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Diffstat (limited to 'test/pkg_test5/parsing/calcparse.py')
-rw-r--r-- | test/pkg_test5/parsing/calcparse.py | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/test/pkg_test5/parsing/calcparse.py b/test/pkg_test5/parsing/calcparse.py new file mode 100644 index 0000000..2a1ddfe --- /dev/null +++ b/test/pkg_test5/parsing/calcparse.py @@ -0,0 +1,67 @@ +# ----------------------------------------------------------------------------- +# yacc_simple.py +# +# A simple, properly specifier grammar +# ----------------------------------------------------------------------------- + +from .calclex import tokens +from ply import yacc + +# Parsing rules +precedence = ( + ('left','PLUS','MINUS'), + ('left','TIMES','DIVIDE'), + ('right','UMINUS'), + ) + +# dictionary of names +names = { } + +def p_statement_assign(t): + 'statement : NAME EQUALS expression' + names[t[1]] = t[3] + +def p_statement_expr(t): + 'statement : expression' + t[0] = t[1] + +def p_expression_binop(t): + '''expression : expression PLUS expression + | expression MINUS expression + | expression TIMES expression + | expression DIVIDE expression''' + if t[2] == '+' : t[0] = t[1] + t[3] + elif t[2] == '-': t[0] = t[1] - t[3] + elif t[2] == '*': t[0] = t[1] * t[3] + elif t[2] == '/': t[0] = t[1] / t[3] + +def p_expression_uminus(t): + 'expression : MINUS expression %prec UMINUS' + t[0] = -t[2] + +def p_expression_group(t): + 'expression : LPAREN expression RPAREN' + t[0] = t[2] + +def p_expression_number(t): + 'expression : NUMBER' + t[0] = t[1] + +def p_expression_name(t): + 'expression : NAME' + try: + t[0] = names[t[1]] + except LookupError: + print("Undefined name '%s'" % t[1]) + t[0] = 0 + +def p_error(t): + print("Syntax error at '%s'" % t.value) + +import os.path +parser = yacc.yacc(outputdir=os.path.dirname(__file__)) + + + + + |