5 Formal Syntax

5.1 Formal Syntax

5.1.1 Basics

The syntax of Euphoria is described using a form of BNF notation.

ALPHA ==: ('a' - 'z') | ('A' - 'Z')
DIGIT ==: ('0' - '9')
USCORE ==: '_'
EOL ==: new line character

IDENTIFIER ==: ( ALPHA | USCORE ) [(AlPHA | DIGIT | USCORE) ... ]

EXPRESSION ==: NUMEXPR | STREXPR | SEQEXPR | BOOLEXPR

NUMEXPR ==: (an expression that evaluates to an atom)

STREXPR ==: (an expression that evaluates to a string sequence)

SEQEXPR ==: (an expression that evaluates to an sequence)

BOOLEXPR ==: (an expression that evaluates to an atom in which zero represents 
              falsehood and non-zero represents truth)
              
BINARYEXPR ==: [ EXPRESSION BINOP EXPRESSION ]

BINOP ==: 'and' | 'or' | 'xor' | '+' | '-' | '*' | '/' 

UNARYEXPR ==: [ UNARYOP EXPRESSION ]

UNARYOP ==: 'not' | '-'

STATEMENT ==: 

STMTBLK ==: STATEMENT [STATEMENT ...]

LABEL       ==:  'label' STRINGLIT

LISTDELIM   ==:  ','

STRINGLIT   ==: SIMPLESTRINGLIT | RAWSTRINGLIT

SIMPLESTRINGLIT ==: SSLITSTART [ (CHAR | ESCCHAR) ... ] SSLITEND
SSLITSTART  ==: '"'
SSLITEND    ==: '"'
CHAR        ==: (any byte value)
ESCCHAR     ==: ESCLEAD ( 't' | 'n' | 'r' | '\' | '"' \ ''')
ESCLEAD     ==: '\'

RAWSTRINGLIT ==: DQRAWSTRING | BQRAWSTRING
DQRAWSTRING ==: '"""' [ MARGINSTR ] [CHAR ...] '"""'
BQRAWSTRING ==: '`' [ MARGINSTR ] [CHAR ...] '`'
MARGINSTR  ==: '_' ...

SCOPETYPE ==: 'global' | 'public' | 'export' | 'override'

DATATYPE ==: 'atom' | 'integer' | 'sequence' | 'object' | IDENTIFER

5.1.2 Statements

5.1.2.1 Directives

INCLUDESTMT
WITHSTMT
NAMESPACE

5.1.2.2 Variables, Constants, Enums

VARDECLARE
CONSTDECLARE
ENUMDECLARE
SLICING

5.1.2.3 Flow Control

IFSTMT
SWITCHSTMT
BREAKSTMT
CONTINUESTMT
RETRYSTMT
EXITSTMT
FALLTHRUSTMT
FORSTMT
WHILESTMT
LOOPSTMT
GOTOSTMT
CALL
IFDEFSTMT

5.1.2.4 Routines

PROCDECLARE
FUNCDECLARE
TYPEDECLARE
RETURN

5.1.2.5 include

INCLUDESTMT

 INCLUDESTMT  ==:  'include' FILEREF [ 'as' NAMESPACEID ] EOL
 FILEREF  ==:  A file path that may be enclosed in double-quotes. 
 NAMESPACEID ==: IDENTIFIER  

NOTE that after the file reference, the only text allowed is the keyword 'as' or the start of a comment. Nothing else is permitted on the same text line.

See Also: include statement

5.1.3 Sequence Slice

SLICING

SLICE      ==: SLICESTART INTEXPRESSION SLICEDELIM INTEXPRESSION SLICEEND
SLICESTART ==: '['
SLICEDELIM ==: '..'
SLICEEND   ==: ']'

See Also: Slicing of Sequences

5.1.4 if

IFSTMT

 IFSTMT  ==:  IFTEST [ ELSIF ...] [ELSE] ENDIF 
 IFTEST  ==:  'if' ATOMEXPR [ LABEL ] 'then' [ STMTBLOCK ] 
 ELSIF   ==:  'elsif' ATOMEXPR 'then' [ STMTBLOCK ] 
 ELSE    ==:  'else' [ STMTBLOCK ] 
 ENDIF   ==:  'end' 'if' 

See Also: if statement

5.1.5 ifdef

IFDEFSTMT

 IFDEFSTMT  ==:  IFDEFTEST [ ELSDEFIF ...] [ELSEDEF] ENDDEFIF 
 IFDEFTEST  ==:  'ifdef' DEFEXPR 'then' [ STMTBLOCK ] 
 ELSDEFIF   ==:  'elsifdef' DEFEXPR 'then' [ STMTBLOCK ] 
 ELSEDEF    ==:  'elsedef' [ STMTBLOCK ] 
 ENDDEFIF   ==:  'end' 'ifdef' 
 DEFEXPR    ==:  DEFTERM [ DEFOP DEFTERM ]
 DEFTERM    ==:  [ 'not' IDENTIFIER ]
 DEFOP      ==:  'and' | 'or'

See Also: ifdef statement

5.1.5.1 switch

SWITCHSTMT

 SWITCHSTMT  ==:  SWITCHTEST CASE [ CASE ...] [ CASEELSE ] [ ENDSWITCH ]
 SWITCHTEST  ==:  'switch' EXPRESSION [ WITHFALL ] [ LABEL ] 'do'
 WITHFALL    ==:  ('with' | 'without') 'fallthru'
 CASE        ==:  'case' CASELIST 'then' [ STMTBLOCK ]
 CASELIST    ==:  EXPRESSION [(LISTDELIM EXPRESSION) ...]
 CASEELSE    ==:  'case' 'else'
 ENDSWITCH   ==:  'end' 'switch'

