= Functions =
[[TracNav]]

== Built-In Functions ==

=== base64_decode( arg:string ) : string ===

This function decodes the given string that must be Base64 (defined in RFC 2045) encoded. 

{{{
"/test" = "[" + base64_decode("aGVsbG8gd29ybGQ=") + "]"; 
# will be the string "[hello world]" 
}}}

=== clone( arg:element ) : element ===

This function returns a clone (copy) of the given argument. 

=== create( name:string, . . . ) : nlist ===

This function returns the named list which is the result of the execution of the structure template identified 
by the given name; the optional extra parameters must be pairs of key and value and will add or modify 
the result accordingly (a bit like with nlist). 

{{{
# description of a CD mount entry (but the device is unknown) 
structure template mount_cdrom; 
"device" = undef; 
"path" = "/mnt/cdrom"; 
"type" = "iso9660"; 
"options" = list("noauto", "owner", "ro"); 
# our first mount entry is the CD coming from hdc 
"/system/mounts/0" = create("mount_cdrom", "device", "hdc"); 
# this is exactly equivalent to the following two lines 
"/system/mounts/0" = create("mount_cdrom"); 
"/system/mounts/0/device" = "hdc"; 
}}}

=== debug( string message ) ===

This function prints the given message on stdout when debugging is enabled with the DEBUG USER 
flag. 
{{{
# print the value of x if it is positive 
if (x > 0) 
debug("x is positive: " + to_string(x)); 
}}}

=== delete( arg:variable ) ===

This function deletes the element identified by the ”variable expression” (i.e. variable name with optional 
subscript such as foo or foo[123] or foo[123][”abc”]. . . ). 
{{{
# the following will put the list ("a", "c") at path "/x" 
"/x" = { 
x = list("a", "b", "c"); 
delete(x[1]); 
return(x); 
}; 
}}}

=== error( message:string ) ===

This function prints the given message on stderr and aborts the compilation. 

{{{
# user function requiring one long argument 
define function foo = { 
if (argc != 1) 
error("foo(): wrong number of arguments: " + to_string(argc)); 
if (!is_long(argv[0])) 
error("foo(): argument is not a long"); 
# normal processing... 
}; 
}}}

=== escape( arg:string ) : string ===

This function escape non alphanumeric characters in the given string so that it can be used inside paths, 
for instance as an named list key. 

{{{
"/test" = escape("1+1"); 
# will be the string "1_2b1" 
}}}

=== exists( arg:variable ) : boolean ===

This function checks if the ”variable expression” (see delete function) corresponds to an existing 
element.

=== exists( path:string ) : boolean ===

This function checks if the path corresponds to an existing element. 

=== exists( template:string ) : boolean ===

This function checks if the given template exists. 

=== first( arg:resource, key:identifier, value:identifier ) : boolean ===

This function resets the iterator associated with arg so that it points to its first child element; if there is 
one (i.e. if the resource is not empty), sets the variable key to the ”key” of this element (i.e. a long if arg 
is a list or a string if it is a nlist) and the variable value to the child element itself and return true; if key 
or value is undef, don’t assign it; if there is no such child element, simply return false. 

{{{
# compute the sum of the elements inside numlist 
numlist = list(1, 2, 4, 8); 
sum = 0; 
ok = first(numlist, k, v); 
while (ok) { 
sum = sum + v; 
ok = next(numlist, k, v); 
}; 
# sum will be 15 
# put the list of all the keys of table inside keys 
table = nlist("a", 1, "b", 2, "c", 3); 
keys = list(); 
ok = first(table, k, v); 
while (ok) { 
keys[length(keys)] = k;ok = next(table, k, v);
}; 
# keys will be ("a", "b", "c") 
}}}

=== index ( sub:string, arg:string, [ start:long ] ) : long ===

This function searches for the given substring inside the given string and returns its position from the 
beginning of the string or -1 if not found; if the third argument is given, starts only from that position. 

{{{
"/s1" = index("foo", "abcfoodefoobar"); # 3 
"/s2" = index("f0o", "abcfoodefoobar"); # -1 
"/s3" = index("foo", "abcfoodefoobar", 4); # 8 
}}}

=== index ( sub:property, arg:list, [ start:long ] ) : long ===

This function searches for the given property inside the given list of properties and returns its position or 
-1 if not found; if the third argument is given, starts only from that position; it is an error if sub and arg’s 
children are not of the same type. 

