Add generic y-only overload for stairs!

Author: kojix2

spec/unicode_plot_spec.cr

@@ -390,6 +390,13 @@ describe UnicodePlot do
       p.to_s.should be_a(String)
     end
 
+    it "accepts y-only numeric overload in stairs!" do
+      p = UnicodePlot.stairs([1, 2, 3], [4, 5, 6])
+      prev_series = p.series
+      UnicodePlot.stairs!(p, [7, 8, 9])
+      p.series.should eq(prev_series + 1)
+    end
+
     it "accepts UInt128 arrays via generic numeric overload" do
       p = UnicodePlot.stairs([1_u128, 2_u128, 3_u128], [4_u128, 5_u128, 6_u128])
       p.to_s.should be_a(String)

src/unicode_plot/interface/stairs.cr

@@ -105,4 +105,14 @@ module UnicodePlot
   def stairs!(plot : Plot, x : Array(T), y : Array(U), **kwargs) : Plot forall T, U
     stairs!(plot, to_plot_f64(x), to_plot_f64(y), **kwargs)
   end
+
+  def stairs!(plot : Plot, y : Array(Float64), **kwargs) : Plot
+    x = (1..y.size).map(&.to_f64)
+    stairs!(plot, x, y, **kwargs)
+  end
+
+  def stairs!(plot : Plot, y : Array(T), **kwargs) : Plot forall T
+    x = (1..y.size).map(&.to_f64)
+    stairs!(plot, x, to_plot_f64(y), **kwargs)
+  end
 end