selection syntax

.gitignore

@@ -6,3 +6,4 @@ docs/site/
 .DS_Store
 benchmark/tune.json
 Manifest.toml
+*.swp

Test/Project.toml

@@ -0,0 +1 @@
+[deps]

docs/src/documentation.md

@@ -20,7 +20,7 @@ downloadpdb("1EN2")
 
 To parse a PDB file into a Structure-Model-Chain-Residue-Atom framework:
 
-```julia
+```julia-repl
 julia> struc = read("/path/to/pdb/file.pdb", PDB)
 ProteinStructure 1EN2.pdb with 1 models, 1 chains (A), 85 residues, 754 atoms
 ```
@@ -29,7 +29,7 @@ mmCIF files can be read into the same data structure with `read("/path/to/cif/fi
 The keyword argument `gzip`, default `false`, determines if the file is gzipped.
 If you want to read an mmCIF file into a dictionary to query yourself (e.g. to access metadata fields), use [`MMCIFDict`](@ref):
 
-```julia
+```julia-repl
 julia> mmcif_dict = MMCIFDict("/path/to/cif/file.cif")
 mmCIF dictionary with 716 fields
 
@@ -144,6 +144,7 @@ This can be changed by setting `expand_disordered` to `true` in [`collectatoms`]
 
 Selectors are functions passed as additional arguments to these functions.
 Only elements that return `true` when passed to all the selector are retained.
+See also the selection syntax [described below](@ref String-selection-syntax).
 For example:
 
 | Command                                                 | Action                                                            | Return type                |
@@ -199,7 +200,7 @@ collectatoms(struc, at -> x(at) < 0)
 [`countatoms`](@ref), [`countresidues`](@ref), [`countchains`](@ref) and [`countmodels`](@ref) can be used to count elements with the same selector API.
 For example:
 
-```julia
+```julia-repl
 julia> countatoms(struc)
 754
 
@@ -215,7 +216,7 @@ julia> countatoms(struc, expand_disordered=true)
 
 The amino acid sequence of a protein can be retrieved by passing an element to [`LongAA`](@ref) with optional residue selectors:
 
-```julia
+```julia-repl
 julia> LongAA(struc['A'], standardselector)
 85aa Amino Acid Sequence:
 RCGSQGGGSTCPGLRCCSIWGWCGDSEPYCGRTCENKCW…RCGAAVGNPPCGQDRCCSVHGWCGGGNDYCSGGNCQYRC
@@ -227,7 +228,7 @@ See [BioSequences.jl](https://github.com/BioJulia/BioSequences.jl) and [BioAlign
 [`LongAA`](@ref) is an alias for `LongSequence{AminoAcidAlphabet}`.
 For example, to see the alignment of CDK1 and CDK2 (this example also makes use of Julia's [broadcasting](https://docs.julialang.org/en/v1/manual/arrays/#Broadcasting-1)):
 
-```julia
+```julia-repl
 julia> struc1, struc2 = retrievepdb.(["4YC6", "1HCL"])
 2-element Array{ProteinStructure,1}:
  ProteinStructure 4YC6.pdb with 1 models, 8 chains (A,B,C,D,E,F,G,H), 1420 residues, 12271 atoms
@@ -270,6 +271,99 @@ PairwiseAlignmentResult{Int64, LongAA, LongAA}:
 In fact, [`pairalign`](@ref) is extended to carry out the above steps and return the alignment by calling `pairalign(struc1["A"], struc2["A"], standardselector)` in this case.
 `scoremodel` and `aligntype` are keyword arguments with the defaults shown above.
 
+## String selection syntax
+
+!!! compat
+    The string-selection syntax was introduced in version 3.13.
+
+`BioStructures.jl` exports the `sel` macro that provides a practical way to collect atoms from a structure
+using a natural selection syntax. It must be used as: 
+```julia
+collectatoms(struc, sel"selection string")
+```
+where `struc` is the input structure and `selection string` defines the atoms to be selected, with the 
+operators and keyword defined below.
+
+For example:
+
+```julia-repl
+julia> struc = retrievepdb("4YC6")
+[ Info: Downloading file from PDB: 4YC6
+ProteinStructure 4YC6.pdb with 1 models, 8 chains (A,B,C,D,E,F,G,H), 1420 residues, 12271 atoms
+
+julia> collectatoms(struc, sel"name CA and resnumber <= 5")
+24-element Vector{AbstractAtom}:
+ Atom CA with serial 2, coordinates [17.363, 31.409, -27.535]
+ Atom CA with serial 10, coordinates [20.769, 32.605, -28.801]
+ ⋮
+ Atom CA with serial 11096, coordinates [-8.996, 6.094, -29.097]
+```
+
+There are also macro-keywords to select groups of atoms with specific properties. For example:
+
+```julia-repl
+julia> ats = collectatoms(struc, sel"acidic and name N")
+188-element Vector{AbstractAtom}:
+ Atom N with serial 9, coordinates [19.33, 32.429, -28.593]
+ Atom N with serial 18, coordinates [21.056, 33.428, -26.564]
+ ⋮
