Make s prefix read current cell by default

lib/braingasm/compiler.rb

@@ -36,7 +36,9 @@ def zero
     end
 
     def signed
-      push_prefix ->(m) { m.last_write >= 0 ? 0 : 1 }
+      read_cell if @prefixes.empty?
+
+      push_prefix @prefixes.fix_params(->(n, m) { n < 0 ? 1 : 0 })
     end
 
     def parity

spec/compiler_spec.rb

@@ -228,29 +228,5 @@ module Braingasm
       end
     end
 
-    describe "#signed" do
-      before { allow(machine).to receive(:last_write).and_return(0) }
-      include_examples "generated prefix", :signed
-      include_examples "simple instruction generation", :signed, :last_write
-
-      it "returns 1 if machine's last write instruction is negative (signed)" do
-        expect(machine).to receive(:last_write).and_return(-1)
-
-        expect(subject.signed.call(machine)).to be 1
-      end
-
-      it "returns 0 if machine's last write instruction is 0 (unsigned)" do
-        expect(machine).to receive(:last_write).and_return(0)
-
-        expect(subject.signed.call(machine)).to be 0
-      end
-
-      it "returns 0 if machine's last write instruction is positive (unsigned)" do
-        expect(machine).to receive(:last_write).and_return(1)
-
-        expect(subject.signed.call(machine)).to be 0
-      end
-    end
-
   end
 end

spec/features/prefixes_spec.rb

@@ -51,11 +51,27 @@
 
   describe "s" do
     context "without prefix" do
-      it "returns 1 if the current cell is negative (signed), 0 otherwise"
+      it "returns 1 if the current cell is negative (signed), 0 otherwise" do
+        @machine.tape = [-2, -1, 0, 1, 2]
+
+        run "s, > s, > s, > s, > s,"
+
+        expect(@machine.tape).to be == [1, 1, 0, 0, 0]
+      end
     end
 
     context "with integer prefix" do
-      it "checks the prefix instead"
+      it "returns 0 if the given prefix is zero or positive" do
+        run "#s, > #s,"
+
+        expect(@machine.tape[0..1]).to be == [0, 0]
+      end
+
+      it "returns 1 if the given prefix is negative" do
+        run "< #s,"
+
+        expect(@machine.cell).to be == 1
+      end
     end
   end