branch: externals/parser-generator
commit 356372084758433e92baeb6537a6b3aff59dab64
Author: Christian Johansson <christ...@cvj.se>
Commit: Christian Johansson <christ...@cvj.se>
Updated docs about lexical analysis
---
docs/Lexical-Analysis.md | 92 +++++++++++++++++++++++++++++-------------------
1 file changed, 55 insertions(+), 37 deletions(-)
diff --git a/docs/Lexical-Analysis.md b/docs/Lexical-Analysis.md
index 45f4b8c..a356016 100644
--- a/docs/Lexical-Analysis.md
+++ b/docs/Lexical-Analysis.md
@@ -2,74 +2,92 @@
Set lexical analysis function by setting variable
`parser-generator-lex-analyzer--function`. Optionally set reset function by
setting variable `parser-generator-lex-analyzer--reset-function`. The lexical
analysis is indexed on variable `parser-generator-lex-analyzer--index`. All
parsers expect a list of tokens as response from lexical-analysis.
-### Peek next look-ahead
+## Token
-Returns the look-ahead number of next terminals in stream.
+A token is defined as a list with 3 elements, first is a string or symbol,
second is the start index of token in stream and third is the end index of
token in stream, second and third element have a dot between them, this
structure is to be compatible with Emacs Semantic system. Example token
+
+``` emacs-lisp
+'(("a" 1 . 2))
+```
+
+## Peek next look-ahead
+
+Returns the look-ahead number of next terminals in stream, if end of stream is
reached a EOF-identifier is returned.
``` emacs-lisp
(require 'ert)
(setq
parser-generator-lex-analyzer--function
- (lambda (index length)
- (let* ((string '(a a b b b))
+ (lambda (index)
+ (let* ((string '(("a" 1 . 2) ("b" 2 . 3) ("c" 3 . 4) ("d" 4 . 5)))
(string-length (length string))
- (max-index (+ index length))
- (tokens))
+ (max-index index)
+ (tokens)
+ (next-token))
(while (and
- (< index string-length)
- (< index max-index))
- (push (nth index string) tokens)
+ (< (1- index) string-length)
+ (< (1- index) max-index))
+ (setq next-token (nth (1- index) string))
+ (push next-token tokens)
(setq index (1+ index)))
(nreverse tokens))))
(parser-generator-lex-analyzer--reset)
(setq parser-generator--look-ahead-number 1)
- (should
- (equal
- '(a)
- (parser-generator-lex-analyzer--peek-next-look-ahead)))
+(setq parser-generator--look-ahead-number 1)
+(should
+ (equal
+ '(("a" 1 . 2))
+ (parser-generator-lex-analyzer--peek-next-look-ahead)))
- (setq parser-generator--look-ahead-number 2)
- (should
- (equal
- '(a b)
- (parser-generator-lex-analyzer--peek-next-look-ahead)))
+(setq parser-generator--look-ahead-number 2)
+(should
+ (equal
+ '(("a" 1 . 2) ("b" 2 . 3))
+ (parser-generator-lex-analyzer--peek-next-look-ahead)))
+(setq parser-generator--look-ahead-number 10)
+(should
+ (equal
+ '(("a" 1 . 2) ("b" 2 . 3) ("c" 3 . 4) ("d" 4 . 5) ($) ($) ($) ($) ($) ($))
+ (parser-generator-lex-analyzer--peek-next-look-ahead)))
```
-### Pop token
+## Pop token
-Returns the next token in stream and moves the index one point forward.
+Returns the next token in stream and moves the lexical analyzer index one
point forward. If end of stream is reached return nil.
``` emacs-lisp
(require 'ert)
(setq
parser-generator-lex-analyzer--function
- (lambda (index length)
- (let* ((string '(a b))
+ (lambda (index)
+ (let* ((string '(("a" 1 . 2) ("b" 2 . 3)))
(string-length (length string))
- (max-index (+ index length))
+ (max-index index)
(tokens))
(while (and
- (< index string-length)
- (< index max-index))
- (push (nth index string) tokens)
+ (< (1- index) string-length)
+ (< (1- index) max-index))
+ (push (nth (1- index) string) tokens)
(setq index (1+ index)))
(nreverse tokens))))
(parser-generator-lex-analyzer--reset)
+(setq parser-generator--look-ahead-number 1)
+
+(should
+ (equal
+ '(("a" 1 . 2))
+ (parser-generator-lex-analyzer--pop-token)))
+(should
+ (equal
+ '(("b" 2 . 3))
+ (parser-generator-lex-analyzer--pop-token)))
(should
- (equal
- '(a)
- (parser-generator-lex-analyzer--pop-token)))
- (should
- (equal
- '(b)
- (parser-generator-lex-analyzer--pop-token)))
- (should
- (equal
- nil
- (parser-generator-lex-analyzer--pop-token)))
+ (equal
+ nil
+ (parser-generator-lex-analyzer--pop-token)))
```
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