diff options
Diffstat (limited to 'doc/pegdocs.txt')
| -rw-r--r-- | doc/pegdocs.txt | 60 |
1 files changed, 30 insertions, 30 deletions
diff --git a/doc/pegdocs.txt b/doc/pegdocs.txt index 118949cad..4c557aed8 100644 --- a/doc/pegdocs.txt +++ b/doc/pegdocs.txt @@ -14,7 +14,7 @@ notation meaning order, to the text ahead, until one of them succeeds and possibly consumes some text. Indicate success if one of expressions succeeded. Otherwise do not consume any text - and indicate failure. + and indicate failure. ``A ... Z`` Sequence: Apply expressions `A`, ..., `Z`, in this order, to consume consecutive portions of the text ahead, as long as they succeed. Indicate success if all succeeded. @@ -27,11 +27,11 @@ notation meaning ``{E}`` Capture: Apply expression `E` and store the substring that matched `E` into a *capture* that can be accessed after the matching process. -``$i`` Back reference to the ``i``th capture. ``i`` counts from 1. -``$`` Anchor: Matches at the end of the input. No character - is consumed. Same as ``!.``. -``^`` Anchor: Matches at the start of the input. No character - is consumed. +``$i`` Back reference to the ``i``th capture. ``i`` counts from 1. +``$`` Anchor: Matches at the end of the input. No character + is consumed. Same as ``!.``. +``^`` Anchor: Matches at the start of the input. No character + is consumed. ``&E`` And predicate: Indicate success if expression `E` matches the text ahead; otherwise indicate failure. Do not consume any text. @@ -41,15 +41,15 @@ notation meaning ``E+`` One or more: Apply expression `E` repeatedly to match the text ahead, as long as it succeeds. Consume the matched text (if any) and indicate success if there was at least - one match. Otherwise indicate failure. + one match. Otherwise indicate failure. ``E*`` Zero or more: Apply expression `E` repeatedly to match the text ahead, as long as it succeeds. Consume the matched - text (if any). Always indicate success. + text (if any). Always indicate success. ``E?`` Zero or one: If expression `E` matches the text ahead, - consume it. Always indicate success. + consume it. Always indicate success. ``[s]`` Character class: If the character ahead appears in the string `s`, consume it and indicate success. Otherwise - indicate failure. + indicate failure. ``[a-b]`` Character range: If the character ahead is one from the range `a` through `b`, consume it and indicate success. Otherwise indicate failure. @@ -70,7 +70,7 @@ notation meaning failure. ``@E`` Search: Shorthand for ``(!E .)* E``. (Search loop for the pattern `E`.) -``{@} E`` Captured Search: Shorthand for ``{(!E .)*} E``. (Search +``{@} E`` Captured Search: Shorthand for ``{(!E .)*} E``. (Search loop for the pattern `E`.) Everything until and exluding `E` is captured. ``@@ E`` Same as ``{@} E``. @@ -79,7 +79,7 @@ notation meaning matching engine.** ``\identifier`` Built-in macro for a longer expression. ``\ddd`` Character with decimal code *ddd*. -``\"``, etc Literal ``"``, etc. +``\"``, etc Literal ``"``, etc. =============== ============================================================ @@ -101,9 +101,9 @@ macro meaning ``\n`` any newline combination: ``\10 / \13\10 / \13`` ``\i`` ignore case for matching; use this at the start of the PEG ``\y`` ignore style for matching; use this at the start of the PEG -``\skip`` pat skip pattern *pat* before trying to match other tokens; +``\skip`` pat skip pattern *pat* before trying to match other tokens; this is useful for whitespace skipping, for example: - ``\skip(\s*) {\ident} ':' {\ident}`` matches key value + ``\skip(\s*) {\ident} ':' {\ident}`` matches key value pairs ignoring whitespace around the ``':'``. ``\ident`` a standard ASCII identifier: ``[a-zA-Z_][a-zA-Z_0-9]*`` ``\letter`` any Unicode letter @@ -133,42 +133,42 @@ The PEG parser implements this grammar (written in PEG syntax):: # Example grammar of PEG in PEG syntax. # Comments start with '#'. # First symbol is the start symbol. - + grammar <- rule* / expr - + identifier <- [A-Za-z][A-Za-z0-9_]* charsetchar <- "\\" . / [^\]] charset <- "[" "^"? (charsetchar ("-" charsetchar)?)+ "]" stringlit <- identifier? ("\"" ("\\" . / [^"])* "\"" / "'" ("\\" . / [^'])* "'") builtin <- "\\" identifier / [^\13\10] - + comment <- '#' @ \n ig <- (\s / comment)* # things to ignore - + rule <- identifier \s* "<-" expr ig identNoArrow <- identifier !(\s* "<-") prefixOpr <- ig '&' / ig '!' / ig '@' / ig '{@}' / ig '@@' literal <- ig identifier? '$' [0-9]+ / '$' / '^' / - ig identNoArrow / - ig charset / - ig stringlit / - ig builtin / - ig '.' / - ig '_' / + ig identNoArrow / + ig charset / + ig stringlit / + ig builtin / + ig '.' / + ig '_' / (ig "(" expr ig ")") postfixOpr <- ig '?' / ig '*' / ig '+' primary <- prefixOpr* (literal postfixOpr*) - + # Concatenation has higher priority than choice: # ``a b / c`` means ``(a b) / c`` - + seqExpr <- primary+ expr <- seqExpr (ig "/" expr)* -**Note**: As a special syntactic extension if the whole PEG is only a single -expression, identifiers are not interpreted as non-terminals, but are +**Note**: As a special syntactic extension if the whole PEG is only a single +expression, identifiers are not interpreted as non-terminals, but are interpreted as verbatim string: .. code-block:: nim @@ -185,10 +185,10 @@ Check if `s` matches Nim's "while" keyword: .. code-block:: nim s =~ peg" y'while'" -Exchange (key, val)-pairs: +Exchange (key, val)-pairs: .. code-block:: nim - "key: val; key2: val2".replace(peg"{\ident} \s* ':' \s* {\ident}", "$2: $1") + "key: val; key2: val2".replacef(peg"{\ident} \s* ':' \s* {\ident}", "$2: $1") Determine the ``#include``'ed files of a C file: |