{{{
# search in a list of strings 
"/l1" = index("foo", list("Foo", "FOO", "foo", "bar")); 
# will be 2 
# search in a list of longs 
"/l2" = index(1, list(3, 1, 4, 1, 6), 2); 
# will be 3 
}}}

=== index ( sub:property, arg:nlist, [ start:long ] ) : string ===

This function searches for the given property inside the given named list of properties and returns its 
name or the empty string if not found; if the third argument is given, skips that many matching children; 
it is an error if sub and arg’s children are not of the same type. 

{{{
# simple color table 
"/table" = nlist("red", 0xf00, "green", 0x0f0, "blue", 0x00f); 
"/name1" = index(0x0f0, value("/table")); 
# will be the string "green" 
"/name2" = index(0x0f0, value("/table"), 1); 
# will be the string ""
}}}

=== index ( sub:nlist, arg:list, [ start:long ] ) : long ===

This function searches for the given named list inside the given list of named lists and returns its position 
or -1 if not found; the comparison is done by comparing all the children of sub, these children must all 
be properties; if the third argument is given, starts only from that position; it is an error if sub and arg’s 
children are not of the same type or if their common children don’t have the same type. 

{{{
# search a record in a list of records 
"/l1" = index(nlist("key", "foo"), list(nlist("key", "bar", "val", 101), 
nlist("key", "foo", "val", 102))); 
# will be 1 (i.e. the second nlist) 
}}}

=== index ( sub:nlist, arg:nlist, [ start:long ] ) : string ===

This function searches for the given named list inside the given named list of named lists and returns its 
name or the empty string if not found; if the third argument is given, skips that many matching children; 
it is an error if sub and arg’s children are not of the same type or if their common children don’t have the 
same type. 

=== is_boolean( arg:element ) : boolean ===

This function checks if the given argument is a boolean. 

=== is_defined( arg:element ) : boolean ===

This function checks if the given argument is defined (i.e. is anything but undef or null). 

=== is_double( arg:element ) : boolean ===

This function checks if the given argument is a double. 

=== is_list( arg:element ) : boolean ===

This function checks if the given argument is a list. 

=== is_long( arg:element ) : boolean ===

This function checks if the given argument is a long. 

=== is_nlist( arg:element ) : boolean ===

This function checks if the given argument is a nlist. 

=== is_null( arg:element ) : boolean ===

This function checks if the given argument has a null value (i.e. is anything but null). 

=== is_property( arg:element ) : boolean ===

This function checks if the given argument is a property. 

=== is_resource( arg:element ) : boolean ===

This function checks if the given argument is a resource. 

=== is_string( arg:element ) : boolean ===

This function checks if the given argument is a string. 

=== key( arg:nlist, index:long ) : string ===

This function returns the name of the child identified by its index, this can be used to iterate through all 
the children of a named list. 

{{{
"/table" = nlist("red", 0xf00, "green", 0x0f0, "blue", 0x00f); 
"/keys" = { 
tbl = value("/table"); 
res = ""; 
len = length(tbl); 
idx = 0; 
while (idx < len) { 
res = res + key(tbl, idx) + " "; 
idx = idx + 1; 
}; 
if (length(res) > 0) 
splice(res, -1, 1); 
return(res); 
}; 
# /keys will be the string "red green blue" 
}}}

=== length( arg:string ) : long ===

This function returns the length of the given string. 

=== length( arg:resource ) : long ===

This function returns the number of children of the given resource. 

=== list( ... ) : list ===

This function returns a list made of its arguments. 

{{{
# the list of mount entries is empty 
"/system/mounts = list(); 
# we define two DNS servers 
"/system/dns/servers" = list("137.138.16.5", "137.138.17.5"); 
# this machine has only one CPU 
"/hardware/cpus" = list(create("cpu_intel_p3_850")); 
}}}

=== match( arg:string, regexp:string ) : boolean ===

This function checks if the given string matches the regular expression. 

{{{
# device_t is a string that can only be "disk", "cd" or "net" 
type device_t = string with match(self, ’ˆ(disk|cd|net)$’); 
}}}

=== matches( arg:string, regexp:string ) : list ===
This function matches the given string against the regular expression and returns the list of captured 
substrings, the first one being the complete matched string (i.e. $& in Perl). 

{{{
# IPv4 address in dotted number notation 
type ipv4 = string with { 
result = matches(self, ’ˆ(\d+)\.(\d+)\.(\d+)\.(\d+)$’); 
if (length(result) == 0) 
return("bad string"); 
i = 1; 
while (i <= 4) { 
x = to_long(result[i]); 
if (x > 255) 
return("chunk " + to_string(i) + " too big: " + result[i]); 
i = i + 1; 
}; 
return(true); 
}; 
}}}

=== merge( ... ) : resource ===

This function returns the resource which is the merge of its arguments which must be of the same type: 
either all lists or all named lists; if several named lists have children of the same name, an error occurs. 

