Entry
TSE: Parser: Simple: Syntax: Structure: Parameter: How to parse '(parameter1,..., parameterlast)'?
Sep 24th, 2003 14:48
Knud van Eeden,
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--- Knud van Eeden --- 24 September 2003 - 07:09 pm ------------------
TSE: Parser: Simple: Syntax: Structure: Parameter: How to parse '(
parameter1, ..., parameterlast )'?
To possibly parse the actual parameters of a procedure or a function:
For example given:
PROCMyProcedure( parameter1, parameter2, parameter3, parameter4 )
how could you possibly parse '( parameter1, parameter2, parameter3,
parameter4 )'?
---
Syntax diagram:
+----->---------------+
| |
-->--[(]-->-+->--[parameter]-->-+->--[,]-->-+-->-+-->-+-[)]-->--
| |
+--------------<---------------------+
---
Backus Naur Form (BNF) in words:
'parameters' = 1. not followed by 1 'open parenthesis': error
2. followed by 1 'open parenthesis'
1. not followed by 1 or more 'parameters': error
2. followed by 1 or more 'parameters'
1. not followed by a 'comma'
1. not followed by a 'closed parenthesis': error
2. followed by a 'closed parenthesis'
2. followed by a 'comma'
---
Note: so this structure is a clear binary tree,
all the time totally 2 possibilities per branch (a correct path, and a
NOT correct path)
NOT ok
+-------
|
|
|
| NOT ok
-----+ +-------
| |
| |
| |
| | NOT ok
+------------+ +-------
ok | |
| |
| |
| |
+------------+
ok |
|
|
|
+-------
ok
---
If it is OK, you take off that word, and continue.
If it is NOT OK, you show an error message, and exit (=return) from
this subroutine.
---
Pseudocode:
if not '(', error, return false
get '('
repeat
if not 'parameter', error, return false
get 'parameter'
if ',' get ',' : commaB=true
until ( not commaB ) or ')'
if not ')', error, return false
get ')'
---
So you see that this source code strictly follows the binary tree, with
3 times a possible error, as a direct reflection of the 3 possible
error branches of the binary tree.
---
Translation of pseudocode in a TSE program:
Message( FNParserSyntaxParameterB( "( parameter1 , parameter2 ,
parameter3 , parameter4 , parameter5 )" ) // gives e.g. TRUE // note:
use also spaces between the commas ',' for simplicity
--- cut here ----------------------------------------------------------
FORWARD INTEGER PROC FNParserSyntaxParameterB( STRING s1 )
FORWARD INTEGER PROC FNStringCheckEqualB( STRING s1, STRING s2 )
FORWARD INTEGER PROC FNStringCheckIsVariableB( STRING s1 )
FORWARD INTEGER PROC FNStringGetLengthI( STRING s1 )
FORWARD INTEGER PROC FNTokenCheckIsCommaB( STRING s1 )
FORWARD INTEGER PROC FNTokenCheckIsParameterB( STRING s1 )
FORWARD INTEGER PROC FNTokenCheckIsParenthesisCloseB( STRING s1 )
FORWARD INTEGER PROC FNTokenCheckIsParenthesisOpenB( STRING s1 )
FORWARD INTEGER PROC FNTokenCheckIsVariableB( STRING s1 )
FORWARD PROC Main()
FORWARD STRING PROC FNStringDeleteWordFrontS( STRING s1, STRING s2 )
FORWARD STRING PROC FNStringGetCarS( STRING s1 )
FORWARD STRING PROC FNStringGetCdrS( STRING s1 )
FORWARD STRING PROC FNStringRemoveSpaceBeginS( STRING s1 )
// --- MAIN --- //
PROC Main()
Warn( FNParserSyntaxParameterB( "( parameter1 , parameter2 ,
parameter3 , parameter4 , parameter5 )" ) ) // gives e.g. TRUE //
note: use also spaces between the commas ',' for simplicity
Warn( FNParserSyntaxParameterB( "( parameter1 parameter2 ,
parameter3 , parameter4 , parameter5 )" ) ) // gives e.g. FALSE //
note: use also spaces between the commas ',' for simplicity
END
<F12> Main()
// --- LIBRARY --- //
// library: parser: syntax: parameter (filenamemacro=syntpasp.s) [kn,
ni, we, 24-09-2003 18:55:42]
INTEGER PROC FNParserSyntaxParameterB( STRING inS )
// e.g. PROC Main()
// e.g. Warn( FNParserSyntaxParameterB( "( parameter1 , parameter2 ,
parameter3 , parameter4 , parameter5 )" ) ) // gives e.g. TRUE //
note: use also spaces between the commas ',' for simplicity
// e.g. Warn( FNParserSyntaxParameterB( "( parameter1 parameter2 ,
parameter3 , parameter4 , parameter5 )" ) ) // gives e.g. FALSE //
note: use also spaces between the commas ',' for simplicity
// e.g. END
// e.g.
