branch: externals/parser-generator
commit b756e1a6a25dce3a6711b0095e741f7db4d2d2c1
Author: Christian Johansson <[email protected]>
Commit: Christian Johansson <[email protected]>
Added example of parsing using LR algorithm
---
.../Deterministic-Right-Parser-for-LRk-Grammars.md | 50 ++++++++++++++++++++--
1 file changed, 47 insertions(+), 3 deletions(-)
diff --git a/docs/Deterministic-Right-Parser-for-LRk-Grammars.md
b/docs/Deterministic-Right-Parser-for-LRk-Grammars.md
index d449001..5ab9b02 100644
--- a/docs/Deterministic-Right-Parser-for-LRk-Grammars.md
+++ b/docs/Deterministic-Right-Parser-for-LRk-Grammars.md
@@ -16,12 +16,10 @@ Example with grammar with production: S -> SaSb and S is
non-terminal and a, b a
* B, C is parts of the production RHS, if the dot is the left B is nil and C
is the entire RHS. If the dot is at the right then B is the production RHS and
C is nil, otherwise B and C contains parts of the RHS
* L is the terminal look-ahead
-### LR items for prefix (S)
+## LR items for prefix (S)
Calculate the set of LR items valid for any viable prefix S.
-### Functions
-
``` emacs-lisp
(require 'ert)
@@ -54,4 +52,50 @@ Calculate the set of LR items valid for any viable prefix S.
(parser--lr-items-for-prefix 'S)))
```
+## Parse
+
+Perform a right-parse of input-stream.
+
+```emacs-lisp
+(require 'ert)
+
+(parser-generator--set-grammar '((Sp S) (a b) ((Sp S) (S (S a S b)) (S e)) Sp))
+(parser-generator--set-look-ahead-number 1)
+(parser-generator--process-grammar)
+(setq
+ parser-generator-lex-analyzer--function
+ (lambda (index length)
+ (let* ((string '(a a b b b))
+ (string-length (length string))
+ (max-index (+ index length))
+ (tokens))
+ (while (and
+ (< index string-length)
+ (< index max-index))
+ (push (nth index string) tokens)
+ (setq index (1+ index)))
+ (nreverse tokens))))
+(should
+ (equal
+ '(2 2 2 1 1)
+ (parser-generator-lr--parse)))
+
+
+(setq
+ parser-generator-lex-analyzer--function
+ (lambda (index length)
+ (let* ((string '(a a b b b))
+ (string-length (length string))
+ (max-index (+ index length))
+ (tokens))
+ (while (and
+ (< index string-length)
+ (< index max-index))
+ (push (nth index string) tokens)
+ (setq index (1+ index)))
+ (nreverse tokens))))
+(should-error
+ (parser-generator-lr--parse))
+```
+
[Back to start](../../../)