{{{
"/x" = list("a", "b", "c"); 
"/y" = list("d", "e"); 
"/z" = merge (value("/x"), value("/y")); 
# /z will contain the list "a", "b", "c", "d", "e" 
}}}

=== next( arg:resource, key:identifier, value:identifier ) : boolean ===

This function increments the iterator associated with arg so that it points to the next child element and 
then behaves like first. 

=== nlist( ... ) : nlist ===

This function returns a named list made of its arguments which must be pairs of key (i.e. child’s name, a 
string) and value (i.e. child’s value, an element). 

{{{
# hda1 is our root filesystem 
"/system/mounts/0" = nlist("type", "ext2", "path", "/", "device", "hda1"); 
# hda2 is our /var filesystem 
"/system/mounts/1" = nlist( 
"type", "ext2", 
"path", "/var", 
"device", "hda2", 
); 
}}}

=== return( arg:element ) : element ===

This function interrupts the processing of the current DML block and returns from it with the given value, 
this is often used in user defined functions. 

{{{
function facto = { 
  if (argv[0] < 2) return(1); 
  return(argv[0] * facto(argv[0] - 1)); 
}; 
}}}

=== splice ( arg:string, start:long, length:long, [ new:string ] ) : string ===

This function deletes the substring identified by start and length (see substr’s documentation for de- 
tails) and, if a fourth argument is given, replaces it with new. 

{{{
"/s1" = splice("abcde", 2, 0, "12"); # ab12cde 
"/s2" = splice("abcde", -2, 1); # abce 
"/s3" = splice("abcde", 2, 2, "XXX"); # abXXXe 
}}}

=== splice ( arg:list, start:long, length:long, [ new:list] ) : list ===

This function deletes the children of the given list identified by start and length (see substr’s docu- 
mentation for details) and, if a fourth argument is given, replaces them with the contents of new. 

{{{
"/l1" = splice(list("a","b","c","d","e"), 2, 0, list(1,2)); 
# will be the list "a", "b", 1, 2, "c", "d", "e" 
"/l2" = splice(list("a","b","c","d","e"), -2, 1); 
# will be the list "a", "b", "c", "e" 
"/l3" = splice(list("a","b","c","d","e"), 2, 2, list("XXX")); 
# will be the list "a", "b", "XXX", "e" 
}}}

=== substr ( arg:string, start:long, [ length:long ] ) : string ===

This function returns the part of the given string characterised by its start position (starting from 0) and 
its length (if omitted, returns everything to the end of the string); if start is negative, starts that far from 
the end of the string; if length is negative, leaves that many characters off the end of the string.

{{{
"/s1" = substr("abcdef", 2); # cdef 
"/s2" = substr("abcdef", 1, 1); # b 
"/s3" = substr("abcdef", 1, -1); # bcde 
"/s4" = substr("abcdef", -4); # cdef 
"/s5" = substr("abcdef", -4, 1); # c 
"/s6" = substr("abcdef", -4, -1); # cde 
}}}

=== to_boolean( arg:property ) : boolean ===

This function converts the given property into a boolean; 0 and the empty strings are considered as false, 
everything else as true. 

=== to_double( arg:property ) : double ===

This function converts the given property into a double; it is an error if the given string does not represent 
a double. 

=== to_long( arg:property ) : long ===

This function converts the given property into a long; it is an error if the given string does not represent 
a long; if the argument is a double, it will be rounded to the nearest long. 

=== to_string( arg:property ) : string ===

This function converts the given property into a string. 

=== unescape( arg:string ) : string ===

This function replace escaped characters in the given string to get back the original string, this is the 
inverse of the escape function. 

=== value( path:string ) : element ===

This function returns the element identified by its path (which can be an external path), an error occurs if 
there is no such element. 

{{{
"/x" = 100; 
"/y" = 2 * value("/x"); 
# /y will be 200 
# we add one DNS server to the current list 
# (we need to use list() because merge() requires lists) 
"/system/dns/servers" = merge(value("/system/dns/servers"), 
list("137.138.16.5")); 
# the RAM of this machine is the same as the machine foo 
"/hardware/memory/size" = value("//foo/hardware/memory/size"); 
}}}