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spec: var x = 'a' defaults to type rune

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R=gri, r, r, adg, iant, ken
CC=golang-dev
https://golang.org/cl/5444053
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Russ Cox 2011-12-08 21:48:19 -05:00
parent 136c04f71a
commit a933635579
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doc/go_spec.html
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@ -1,5 +1,5 @@
<!-- title The Go Programming Language Specification -->
<!-- subtitle Version of December 5, 2011 -->
<!-- subtitle Version of December 8, 2011 -->
<!--
TODO
@ -361,7 +361,7 @@ imaginary_lit = (decimals | float_lit) "i" .
<h3 id="Character_literals">Character literals</h3>
<p>
A character literal represents an <a href="#Constants">integer constant</a>,
A character literal represents a <a href="#Constants">character constant</a>,
typically a Unicode code point, as one or more characters enclosed in single
quotes. Within the quotes, any character may appear except single
quote and newline. A single quoted character represents itself,
@ -513,19 +513,22 @@ literal.
<h2 id="Constants">Constants</h2>
<p>There are <i>boolean constants</i>, <i>integer constants</i>,
<p>There are <i>boolean constants</i>,
<i>character constants</i>,
<i>integer constants</i>,
<i>floating-point constants</i>, <i>complex constants</i>,
and <i>string constants</i>. Integer, floating-point,
and <i>string constants</i>. Character, integer, floating-point,
and complex constants are
collectively called <i>numeric constants</i>.
</p>
<p>
A constant value is represented by an
A constant value is represented by a
<a href="#Character_literals">character</a>,
<a href="#Integer_literals">integer</a>,
<a href="#Floating-point_literals">floating-point</a>,
<a href="#Imaginary_literals">imaginary</a>,
<a href="#Character_literals">character</a>, or
or
<a href="#String_literals">string</a> literal,
an identifier denoting a constant,
a <a href="#Constant_expressions">constant expression</a>,
@ -3412,14 +3415,12 @@ operands and are evaluated at compile-time.
<p>
Untyped boolean, numeric, and string constants may be used as operands
wherever it is legal to use an operand of boolean, numeric, or string type,
respectively. Except for shift operations, if the operands of a binary operation
are an untyped integer constant and an untyped floating-point constant,
the integer constant is converted to an untyped floating-point constant
(relevant for <code>/</code> and <code>%</code>).
Similarly, untyped integer or floating-point constants may be used as operands
wherever it is legal to use an operand of complex type;
the integer or floating point constant is converted to a
complex constant with a zero imaginary part.
respectively.
Except for shift operations, if the operands of a binary operation are
different kinds of untyped constants, the operation and result use
the kind that appears later in this list: integer, character, floating-point, complex.
For example, an untyped integer constant divided by an
untyped complex constant yields an untyped complex constant.
</p>
<p>
@ -3435,32 +3436,30 @@ complex, or string constant).
</p>
<pre>
const a = 2 + 3.0 // a == 5.0 (floating-point constant)
const b = 15 / 4 // b == 3 (integer constant)
const c = 15 / 4.0 // c == 3.75 (floating-point constant)
const d = 1 &lt;&lt; 3.0 // d == 8 (integer constant)
const e = 1.0 &lt;&lt; 3 // e == 8 (integer constant)
const a = 2 + 3.0 // a == 5.0 (untyped floating-point constant)
const b = 15 / 4 // b == 3 (untyped integer constant)
const c = 15 / 4.0 // c == 3.75 (untyped floating-point constant)
const Θ float64 = 3/2 // Θ == 1.5 (type float64)
const d = 1 &lt;&lt; 3.0 // d == 8 (untyped integer constant)
const e = 1.0 &lt;&lt; 3 // e == 8 (untyped integer constant)
const f = int32(1) &lt;&lt; 33 // f == 0 (type int32)
const g = float64(2) &gt;&gt; 1 // illegal (float64(2) is a typed floating-point constant)
const h = "foo" &gt; "bar" // h == true (type bool)
const j = 'w' + 1 // j == 'x' (untyped character constant)
const Σ = 1 - 0.707 // (untyped complex constant)
const Δ = Σ + 2.0e-4 // (untyped complex constant)
const Φ = iota*1i - 1/1i // (untyped complex constant)
</pre>
<p>
Imaginary literals are untyped complex constants (with zero real part)
and may be combined in binary
operations with untyped integer and floating-point constants; the
result is an untyped complex constant.
Complex constants are always constructed from
constant expressions involving imaginary
literals or constants derived from them, or calls of the built-in function
<a href="#Complex_numbers"><code>complex</code></a>.
Applying the built-in function <code>complex</code> to untyped
integer, character, or floating-point constants yields
an untyped complex constant.
</p>
<pre>
const Σ = 1 - 0.707i
const Δ = Σ + 2.0e-4 - 1/1i
const Φ = iota * 1i
const iΓ = complex(0, Γ)
const ic = complex(0, c) // iΓ == 3.75i (untyped complex constant)
const iΘ = complex(0, Θ) // iΘ == 1.5i (type complex128)
</pre>
<p>
@ -3758,10 +3757,10 @@ In assignments, each value must be
<a href="#Assignability">assignable</a> to the type of the
operand to which it is assigned. If an untyped <a href="#Constants">constant</a>
is assigned to a variable of interface type, the constant is <a href="#Conversions">converted</a>
to type <code>bool</code>, <code>int</code>, <code>float64</code>,
to type <code>bool</code>, <code>rune</code>, <code>int</code>, <code>float64</code>,
<code>complex128</code> or <code>string</code>
respectively, depending on whether the value is a boolean, integer, floating-point,
complex, or string constant.
respectively, depending on whether the value is a boolean,
character, integer, floating-point, complex, or string constant.
</p>