Changes between Initial Version and Version 1 of Doc/panc/dml/literals

Timestamp:

Mar 3, 2007, 5:56:17 PM (19 years ago)

Author:

/O=GRID-FR/C=FR/O=CNRS/OU=LAL/CN=Charles Loomis

Comment:

--

Doc/panc/dml/literals

@@ +1 @@
+= Literals =
+[[TracNav]]
+
+Constant literal values of the primitive atomic types--boolean, long, double, string, undef, and null--may appear inside of a DML block.  The following sections define the syntax for literal values of each type.
+
+== Boolean Literals ==
+
+There are exactly two possible boolean values: '''true''' and '''false'''.   They must appear as an unquoted word and completely in lowercase.
+
+== Long Literals ==
+
+Long literals may be given in decimal, hexadecimal, or octal format.  A decimal literal is a sequence of digits starting with a number other than zero.  A hexadecimal literal starts with the '0x' or '0X' and is followed by a sequence of hexadecimal digits.  An octal literal starts with a zero is followed by a sequence of octal digits.  Examples: 
+{{{
+123  # decimal long literal
+0755 # octal long literal
+0xFF # hexadecimal long literal
+}}}
+
+Long literals are represented internally as an 8-byte signed number.  Long values that cannot be represented in 8 bytes will cause a syntax error to be thrown.
+
+
+== Double Literals ==
+
+Double literals represent a floating point number.  A double literal must start with a digit and must contain either a decimal point or an exponent.  Examples:
+{{{
+0.01
+3.14159
+1e-8
+1.3E10
+}}} 
+Note that '.2' is not a valid double literal; this value must be written as '0.2'.
+
+Double literals are represented internally as an 8-byte value.  Double values that cannot be represented in 8 bytes will cause a syntax error to be thrown.
+
+== String Literals ==
+
+The string literals can be expressed in three different forms. They can be of any length and can 
+contain any character, including the NULL byte. 
+
+Single quoted strings are used to represent short and simple strings.  They cannot span several lines 
+and all the characters will appear verbatim in the string, except the doubled single quote which is used to 
+represent a single quote inside the string.  For instance:
+{{{ 
+’foo’ 
+’it’’s a sentence’ 
+’ˆ\d+\.\d+$’ 
+}}}
+This is the most efficient string representation and should be used when possible.
+
+Double quoted strings are more flexible and use the backslash to represent escape sequences.  For 
+instance: 
+{{{
+"foo" 
+"it’s a sentence" 
+"Java-style escapes: \t (tab) \r (carriage return) \n (newline)" 
+"Hexadecimal escapes: \x3d (=) \x00 (NULL byte) \x0A (newline)" 
+"Miscellaneous escapes: \" (double quote) \\ (backslash)" 
+"this string spans two lines and\
+does not contain a newline" 
+}}}
+Invalid escape sequences will cause a syntax error to be thrown.
+
+Multi-line strings can be represented using the 'here-doc' syntax, like in shell or Perl. 
+{{{
+"test" = "foo" + <<EOT + "bar"; 
+this code will assign to the path "test" the string 
+made of ‘foo’, plus this text including the final newline, 
+plus ‘bar’... 
+EOT 
+}}}
+The contents of the 'here-doc' are treated as a single-quoted string.  That is, no escape processing is done.
+
+The easiest solution to put binary data inside pan code is to base64 encode it and put it inside ”here- 
+doc” strings like in the following example: 
+{{{
+"/system/binary/stuff" = base64_decode(<<EOT); 
+H4sIAOwLyDwAA02PQQ7DMAgE731FX9BT1f8QZ52iYhthEiW/r2SitCdmxCK0E3W8no+36n2G 
+8UbOrYYWGROCgurBe4JeCexI2ahgWF5rulaLtImkDxbucS0tcc3t5GXMAqeZnIYo+TvAmsL8 
+GGLobbUUX7pT+pxkXJc/5Bx5p0ki7Cgq5KccGrCR8PzruUfP2xfJgVqHCgEAAA== 
+EOT 
+}}}
+The base64_decode() function is one of the built-in pan functions.
+
+== Other Literals ==