From e009628c091d2b108ec7fae4649bc97ea670eb65 Mon Sep 17 00:00:00 2001
From: Katharine Hyatt <67932820+kshyatt-aws@users.noreply.github.com>
Date: Fri, 27 Sep 2024 11:25:48 -0400
Subject: [PATCH] fix: Support casting for most types (#54)

---
 src/Quasar.jl          | 19 ++++++++++++++----
 test/test_openqasm3.jl | 44 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/src/Quasar.jl b/src/Quasar.jl
index 672f727..8019dbe 100644
--- a/src/Quasar.jl
+++ b/src/Quasar.jl
@@ -1769,10 +1769,21 @@ function (v::AbstractVisitor)(program_expr::QasmExpression)
         return evaluate_unary_op(op, arg)
     elseif head(program_expr) == :cast
         casting_to = program_expr.args[1].args[1]
-        value = v(program_expr.args[2])
-        if casting_to == Bool
-            return value > 0
-        # TODO
+        value      = v(program_expr.args[2])
+        if casting_to == Bool && !(value isa Period)
+            return value isa BitVector ? any(value) : value > 0
+        elseif casting_to isa SizedBitVector && !(value isa Period || value isa AbstractFloat)
+            new_size = v(casting_to.size)
+            return value isa BitVector ? value[1:new_size] : BitVector(reverse(digits(value, base=2, pad=new_size)))
+        elseif casting_to isa SizedNumber && !(value isa Period)
+            num_value = value isa BitVector ? sum(reverse(value)[k]*2^(k-1) for k=1:length(value)) : value
+            if casting_to isa SizedInt
+                return Int(num_value)
+            elseif casting_to isa SizedUInt
+                return UInt(num_value)
+            elseif casting_to isa SizedFloat
+                return Float64(num_value)
+            end
         else
             throw(QasmVisitorError("unable to evaluate cast expression $program_expr"))
         end
diff --git a/test/test_openqasm3.jl b/test/test_openqasm3.jl
index 5fffd09..4e02dbd 100644
--- a/test/test_openqasm3.jl
+++ b/test/test_openqasm3.jl
@@ -261,6 +261,50 @@ get_tol(shots::Int) = return (
         @test simulation.state_vector ≈ sv 
         @test circuit.result_types == [BraketSimulator.Amplitude(["00", "01", "10", "11"])]
     end
+    @testset "Casting" begin
+        @testset "Casting to $to_type from $from_type" for (to_type, to_value) in (("bool", true),), (from_type, from_value) in (("int[32]", "32",),
+                                                                                                                              ("uint[16]", "1",),
+                                                                                                                              ("float", "2.5",),
+                                                                                                                              ("bool", "true",),
+                                                                                                                              ("bit", "\"1\"",),
+                                                                                                                             )
+            qasm = """
+            $from_type a = $from_value;
+            $to_type b = $to_type(a);
+            """
+            parsed  = parse_qasm(qasm)
+            visitor = QasmProgramVisitor()
+            visitor(parsed)
+            @test visitor.classical_defs["b"].val == to_value
+        end
+        @testset "Casting to $to_type from $from_type" for (to_type, to_value) in (("uint[32]", 32), ("int[16]", 32), ("float", 32.0)), (from_type, from_value) in (("int[32]", "32",),
+                                                                                                                                                   ("uint[16]", "32",),
+                                                                                                                                                   ("float", "32.0",),
+                                                                                                                                                   ("bit[6]", "\"100000\"",),
+                                                                                                                                                  )
+            qasm = """
+            $from_type a = $from_value;
+            $to_type b = $to_type(a);
+            """
+            parsed  = parse_qasm(qasm)
+            visitor = QasmProgramVisitor()
+            visitor(parsed)
+            @test visitor.classical_defs["b"].val == to_value
+        end
+        @testset "Casting to $to_type from $from_type" for (to_type, to_value) in (("bit[6]", BitVector([1,0,0,0,0,0])),), (from_type, from_value) in (("int[32]", "32",),
+                                                                                                                                                   ("uint[16]", "32",),
+                                                                                                                                                   ("bit[6]", "\"100000\"",),
+                                                                                                                                                  )
+            qasm = """
+            $from_type a = $from_value;
+            $to_type b = $to_type(a);
+            """
+            parsed  = parse_qasm(qasm)
+            visitor = QasmProgramVisitor()
+            visitor(parsed)
+            @test visitor.classical_defs["b"].val == to_value
+        end
+    end
     @testset "Numbers $qasm_str" for (qasm_str, var_name, output_val) in (("float[32] a = 1.24e-3;", "a", 1.24e-3),
                                                                           ("complex[float] b = 1-0.23im;", "b", 1-0.23im),
                                                                           ("const bit c = \"0\";", "c", falses(1)),