+ Atom N with serial 11603, coordinates [-0.069, 21.516, -32.604]
+
+julia> resname.(ats)
+188-element Vector{SubString{String}}:
+ "GLU"
+ "ASP"
+ ⋮
+ "GLU"
+```
+
+The current supported operators are:
+
+| Operators                   | Acts on                             |
+| :-------------------------- | :---------------------------------- |
+| `=`, `>`, `<` `>=`, `<=`    | Properties with real values.        |
+| `and`, `or`, `not`          | Selections subsets.                 | 
+
+The keywords supported are:
+
+
+| Keyword                     | Input type   | Selects for          |
+| :-------------------------- | :-----------:|:---------------------|
+|  `index`                     | `Int`         | `serial`              |
+|  `serial`                    | `Int`         | `serial`              |
+|  `resnumber`                 | `Int`         | `resnumber`           |
+|  `resnum`                    | `Int`         | `resnumber`           |
+|  `resid`                     | `Int`         | `resid`               |
+|  `occupancy`                 | `Real`        | `occupancy`           |
+|  `beta`                      | `Real`        | `tempfactor`          |
+|  `tempfactor`                | `Real`        | `tempfactor`          |
+|  `model`                     | `Int`         | `modelnumber`         |
+|  `modelnumber`               | `Int`         | `modelnumber`         |
+|  `name`                      | `String`      | `atomname`            |
+|  `atomname`                  | `String`      | `atomname`            |
+|  `segname`                   | `String`      | `segname`             |
+|  `resname`                   | `String`      | `resname`             |
+|  `chain`                     | `String`      | `chainid`             |
+|  `chainid`                   | `String`      | `chainid`             |
+|  `element`                   | `String`      | `element`             |
+|  `water`                     |               | Water molecules       |
+|  `protein`                   |               | Protein atoms         |
+|  `polar`                     |               | Polar residues        |
+|  `nonpolar`                  |               | Non-polar residues    |
+|  `basic`                     |               | Basic residues        |
+|  `acidic`                    |               | Acidic residues       |
+|  `charged`                   |               | Charged residues      |
+|  `aliphatic`                 |               | Aliphatic residues    |
+|  `aromatic`                  |               | Aromatic residues     |
+|  `hydrophobic`               |               | Hydrophobic residues  |
+|  `neutral`                   |               | Neutral residues      |
+|  `backbone`                  |               | Backbone atoms        |
+|  `heavyatom`                 |               | Heavy atoms           |
+|  `disordered`                |               | Disordered atoms      |
+|  `sidechain`                 |               | Side-chain atoms      |
+|  `all`                       |               | all atoms             |
+
+
 ## Spatial calculations
 
 Various functions are provided to calculate spatial quantities for proteins:
@@ -304,7 +398,7 @@ The [`omegaangle`](@ref) and [`phiangle`](@ref) functions measure the angle betw
 The [`psiangle`](@ref) function measures between the given index and the one after.
 For example:
 
-```julia
+```julia-repl
 julia> distance(struc['A'][10], struc['A'][20])
 10.782158874733762
 
@@ -325,7 +419,7 @@ julia> rad2deg(psiangle(struc['A'], 50))
 [`ContactMap`](@ref) can also be given two structural elements as arguments, in which case a non-symmetrical 2D array is returned showing contacts between the elements.
 The underlying `BitArray{2}` for [`ContactMap`](@ref) `contacts` can be accessed with `contacts.data` if required.
 
-```julia
+```julia-repl
 julia> contacts = ContactMap(collectatoms(struc['A'], cbetaselector), 8.0)
 Contact map of size (85, 85)
 ```
@@ -387,7 +481,7 @@ The contacting elements in a molecular structure form a graph, and this can be r
 This extends `MetaGraph` from [MetaGraphs.jl](https://github.com/JuliaGraphs/MetaGraphs.jl), allowing you to use all the graph analysis tools in [Graphs.jl](https://github.com/JuliaGraphs/Graphs.jl).
 For example:
 
