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-rw-r--r--third_party/python/ply/example/BASIC/basiclex.py61
1 files changed, 61 insertions, 0 deletions
diff --git a/third_party/python/ply/example/BASIC/basiclex.py b/third_party/python/ply/example/BASIC/basiclex.py
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index 0000000000..4151f4c34f
--- /dev/null
+++ b/third_party/python/ply/example/BASIC/basiclex.py
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+# An implementation of Dartmouth BASIC (1964)
+
+from ply import *
+
+keywords = (
+ 'LET', 'READ', 'DATA', 'PRINT', 'GOTO', 'IF', 'THEN', 'FOR', 'NEXT', 'TO', 'STEP',
+ 'END', 'STOP', 'DEF', 'GOSUB', 'DIM', 'REM', 'RETURN', 'RUN', 'LIST', 'NEW',
+)
+
+tokens = keywords + (
+ 'EQUALS', 'PLUS', 'MINUS', 'TIMES', 'DIVIDE', 'POWER',
+ 'LPAREN', 'RPAREN', 'LT', 'LE', 'GT', 'GE', 'NE',
+ 'COMMA', 'SEMI', 'INTEGER', 'FLOAT', 'STRING',
+ 'ID', 'NEWLINE'
+)
+
+t_ignore = ' \t'
+
+
+def t_REM(t):
+ r'REM .*'
+ return t
+
+
+def t_ID(t):
+ r'[A-Z][A-Z0-9]*'
+ if t.value in keywords:
+ t.type = t.value
+ return t
+
+t_EQUALS = r'='
+t_PLUS = r'\+'
+t_MINUS = r'-'
+t_TIMES = r'\*'
+t_POWER = r'\^'
+t_DIVIDE = r'/'
+t_LPAREN = r'\('
+t_RPAREN = r'\)'
+t_LT = r'<'
+t_LE = r'<='
+t_GT = r'>'
+t_GE = r'>='
+t_NE = r'<>'
+t_COMMA = r'\,'
+t_SEMI = r';'
+t_INTEGER = r'\d+'
+t_FLOAT = r'((\d*\.\d+)(E[\+-]?\d+)?|([1-9]\d*E[\+-]?\d+))'
+t_STRING = r'\".*?\"'
+
+
+def t_NEWLINE(t):
+ r'\n'
+ t.lexer.lineno += 1
+ return t
+
+
+def t_error(t):
+ print("Illegal character %s" % t.value[0])
+ t.lexer.skip(1)
+
+lex.lex(debug=0)