// e.g. <F12> Main()
STRING s[255] = inS
INTEGER tokencommaB = FALSE
IF NOT FNTokenCheckIsParenthesisOpenB( s ) Warn( 'error: no open
parenthesis found:' + ' ^' + s ) RETURN( FALSE ) ENDIF // if not '(',
error, return false
s = FNStringGetCdrS( s ) // take off first word of the remaining
string, thus take off '(' // get '('
REPEAT // repeat
IF NOT FNTokenCheckIsParameterB( s ) Warn( 'error: no parameter
found:' + ' ^' + s ) RETURN( FALSE ) ENDIF // if not 'parameter',
error, return false
s = FNStringGetCdrS( s ) // take off first word of the remaining
string, thus take off parameter // get 'parameter'
IF FNTokenCheckIsCommaB( s ) s = FNStringGetCdrS( s ) tokencommaB =
TRUE ENDIF // if ',' get ',' : commaB=true
UNTIL ( NOT tokencommaB ) OR FNTokenCheckIsParenthesisCloseB( s ) //
until ( not commaB ) or ')'
IF NOT FNTokenCheckIsParenthesisCloseB( s ) Warn( 'error: no comma or
close parenthesis found:' + ' ^' + s ) RETURN( FALSE ) ENDIF // if
not ')', error, return false
s = FNStringGetCdrS( s ) // take off first word of the remaining
string, thus take off ')' // get ')'
RETURN( TRUE )
END
// library: token: check: is: parenthesis: open
(filenamemacro=chectopo.s) [kn, ni, we, 24-09-2003 18:49:37]
INTEGER PROC FNTokenCheckIsParenthesisOpenB( STRING s )
// e.g. PROC Main()
// e.g. Message( FNTokenCheckIsParenthesisOpenB( "( test )" ) ) //
gives TRUE
// e.g. END
// e.g.
// e.g. <F12> Main()
STRING firstwordS[255] = ""
firstwordS = FNStringGetCarS( s ) // get first word
RETURN( FNStringCheckEqualB( firstwordS, "(" ) )
END
// library: string: get: word: token: get: rest: FNCdr(): Get a
string, without the first word (words delimited by a space " " (=space
delimited list)). E.g. Message( FNStringGetCarS( "Knud is the
best" ) ) gives "Knud" // (filenamemacro=getstgcd.s) [kn, ni, zo, 02-
08-1998 15:54:17]
STRING PROC FNStringGetCdrS( STRING s )
// e.g. PROC Main()
// e.g. STRING s1[255] = FNInitializeNewStringS()
// e.g. s1 = FNStringGetInputS( "string: get: word: token: get:
rest: s = ", "this is a test" )
// e.g. IF FNEscapeB( s1 ) RETURN() ENDIF
// e.g. Message( FNStringGetCdrS( s1 ) ) // gives e.g. "this is a
test"
// e.g. END
// e.g.
// e.g. <F12> Main()
RETURN( FNStringRemoveSpaceBeginS( FNStringDeleteWordFrontS(
FNStringRemoveSpaceBeginS( s ), FNStringGetCarS( s ) ) ) ) // Remove
trailing spaces, determine the First word. Delete the first word
(=FNCarS), and finally remove the trailing spaces from the result
END
// library: token: check: is: parameter (filenamemacro=chectoip.s)
[kn, ni, we, 24-09-2003 18:50:18]
INTEGER PROC FNTokenCheckIsParameterB( STRING s )
// e.g. PROC Main()
// e.g. Message( FNTokenCheckIsParameterB( "parameter1" ) ) // gives
e.g. TRUE
// e.g. END
// e.g.