See Also: switch statement

5.1.6 break

BREAKSTMT

 BREAKSTMT       ==:  'break' [ STRINGLIT ]

See Also: break statement

5.1.7 continue

CONTINUESTMT

 CONTINUESTMT       ==:  'continue' [ STRINGLIT ]

See Also: continue statement

5.1.8 retry

RETRYSTMT

 RETRYSTMT       ==:  'retry' [ STRINGLIT ]

See Also: retry statement

5.1.9 exit

EXITSTMT

 EXITSTMT       ==:  'exit' [ STRINGLIT ]

See Also: exit statement

5.1.10 fallthru

FALLTHRUSTMT

 FALLTHRUSTMT       ==:  'fallthru'

See Also: switch statement

5.1.11 for

FORSTMT

 FORSTMT ==: 'for' FORIDX [ LABEL ] 'do' [STMTBLK] 'end' 'for'
 FORIDX  ==: IDENTIFIER '=' NUMEXPR 'to' NUMEXPR ['by' NUMEXPR]

See Also: for statement

5.1.12 while

WHILESTMT

WHILESTMT ==: 
        'while' BOOLEXPR [WITHENTRY] [LABEL] 'do' STMTBLK [ENTRY] 'end' 'while'
WITHENTRY ==: 'with' 'entry'
ENTRY ==: 'entry' [STMTBLK]

See Also: while statement

5.1.13 loop

LOOPSTMT

LOOPSTMT ==: 
   'loop' [WITHENTRY] [LABEL] 'do' STMTBLK [ENTRY] 'until' BOOLEXPR 'end' 'loop'

See Also: loop until statement

5.1.14 goto

GOTOSTMT

 GOTOSMT ==: 'goto' LABEL

See Also: goto statement

5.1.15 declare a variable

VARDECLARE

VARDECLARE ==: [SCOPETYPE] DATATYPE IDENTLIST
IDENTLIST ==: IDENT [',' IDENTLIST]
IDENT ==: IDENTIFIER [ '=' EXPRESSION ]

Notes:

• The type of the EXPRESSION must be compatable with the DATATYPE.

5.1.16 declare a constant

CONSTDECLARE

CONSTDECLARE ==: [SCOPETYPE] 'constant' IDENTLIST

5.1.17 declare an enumerated value

ENUMDECLARE

ENUMDECLARE ==: [SCOPETYPE] [ ENUMVAL | ENUMTYPE ]
ENUMVAL ==: 'enum' ['by' ENUMDELTA ] IDENTLIST
ENUMDELTA ==: [ '+' | '-' | '*' | '/' ] NUMEXPR
ENUMTYPE ==: 'enum' 'type' ['by' ENUMDELTA ] IDENTLIST 'end' 'type'

5.1.18 call a procedure or function

CALL Used to call (invoke) either a procedure or a function.

CALL ==: IDENTIFIER '(' [ARGLIST] ')'
ARGLIST ==: ARGUMENT [',' ARGLIST]

See Also: procedures functions

5.1.19 declare a procedure

PROCDECLARE

PROCDECLARE ==: [SCOPETYPE] 'procedure' IDENTIFIER '(' [PARMLIST] ')' [STMTBLK] 'end' 'procedure'
PARMLIST ==: PARAMETER [',' PARMLIST]
PARAMETER ==: DATATYPE IDENTIFER

Notes:

• The procedure statement block must not contain a return statememt.

See Also: procedures

5.1.20 declare a function

FUNCDECLARE

FUNCDECLARE ==: [SCOPETYPE] 'function' IDENTIFIER '(' [PARMLIST] ')' [STMTBLK] 'end' 'function'
PARMLIST ==: PARAMETER [',' PARMLIST]
PARAMETER ==: DATATYPE IDENTIFER

Notes:

• The function statement block must contain a return statememt.

See Also: functions

5.1.21 declare a user defined type

TYPEDECLARE

TYPEDECLARE ==: [SCOPETYPE] 'type' IDENTIFIER '(' PARAMETER ')' [STMTBLK] 'end' 'type'
PARAMETER ==: DATATYPE IDENTIFER

Notes:

• The type statement block must contain a return statememt.
• It must return an integer; 0 means that the supplied argument is not of the correct type.

See Also: types

5.1.22 return the result of a function

RETURN

RETURN ==: 'return' EXPRESSION

See Also: types

5.1.23 default namespace

NAMESPACE ==: 'namespace' IDENTIFIER EOL

See Also: Using namespaces

5.1.24 with options

WITHSTMT

WITHSTMT ==: [ "with" | "without" ] WITHOPTION
WITHOPTION ==: [ "profile" | "profile_time" | "trace" | "batch" |
                 "type_check" | "indirect_includes" | "inline" | WITHWARNING ]
WITHWARNING ==: "warning" [ WARNOPT]
WARNOPT ==: SETWARN | ADDWARN | SAVEWARN | RESTOREWARN | STRICTWARN
SETWARN ==: ['='] '{' WARNLIST '}'
ADDWARN ==: ['+=' | '&='] '{' WARNLIST '}'
SAVEWARN ==: 'save'
RESTOREWARN ==: 'restore'
STRICTWARN ==: 'strict'

See Also: with / without