From 7aed4587e568bf9a4f2e562623d63d13dc87209b Mon Sep 17 00:00:00 2001
From: Leandro Martinez <lmartine@unicamp.br>
Date: Tue, 11 Feb 2025 15:31:55 -0300
Subject: [PATCH] support interpolation in sel"" macro.

---
 src/select.jl    | 29 +++++++++++++++++++++++++----
 test/runtests.jl |  5 +++++
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/src/select.jl b/src/select.jl
index 504fbc8..9b3a7e8 100644
--- a/src/select.jl
+++ b/src/select.jl
@@ -435,18 +435,39 @@ Trivial selector that returns `true` for any structural element.
 allselector(el) = true
 
 # Acts as a function when used within typical julia filtering functions 
-#   by converting a string selection into a query call
+# by converting a string selection into a query call
 struct Select <: Function
     sel::String
 end
-
 (s::Select)(at) = apply_query(parse_query(s.sel), at)
 
+#
+# Parse selection string allowing interpolation in sel macro:
+# https://discourse.julialang.org/t/str-string-interpolation/125766/11?u=lmiq
+#
+_select(args...) = Select(string(args...))
 "String selection syntax."
-macro sel_str(str)
-    Select(str)
+macro sel_str(s)
+    ex = Expr(:call, GlobalRef(BioStructures, :_select))
+    i = firstindex(s)
+    buf = IOBuffer(maxsize=ncodeunits(s))
+    while i <= ncodeunits(s)
+        c = @inbounds s[i]
+        i = nextind(s, i)
+        if c === '$'
+            position(buf) > 0 && push!(ex.args, String(take!(buf)))
+            val, i = Meta.parse(s, i; greedy=false)
+            Meta.isexpr(val, :incomplete) && error(val.args[1])
+            val !== nothing && push!(ex.args, val)
+        else
+            print(buf, c)
+        end
+    end
+    position(buf) > 0 && push!(ex.args, String(take!(buf)))
+    return esc(ex)
 end
 
+
 const operators = (
     "="  => (x, y) -> isequal(x, y),
     "<"  => (x, y) -> isless(x, y),
diff --git a/test/runtests.jl b/test/runtests.jl
index 6838387..86603b4 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -928,6 +928,11 @@ end
     @test length(collectatoms(struc, sel"disordered")) == 68
     @test length(collectatoms(struc, sel"sscode E")) == 2448
     @test length(collectatoms(struc, sel"helix")) == 4047
+    # check interpolation support
+    ss_type = "helix"
+    @test length(collectatoms(struc, sel"$ss_type")) == 4047
+    sel_chains = ('A', 'B')
+    @test length(collectresidues(struc, sel"chain $(first(sel_chains)) or chain $(last(sel_chains))")) == 544
 
     @test length(collectresidues(struc, sel"chain A or chain B")) == 544
     @test length(collectresidues(struc, sel"standard")) == 1420