// e.g. <F12> Main()
STRING firstwordS[255] = ""
firstwordS = FNStringGetCarS( s ) // get first word
RETURN( FNTokenCheckIsVariableB( firstwordS ) ) // assume a parameter
(to keep the simplicity) is a (usual) variable name
END
// library: token: check: is: comma (filenamemacro=chectoic.s) [kn,
ni, we, 24-09-2003 18:50:22]
INTEGER PROC FNTokenCheckIsCommaB( STRING s )
// e.g. PROC Main()
// e.g. Message( FNTokenCheckIsCommaB( ", test" ) ) // gives TRUE
// e.g. END
// e.g.
// e.g. <F12> Main()
STRING firstwordS[255] = ""
firstwordS = FNStringGetCarS( s ) // get first word
RETURN( FNStringCheckEqualB( firstwordS, "," ) )
END
// library: token: check: is: parenthesis: close
(filenamemacro=chectopc.s) [kn, ni, we, 24-09-2003 18:50:15]
INTEGER PROC FNTokenCheckIsParenthesisCloseB( STRING s )
// e.g. PROC Main()
// e.g. Message( FNTokenCheckIsParenthesisCloseB( ") test" ) ) //
gives TRUE
// e.g. END
// e.g.
// e.g. <F12> Main()
STRING firstwordS[255] = ""
firstwordS = FNStringGetCarS( s ) // get first word
RETURN( FNStringCheckEqualB( firstwordS, ")" ) )
END
// library: string: get: word: token: get: first: FNStringGetCarS():
Get the first word of a string (words delimited by a space " " (=space
delimited list)). (filenamemacro=getstgca.s) [kn, ni, zo, 02-08-1998
15:54:17]
STRING PROC FNStringGetCarS( STRING s )
// e.g. PROC Main()
// e.g. STRING s1[255] = FNInitializeNewStringS()
// e.g. s1 = FNStringGetInputS( "string: get: word: token: get:
first: s = ", "this is a test" )
// e.g. IF FNEscapeB( s1 ) RETURN() ENDIF
// e.g. Message( FNStringGetCarS( s1 ) ) // gives e.g. "this"
// e.g. END
// e.g.
// e.g. <F12> Main()
//
// variation: RETURN( FNStringGetTokenFirstS( s, " " ) )
RETURN( GetToken( s, " ", 1 ) ) // faster, but not central
END
// library: string: equal: are two given strings equal? (stored
in 'checstcf.s') [kn, zoe, wo, 04-10-2000 18:23:27]
INTEGER PROC FNStringCheckEqualB( STRING s1, STRING s2 )
// e.g. PROC Main()
// e.g. STRING s1[255] = FNInitializeNewStringS()
// e.g. STRING s2[255] = FNInitializeNewStringS()
// e.g. s1 = FNStringGetInputS( "string: check: equal: first string
= ", "a" )
// e.g. IF FNEscapeB( s1 ) RETURN() ENDIF
// e.g. s2 = FNStringGetInputS( "string: check: equal: second string
= ", "a" )
// e.g. IF FNEscapeB( s2 ) RETURN() ENDIF
// e.g. Message( FNStringCheckEqualB( s1, s2 ) ) // gives e.g. TRUE
when string1 is equal to string2
// e.g. END
// e.g.
// e.g. <F12> Main()
//
// // <F12> PROCMessage( FNStringCheckEqualB( "knud", "knud" ) ) //
gives TRUE
// // <F12> PROCMessage( FNStringCheckEqualB( "knud", "van" ) ) //
gives FALSE
RETURN( s1 == s2 )
END
// library: string: space: remove: begin (filenamemacro=remostsb.s)
[kn, ri, th, 15-02-2001 06:06:51]
STRING PROC FNStringRemoveSpaceBeginS( STRING s )
// e.g. PROC Main()
// e.g. STRING s[255] = FNInitializeNewStringS()
// e.g. s = FNStringGetInputS( "string: space: remove: begin: string
= ", " test " )
// e.g. IF FNEscapeB( s ) RETURN() ENDIF
// e.g. Message( "'", FNStringRemoveSpaceBeginS( s ), "'" ) // gives
e.g. "test "
// e.g. END
// e.g.
// e.g. <F12> Main()
RETURN( LTrim( s ) )
END
// library: string: word: token: delete: first: delete 1 occurence of
a given other string in front of a given string. E.g.
StringWordDeleteFront( "00001234567", "0" ) gives "0001234567".
