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add simple text about & and *.
clean up html: PLEASE RUN TIDY WHEN YOU EDIT THIS DOCUMENT deferring method value update until we decide what happens. R=gri DELTA=50 (38 added, 4 deleted, 8 changed) OCL=26609 CL=26612
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@ -22,7 +22,6 @@ Todo's:
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[ ] need to talk about precise int/floats clearly
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[ ] need to talk about precise int/floats clearly
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[ ] iant suggests to use abstract/precise int for len(), cap() - good idea
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[ ] iant suggests to use abstract/precise int for len(), cap() - good idea
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(issue: what happens in len() + const - what is the type?)
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(issue: what happens in len() + const - what is the type?)
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[ ] cleanup convert() vs T() vs x.(T) - convert() should go away?
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[ ] fix "else" part of if statement
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[ ] fix "else" part of if statement
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[ ] cleanup: 6g allows: interface { f F } where F is a function type.
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[ ] cleanup: 6g allows: interface { f F } where F is a function type.
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fine, but then we should also allow: func f F {}, where F is a function type.
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fine, but then we should also allow: func f F {}, where F is a function type.
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@ -124,6 +123,7 @@ Closed:
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and if so, does a label followed by an empty statement (a semicolon) still denote
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and if so, does a label followed by an empty statement (a semicolon) still denote
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a for loop that is following, and can break L be used inside it?
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a for loop that is following, and can break L be used inside it?
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[x] there is some funniness regarding ';' and empty statements and label decls
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[x] there is some funniness regarding ';' and empty statements and label decls
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[x] cleanup convert() vs T() vs x.(T) - convert() should go away?
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-->
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-->
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@ -1403,7 +1403,6 @@ Constants:
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Functions:
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Functions:
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cap len make new panic panicln print println
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cap len make new panic panicln print println
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(TODO: typeof??)
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Packages:
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Packages:
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sys (TODO: does sys endure?)
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sys (TODO: does sys endure?)
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@ -2664,17 +2663,30 @@ The right operand is evaluated conditionally.
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<h3>Address operators</h3>
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<h3>Address operators</h3>
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<!--TODO(r): This section is a mess. Skipping it for now.-->
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<p>
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<p>
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<font color=red>TODO: Need to talk about unary "*", clean up section below.</font>
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The unary prefix address-of operator <code>&</code> generates the address of its operand, which must be a variable,
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pointer indirection, field selector, or array or slice indexing operation. It is illegal to take the address of a function
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result variable.
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Given an operand of pointer type, the unary prefix pointer indirection operator <code>*</code> retrieves the value pointed
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to by the operand.
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</p>
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<pre>
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&x
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&a[f(2)]
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*p
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*pf(x)
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</pre>
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<p>
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<p>
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<font color=red>TODO: This text needs to be cleaned up and go elsewhere, there are no address
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<font color=red>TODO: This text needs to be cleaned up and go elsewhere, there are no address
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operators involved.
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operators involved.
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</font>
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</font>
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</p>
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<p>
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<p>
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Methods are a form of function, and a method ``value'' has a function type.
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Methods are a form of function and a method ``value'' has a function type.
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Consider the type T with method M:
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Consider the type T with method M:
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</p>
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<pre>
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<pre>
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type T struct {
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type T struct {
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@ -2684,25 +2696,33 @@ func (tp *T) M(a int) int;
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var t *T;
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var t *T;
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</pre>
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</pre>
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<p>
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To construct the value of method M, one writes
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To construct the value of method M, one writes
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</p>
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<pre>
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<pre>
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t.M
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t.M
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</pre>
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</pre>
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<p>
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using the variable t (not the type T).
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using the variable t (not the type T).
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<font color=red>TODO: It makes perfect sense to be able to say T.M (in fact, it makes more
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<font color=red>TODO: It makes perfect sense to be able to say T.M (in fact, it makes more
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sense then t.M, since only the type T is needed to find the method M, i.e.,
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sense then t.M, since only the type T is needed to find the method M, i.e.,
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its address). TBD.
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its address). TBD.
