From a10b4cff91cb5d26e2049f6efc20349aa4d50d20 Mon Sep 17 00:00:00 2001 From: Robert Griesemer Date: Tue, 5 Feb 2019 14:33:24 -0800 Subject: [PATCH] spec: document signed integer shift counts Updates #19113. Change-Id: I4726f51c5061c33979cdd061f6d4616fa97edb9a Reviewed-on: https://go-review.googlesource.com/c/161201 Reviewed-by: Rob Pike --- doc/go_spec.html | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/doc/go_spec.html b/doc/go_spec.html index dcc81ed628..f3d2320d86 100644 --- a/doc/go_spec.html +++ b/doc/go_spec.html @@ -1,6 +1,6 @@ @@ -3439,7 +3439,7 @@ to the type of the other operand.

-The right operand in a shift expression must have unsigned integer type +The right operand in a shift expression must have integer type or be an untyped constant representable by a value of type uint. If the left operand of a non-constant shift expression is an untyped constant, @@ -3586,7 +3586,9 @@ be replaced by a bitwise AND operation:

The shift operators shift the left operand by the shift count specified by the -right operand. They implement arithmetic shifts if the left operand is a signed +right operand, which must be positive. If the shift count is negative at run time, +a run-time panic occurs. +The shift operators implement arithmetic shifts if the left operand is a signed integer and logical shifts if it is an unsigned integer. There is no upper limit on the shift count. Shifts behave as if the left operand is shifted n times by 1 for a shift @@ -5921,7 +5923,7 @@ var a = complex(2, -2) // complex128 const b = complex(1.0, -1.4) // untyped complex constant 1 - 1.4i x := float32(math.Cos(math.Pi/2)) // float32 var c64 = complex(5, -x) // complex64 -var s uint = complex(1, 0) // untyped complex constant 1 + 0i can be converted to uint +var s int = complex(1, 0) // untyped complex constant 1 + 0i can be converted to int _ = complex(1, 2<<s) // illegal: 2 assumes floating-point type, cannot shift var rl = real(c64) // float32 var im = imag(a) // float64 -- 2.50.0