Support comprehensions

README.md

@@ -20,7 +20,7 @@ FizzBuzz
 
 def fizzbuzz(n):
     # this is still Julia, even though it looks like Python!
-    # so range includes both endpoints
+    # so range includes 1 and has length n — very different from Python.
     for i in range(1, n):
         if i % 15 == 0:
             println("FizzBuzz")

src/PythonSyntax.jl

@@ -68,8 +68,12 @@ function transpile(t::PyObject)
         ast.Dict => :(Dict(zip($(transpile(:vect, t[:keys])),
                 $(transpile(:vect, t[:values])))))
         ast.Set => :(Set($(transpile(:vect, t[:elts]))))
-        ast.ListComp || ast.SetComp || ast.DictComp || ast.GeneratorExp =>
-            error("Comprehensions are not yet supported.")
+        ast.ListComp => transpilecomp(t)
+        ast.SetComp => :(Set($(transpilecomp(t))))
+        ast.DictComp =>
+            error("Dictionary comprehensions are not yet supported.")
+        ast.GeneratorExp =>
+            error("Generators are not yet supported.")
         ast.Await || ast.Yield || ast.YieldFrom =>
             error("Generators are not yet supported.")
         ast.Compare => transpilecmp(t)

src/expr.jl

@@ -1,3 +1,16 @@
+function transpilegen(gen)
+    if !isempty(gen[:ifs])
+        throw(ArgumentError("conditionals not supported in comprehensions"))
+    end
+    Expr(:(=), transpile(gen[:target]), transpile(gen[:iter]))
+end
+
+function transpilecomp(comp)
+    Expr(:comprehension,
+            transpile(comp[:elt]),
+            transpilegen.(comp[:generators])...)
+end
+
 function transpileassign(t)
     targets = transpile.(t[:targets])
     lhs = if length(targets) == 1

test/arrays.jl

@@ -0,0 +1,7 @@
+@testset "Arrays" begin
+
+@test pysyntax"[1, 2, 3]" == [1, 2, 3]
+@test pysyntax"[i for i in range(1, 10)]" == collect(1:10)
+@test pysyntax"{i**2 for i in range(-5, 11)}" == Set([0, 1, 4, 9, 16, 25])
+
+end  # testset

test/magic.jl

@@ -0,0 +1,23 @@
+@testset "Magic" begin
+
+@test pysyntax"""
+def goto():
+    __mc__(goto, skip)
+    return False
+    __mc__(label, skip)
+    return True
+
+goto()
+"""
+
+@test pysyntax"""
+def goto():
+    __jl__("@goto skip")
+    return False
+    __jl__("@label skip")
+    return True
+
+goto()
+"""
+
+end  # testset

test/runtests.jl

@@ -6,4 +6,6 @@ include("control.jl")
 include("io.jl")
 include("functions.jl")
 include("classes.jl")
+include("magic.jl")
+include("arrays.jl")
 include("stl.jl")