Format objects into a string
String_Type Sprintf (String_Type format, ..., Integer_Type n)
Sprintf formats a string from n objects according to
format. Unlike sprintf, the Sprintf function
requires the number of items to format.
The format string is a C library sprintf style format
descriptor. Briefly, the format string may consist of ordinary
characters (not including the % character), which are copied
into the output string as-is, and a conversion specification
introduced by the % character. The % character must be
followed by at least one other character to specify the conversion:
s value is a string
f value is a floating point number
e print float in exponential form, e.g., 2.345e08
g print float as e or g, depending upon its value
c value is an ascii character
% print the percent character
d print a signed decimal integer
u print an unsigned decimal integer
o print an integer as octal
X print an integer as hexadecimal
S convert value to a string and format as string
%S is a S-lang extension which will cause the value
to be formatted as string. In fact, sprintf("%S",x) is
equivalent to sprintf("%s",string(x)).
s = Sprintf("%f is greater than %f but %s is better than %s\n",
PI, E, "Cake" "Pie", 4);
Sprintf is the number of items to format; in
this case, there are 4 items.
sprintf, string, sscanf
Concatenate strings using a delimiter
String_Type create_delimited_string (delim, s_1, s_2, ..., s_n, n)
String_Type delim, s_1, ..., s_n
Integer_Type n
create_delimited_string performs a concatenation operation on
the n strings s_1, ...,s_n, using the string
delim as a delimiter. The resulting string is equivalent to
one obtained via
s_1 + delim + s_2 + delim + ... + s_n
One use for this function is to construct path names, e.g.,
create_delimited_string ("/", "user", "local", "bin", 3);
"usr/local/bin".
The expression strcat(a,b) is equivalent to
create_delimited_string("", a, b, 2).
strjoin, is_list_element, extract_element, strchop, strcat
Extract the nth element of a string with delimiters
String_Type extract_element (String_Type list, Integer_Type nth, Integer_Type delim);
The extract_element function may be used to extract the
nth element of the delim delimited list of strings
list. The function will return the nth element of the
list, unless nth specifies more elements than the list
contains, in which case NULL will be returned.
Elements in the list are numbered from 0.
The expression
extract_element ("element 0, element 1, element 2", 1, ',')
" element 1", whereas
extract_element ("element 0, element 1, element 2", 1, ' ')
"0,".
The following function may be used to compute the number of elements in the list:
define num_elements (list, delim)
{
variable nth = 0;
while (NULL != extract_element (list, nth, delim))
nth++;
return nth;
}
Alternatively, the strchop function may be more useful. In
fact, extract_element may be expressed in terms of the
function strchop as
define extract_element (list, nth, delim)
{
list = strchop(list, delim, 0);
if (nth >= length (list))
return NULL;
else
return list[nth];
}
num_elements function used above may be recoded more
simply as:
define num_elements (list, delim)
{
return length (strchop (length, delim, 0));
}
is_list_element, is_substr, strtok, strchop, create_delimited_string
Test whether a delimited string contains a specific element
Integer_Type is_list_element (String_Type list, String_Type elem, Integer_Type delim)
The is_list_element function may be used to determine whether
or not a delimited list of strings, list, contains the element
elem. If elem is not an element of list, the function
will return zero, otherwise, it returns 1 plus the matching element
number.
The expression
is_list_element ("element 0, element 1, element 2", "0,", ' ');
2 since "0," is element number one of the list
(numbered from zero).
extract_element, is_substr, create_delimited_string
Test for a specified substring within a string.
Integer_Type is_substr (String_Type a, String_Type b)
This function may be used to determine if a contains the
string b. If it does not, the function returns 0; otherwise it
returns the position of the first occurance of b in a.
It is important to remember that the first character of a string
corresponds to a position value of 1.
substr, string_match, strreplace
Format a string suitable for parsing
String_Type make_printable_string(String_Type str)
This function formats a string in such a way that it may be used as
an argument to the eval function. The resulting string is
identical to str except that it is enclosed in double quotes and the
backslash, newline, and double quote characters are expanded.
eval, str_quote_string
Format objects into a string
String sprintf (String format, ...);
This function performs a similar task as the C function with the same
name. It differs from the S-lang function Sprintf in that it
does not require the number of items to format.
See the documentation for Sprintf for more information.