-```julia
+```julia-repl
 julia> using Graphs, MetaGraphs
 
 julia> mg = MetaGraph(collectatoms(struc["A"], cbetaselector), 8.0)
@@ -488,7 +582,7 @@ In this case download the mmCIF file or MMTF file instead.
 
 To parse an existing PDB file into a Structure-Model-Chain-Residue-Atom framework:
 
-```julia
+```julia-repl
 julia> struc = read("/path/to/pdb/file.pdb", PDB)
 ProteinStructure 1EN2.pdb with 1 models, 1 chains (A), 85 residues, 754 atoms
 ```
@@ -506,15 +600,15 @@ Various options can be set through optional keyword arguments when parsing PDB/m
 
 Use [`retrievepdb`](@ref) to download and parse a PDB file into a Structure-Model-Chain-Residue-Atom framework in a single line:
 
-```julia
+```julia-repl
 julia> struc = retrievepdb("1ALW", dir="path/to/pdb/directory")
 INFO: Downloading PDB: 1ALW
 ProteinStructure 1ALW.pdb with 1 models, 2 chains (A,B), 346 residues, 2928 atoms
 ```
 
 If you prefer to work with data frames rather than the data structures in BioStructures, the `DataFrame` constructor from [DataFrames.jl](https://github.com/JuliaData/DataFrames.jl) has been extended to construct relevant data frames from lists of atoms or residues:
 
-```julia
+```julia-repl
 julia> using DataFrames
 
 julia> df = DataFrame(collectatoms(struc));
@@ -547,7 +641,7 @@ As with file writing disordered entities are expanded by default but this can be
 You can read and write files containing multiple mmCIF data blocks (equivalent to a `MMCIFDict` in this package) with the [`readmultimmcif`](@ref) and [`writemultimmcif`](@ref) functions.
 An example of such a file is the PDB's [chemical component dictionary](https://www.wwpdb.org/data/ccd).
 
-```julia
+```julia-repl
 julia> ccd = readmultimmcif("components.cif.gz"; gzip=true);
 
 julia> ccd["2W4"]
@@ -590,14 +684,14 @@ Multi-character chain IDs can be written to mmCIF and MMTF files but will throw
 If you want the PDB record line for an [`AbstractAtom`](@ref), use [`pdbline`](@ref).
 For example:
 
-```julia
+```julia-repl
 julia> pdbline(at)
 "HETATM  101  C  A  X B  20      10.500  20.123  -5.123  0.50 50.13           C1+"
 ```
 
 If you want to generate a PDB record line from values directly, do so using an [`AtomRecord`](@ref):
 
-```julia
+```julia-repl
 julia> pdbline(AtomRecord(false, 669, "CA", ' ', "ILE", "A", 90, ' ', [31.743, 33.11, 31.221], 1.00, 25.76, "C", ""))
 "ATOM    669  CA  ILE A  90      31.743  33.110  31.221  1.00 25.76           C  "
 ```

src/BioStructures.jl

@@ -31,6 +31,7 @@ include("mmcif.jl")
 include("mmtf.jl")
 include("spatial.jl")
 include("secondary.jl")
+include("select.jl")
 
 if !isdefined(Base, :get_extension)
     include("../ext/BioStructuresDataFramesExt.jl")