakflops`: make the element type a static parameter of the method
e53b50c use smaller matrix size in `peakflops` on 32-bit (JuliaLang#1255)
0c87d0d use smaller matrix size in `peakflops` on 32-bit
0cbf85f Check approx equality in bunchkaufman docstring (JuliaLang#1251)
5e53d12 Avoid accessing unset indices in symmetric copyto! (JuliaLang#1244)
e64a3df fix dispatch to herk (JuliaLang#1247)
bfdb742 Destination zeros from eltype in zero-length generic_matvecmul (JuliaLang#1241)
16dedb5 Remove redundant adjoint/transpose methods for Symmetric/Hermitian (JuliaLang#1245)
7f1dfe4 stop assuming that you can mutate data structures in other packages at precompile time (JuliaLang#1252)
```

Co-authored-by: jishnub <[email protected]>
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@kmsquire @JeffBezanson