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Diffstat (limited to 'doc/manual.md')
| -rw-r--r-- | doc/manual.md | 62 |
1 files changed, 54 insertions, 8 deletions
diff --git a/doc/manual.md b/doc/manual.md index 3b402e9f4..5c36a0a7b 100644 --- a/doc/manual.md +++ b/doc/manual.md @@ -3220,6 +3220,15 @@ A const section declares constants whose values are constant expressions: Once declared, a constant's symbol can be used as a constant expression. +The value part of a constant declaration opens a new scope for each constant, +so no symbols declared in the constant value are accessible outside of it. + + ```nim + const foo = (var a = 1; a) + const bar = a # error + let baz = a # error + ``` + See [Constants and Constant Expressions] for details. Static statement/expression @@ -3788,9 +3797,6 @@ type conversions to unsigned integers and between unsigned integers. The rationale for this is mostly better interoperability with the C Programming language when algorithms are ported from C to Nim. -Exception: Values that are converted to an unsigned type at compile time -are checked so that code like `byte(-1)` does not compile. - **Note**: Historically the operations were unchecked and the conversions were sometimes checked but starting with the revision 1.0.4 of this document and the language implementation the @@ -4457,7 +4463,42 @@ as an example: Overloading of the subscript operator ------------------------------------- -The `[]` subscript operator for arrays/openarrays/sequences can be overloaded. +The `[]` subscript operator for arrays/openarrays/sequences can be overloaded +for any type (with some exceptions) by defining a routine with the name `[]`. + + ```nim + type Foo = object + data: seq[int] + + proc `[]`(foo: Foo, i: int): int = + result = foo.data[i] + + let foo = Foo(data: @[1, 2, 3]) + echo foo[1] # 2 + ``` + +Assignment to subscripts can also be overloaded by naming a routine `[]=`, +which has precedence over assigning to the result of `[]`. + + ```nim + type Foo = object + data: seq[int] + + proc `[]`(foo: Foo, i: int): int = + result = foo.data[i] + proc `[]=`(foo: var Foo, i: int, val: int) = + foo.data[i] = val + + var foo = Foo(data: @[1, 2, 3]) + echo foo[1] # 2 + foo[1] = 5 + echo foo.data # @[1, 5, 3] + echo foo[1] # 5 + ``` + +Overloads of the subscript operator cannot be applied to routine or type +symbols themselves, as this conflicts with the syntax for instantiating +generic parameters, i.e. `foo[int](1, 2, 3)` or `Foo[int]`. Methods @@ -5419,6 +5460,8 @@ To override the compiler's side effect analysis a `{.noSideEffect.}` **Side effects are usually inferred. The inference for side effects is analogous to the inference for exception tracking.** +When the compiler cannot infer side effects, as is the case for imported +functions, one can annotate them with the `sideEffect` pragma. GC safety effect ---------------- @@ -6214,9 +6257,12 @@ scope is controlled by the `inject`:idx: and `gensym`:idx: pragmas: `gensym`'ed symbols are not exposed but `inject`'ed symbols are. The default for symbols of entity `type`, `var`, `let` and `const` -is `gensym` and for `proc`, `iterator`, `converter`, `template`, -`macro` is `inject`. However, if the name of the entity is passed as a -template parameter, it is an `inject`'ed symbol: +is `gensym`. For `proc`, `iterator`, `converter`, `template`, +`macro`, the default is `inject`, but if a `gensym` symbol with the same name +is defined in the same syntax-level scope, it will be `gensym` by default. +This can be overriden by marking the routine as `inject`. + +If the name of the entity is passed as a template parameter, it is an `inject`'ed symbol: ```nim template withFile(f, fn, mode: untyped, actions: untyped): untyped = @@ -8701,7 +8747,7 @@ after the last specified parameter. Nim string values will be converted to C strings automatically: ```Nim - proc printf(formatstr: cstring) {.nodecl, varargs.} + proc printf(formatstr: cstring) {.header: "<stdio.h>", varargs.} printf("hallo %s", "world") # "world" will be passed as C string ``` |