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zevv / npeg

PEGs for Nim, another take
MIT License
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mixin repr in dumpSubject #30

Closed liquidev closed 3 years ago

liquidev commented 3 years ago

This is to allow the user to override the repr in npegTrace with their own version. system.repr completely blows the trace up when the user uses a type that's not trivial (such as an object). For instance, the following type:

  TokenKind* = enum
    tkNumber = "number"
    tkIdent = "ident"

  Token* = object
    line*: int
    case kind*: TokenKind
    of tkNumber: number*: float
    of tkIdent: ident*: string

Results in traces looking like this:

 12|  0|  6|[line = 1,
{]           |call           |  capopen ckAction -> 6                 |**
 13|  0|  6|[line = 1,
{]           |callOp         |   capopen ckAction -> 6                |**
 14|  0|  6|[line = 1,
{]           |callOp         |    lit :                               |**
180|  0|  6|[line = 1,
{]           |               |opFail (backtrack)                      |**
 27|  0|  6|[line = 1,
{]           |show           | capopen ckAction -> 6                  |*
 28|  0|  6|[line = 1,
{]           |show           |  capopen ckVal -> 6                    |*
 29|  0|  6|[line = 1,
{]           |show           |   choice 32                            |*
 30|  0|  6|[line = 1,
{]           |show           |    lit !                               |**

due to system.repr inserting newlines wherever it wants. This PR allows the user to declare their own repr, like so:

proc repr(t: Token) = $t.kind  # or something. the user decides!