Possible application: deleting the '0' in front of a phonenumber (e.g.
when dialing internationally). [kn, ni, zo, 02-08-1998 16:30:45]
STRING PROC FNStringDeleteWordFrontS( STRING s, STRING deleteS )
// e.g. <F12> PROCMessage( FNStringDeleteWordFrontS( "this
is", "this" ) ) // gives " is"
// e.g. <F12> PROCMessage( FNStringDeleteWordFrontS( "the
girl", "the" ) ) // gives " girl"
// STRING PROC FNStringWordDeleteFirstS( STRING s, STRING deleteS )
INTEGER lengthdeleteI = FNStringGetLengthI( deleteS )
RETURN( SubStr( s, lengthdeleteI + 1, FNStringGetLengthI( s ) -
lengthdeleteI ) )
END
// library: token: check: is: variable (filenamemacro=chectoiw.s) [kn,
ni, we, 24-09-2003 23:29:05]
INTEGER PROC FNTokenCheckIsVariableB( STRING s )
// e.g. PROC Main()
// e.g. Warn( FNTokenCheckIsVariableB( "thisisavariable1" ) ) //
gives 'TRUE'
// e.g. Warn( FNTokenCheckIsVariableB( "thisis avariable1" ) ) //
gives 'TRUE' // because of first word 'thisis' in string separated by
spaces is a variable
// e.g. Warn( FNTokenCheckIsVariableB( "9thisis avariable1" ) ) //
gives 'FALSE' // because of first word '9this' starting with a digit
// e.g. Warn( FNTokenCheckIsVariableB( "thisis&avariable1" ) ) //
gives 'FALSE' // because of '&' character
// e.g. END
// e.g.
// e.g. <F12> Main()
STRING firstwordS[255] = FNStringGetCarS( s ) // take off first word
(in a string separated by spaces)
RETURN( FNStringCheckIsVariableB( firstwordS ) )
END
// library: string: line: length: what is the length
(filenamemacro=getstgle.s) [kn, ri, wo, 25-11-1998 20:20:58]
INTEGER PROC FNStringGetLengthI( STRING s )
// e.g. PROC Main()
// e.g. STRING s1[255] = FNInitializeNewStringS()
// e.g. s1 = FNStringGetInputS( "string: line: length: string
= ", "this is a test" )
// e.g. IF FNEscapeB( s1 ) RETURN() ENDIF
// e.g. Message( FNStringGetLengthI( s1 ) ) // gives e.g. 14
// e.g. END
// e.g.
// e.g. <F12> Main()
//
// e.g. // <F12> Message( FNStringGetLengthI( "knud" ) ) // gives 4
// e.g. // <F12> Message( FNStringGetLengthI( "the" ) ) // gives 3
RETURN( Length( s ) )
END
// library: string: check: is: variable (filenamemacro=chectoiv.s)
[kn, ni, we, 24-09-2003 18:23:35]
INTEGER PROC FNStringCheckIsVariableB( STRING s )
// e.g. PROC Main()
// e.g. Warn( FNStringCheckIsVariableB( "thisisavariable1" ) ) //
gives 'TRUE'
// e.g. Warn( FNStringCheckIsVariableB( "thisis avariable1" ) ) //
gives 'FALSE' // because of space
// e.g. Warn( FNStringCheckIsVariableB( "9thisis avariable1" ) ) //
gives 'FALSE' // because of starting with a digit
// e.g. Warn( FNStringCheckIsVariableB( "thisis&avariable1" ) ) //
gives 'FALSE' // because of '&' character
// e.g. END
// e.g.
// e.g. <F12> Main()
// RETURN( IsAlpha( s ) ) // variation
INTEGER I = 0
INTEGER totalI = FNStringGetLengthI( s )
IF NOT ( s[1] IN 'A'..'Z', 'a'..'z', '_' ) RETURN( FALSE ) ENDIF //
first character alphanumeric character or underscore
I = 2 - 1
REPEAT
I = I + 1
IF NOT ( s[I] IN 'A'..'Z', 'a'..'z', '_', '0'..'9' ) RETURN( FALSE )
ENDIF // each character (after the first) should be alphanumeric,
underscore or a digit
UNTIL I >= totalI
RETURN( TRUE )
END
--- cut here ----------------------------------------------------------
---
---
Internet: see also:
TSE: Parser: Simple: Syntax: Structure: Parameter: How to parse the
initialization of a new object?
http://www.faqts.com/knowledge_base/view.phtml/aid/24689/fid/1236
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