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</font>
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</font>
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</p>
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<p>
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The expression t.M is a function value with type
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The expression t.M is a function value with type
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</p>
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<pre>
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<pre>
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func (t *T, a int) int
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func (t *T, a int) int
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</pre>
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</pre>
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<p>
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and may be invoked only as a function, not as a method:
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and may be invoked only as a function, not as a method:
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</p>
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<pre>
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<pre>
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var f func (t *T, a int) int;
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var f func (t *T, a int) int;
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@ -2710,30 +2730,39 @@ f = t.M;
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x := f(t, 7);
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x := f(t, 7);
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</pre>
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</pre>
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<p>
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Note that one does not write t.f(7); taking the value of a method demotes
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Note that one does not write t.f(7); taking the value of a method demotes
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it to a function.
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it to a function.
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</p>
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<p>
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In general, given type T with method M and variable t of type T,
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In general, given type T with method M and variable t of type T,
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the method invocation
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the method invocation
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</p>
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<pre>
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<pre>
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t.M(args)
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t.M(args)
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</pre>
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</pre>
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<p>
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is equivalent to the function call
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is equivalent to the function call
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</p>
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<pre>
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<pre>
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(t.M)(t, args)
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(t.M)(t, args)
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</pre>
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</pre>
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<p>
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<font color=red>
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<font color=red>
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TODO: should probably describe the effect of (t.m) under §Expressions if t.m
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TODO: should probably describe the effect of (t.m) under §Expressions if t.m
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denotes a method: Effect is as described above, converts into function.
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denotes a method: Effect is as described above, converts into function.
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</font>
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</font>
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</p>
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<p>
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<p>
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If T is an interface type, the expression t.M does not determine which
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If T is an interface type, the expression t.M does not determine which
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underlying type's M is called until the point of the call itself. Thus given
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underlying type's M is called until the point of the call itself. Thus given
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T1 and T2, both implementing interface I with method M, the sequence
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T1 and T2, both implementing interface I with method M, the sequence
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</p>
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<pre>
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<pre>
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var t1 *T1;
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var t1 *T1;
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@ -2743,8 +2772,10 @@ m := i.M;
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m(t2, 7);
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m(t2, 7);
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</pre>
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</pre>
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<p>
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will invoke t2.M() even though m was constructed with an expression involving
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will invoke t2.M() even though m was constructed with an expression involving
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t1. Effectively, the value of m is a function literal
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t1. Effectively, the value of m is a function literal
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</p>
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<pre>
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<pre>
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func (recv I, a int) {
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func (recv I, a int) {
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@ -2752,13 +2783,16 @@ func (recv I, a int) {
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}
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}
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</pre>
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</pre>
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<p>
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that is automatically created.
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that is automatically created.
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</p>
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<p>
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<p>
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<font color=red>
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<font color=red>
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TODO: Document implementation restriction: It is illegal to take the address
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TODO: Document implementation restriction: It is illegal to take the address
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of a result parameter (e.g.: func f() (x int, p *int) { return 2, &x }).
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of a result parameter (e.g.: func f() (x int, p *int) { return 2, &x }).
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(TBD: is it an implementation restriction or fact?)
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(TBD: is it an implementation restriction or fact?)
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</font>
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</font>
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</p>
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<h3>Communication operators</h3>
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<h3>Communication operators</h3>
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@ -3131,11 +3165,13 @@ if x := f(); x < y {
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An expression or type specifier is compared to the "cases"
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An expression or type specifier is compared to the "cases"
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inside the "switch" to determine which branch
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inside the "switch" to determine which branch
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to execute.
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to execute.
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</p>
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<pre class="grammar">
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<pre class="grammar">
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SwitchStat = ExprSwitchStat | TypeSwitchStat .
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SwitchStat = ExprSwitchStat | TypeSwitchStat .
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</pre>
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</pre>
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<p>
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There are two forms: expression switches and type switches.
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There are two forms: expression switches and type switches.
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In an expression switch, the cases contain expressions that are compared
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In an expression switch, the cases contain expressions that are compared
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against the value of the switch expression.
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against the value of the switch expression.
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@ -3690,7 +3726,6 @@ for i := 0; i <= 3; i++ {
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<h2>Predeclared functions</h2>
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<h2>Predeclared functions</h2>
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<ul>
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<ul>
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<li>cap
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<li>cap
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<li>convert
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<li>len
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<li>len
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<li>make
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<li>make
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<li>new
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<li>new
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@ -3698,7 +3733,6 @@ for i := 0; i <= 3; i++ {
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<li>panicln
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<li>panicln
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<li>print
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<li>print
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<li>println
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<li>println
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<li>typeof
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</ul>
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</ul>
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<h3>Length and capacity</h3>
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<h3>Length and capacity</h3>
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