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[elpa] externals/parser-generator b756e1a 135/434: Added example of pars


From: ELPA Syncer
Subject: [elpa] externals/parser-generator b756e1a 135/434: Added example of parsing using LR algorithm
Date: Mon, 29 Nov 2021 15:59:26 -0500 (EST)

branch: externals/parser-generator
commit b756e1a6a25dce3a6711b0095e741f7db4d2d2c1
Author: Christian Johansson <christian@cvj.se>
Commit: Christian Johansson <christian@cvj.se>

    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](../../../)



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