Sprintf, string, sscanf, vmessage
Parse a formatted string
Int_Type sscanf (s, fmt, r1, ... rN)
String_Type s, fmt;
Ref_Type r1, ..., rN
The sscanf function parses the string s according to the
format fmt and sets the variables whose references are given by
r1, ..., rN. The function returns the number of
references assigned, or -1 upon error.
The format string fmt consists of ordinary characters and
conversion specifiers. A conversion specifier begins with the
special character % and is described more fully below. A white
space character in the format string matches any amount of whitespace
in the input string. Parsing of the format string stops whenever a
match fails.
The % is used to denote a conversion specifier whose general
form is given by %[*][width][type]format where the brackets
indicate optional items. If * is present, then the conversion
will be performed by no assignment to a reference will be made. The
width specifier specifies the maximum field width to use for
the conversion. The type modifier is used to indicate size of
the object, e.g., a short integer, as follows.
If type is given as the character h, then if the format
conversion is for an integer (dioux), the object assigned will
be a short integer. If type is l, then the conversion
will be to a long integer for integer conversions, or to a double
precession floating point number for floating point conversions.
The format specifier is a character that specifies the conversion:
% Matches a literal percent character. No assigment is
performed.
d Matches a signed decimal integer.
D Matches a long decimal integer (equiv to `ld')
u Matches an unsigned decimal integer
U Matches an unsigned long decimal integer (equiv to `lu')
i Matches either a hexidecimal integer, decimal integer, or
octal integer.
I Equivalent to `li'.
x Matches a hexidecimal integer.
X Matches a long hexidecimal integer (same as `lx').
e,f,g Matches a decimal floating point number (Float_Type).
E,F,G Matches a double precision floating point number, same as `lf'.
s Matches a string of non-whitespace characters (String_Type).
c Matches one character. If width is given, width
characters are matched.
n Assigns the number of characters scanned so far.
[...] Matches zero or more characters from the set of characters
enclosed by the square brackets. If '^' is given as the
first character, then the complement set is matched.
Suppose that s is "Coffee: (3,4,12.4)". Then
n = sscanf (s, "%[a-zA-Z]: (%d,%d,%lf)", &item, &x, &y, &z);
n to 4, item to "Coffee", x to 3,
y to 4, and z to the double precision number
12.4. However,
n = sscanf (s, "%s: (%d,%d,%lf)", &item, &x, &y, &z);
n to 1, item to "Coffee:" and the
remaining variables will not be assigned.
sprintf, unpack, string, atof, int, integer, string_match
Delete characters from a string
String_Type str_delete_chars (String_Type str, String_Type del_set
This function may be used to delete the set of characters specified
by del_set from the string str. The result is returned.
str = str_delete_chars (str, "^A-Za-z");
A-Z and a-z from
str.
Escape characters in a string.
String_Type str_quote_string(String_Type str, String_Type qlis, Integer_Type quote)
The str_quote_string returns a string identical to str
except that all characters in the set specified by the string
qlis are escaped with the quote character, including the
quote character itself. This function is useful for making a
string that can be used in a regular expression.
Execution of the statements
node = "Is it [the coat] really worth $100?";
tag = str_quote_string (node, "\\^$[]*.+?", '\\');
tag having the value:
Is it \[the coat\] really worth \$100\?
str_uncomment_string, make_printable_string
Replace a substring of a string
Integer_Type str_replace (String_Type a, String_Type b, String_Type c)
The str_replace function replaces the first occurance of b in
a with c and returns an integer that indicates whether a
replacement was made or not. If b does not occur in a, zero is
returned. However, if b occurs in a, a non-zero integer is
returned as well as the new string resulting from the replacement.
This function has been superceded by strreplace.
strreplace
Remove comments from a string
String_Type str_uncomment_string(String_Type s, String_Type beg, String_Type end)
This function may be used to remove comments from a string s.
The parameters, beg and end, are strings of equal length
whose corresponding characters specify the begin and end comment
characters, respectively. It returns the uncommented string.
The expression
str_uncomment_string ("Hello (testing) 'example' World", "'(", "')")
"Hello World".
This routine does not handle multicharacter comment delimiters and it assumes that comments are not nested.
str_quote_string
Concatenate strings
String_Type strcat (String_Type a_1, ..., String_Type a_N)
The strcat function concatenates its N String_Type
arguments a_1, ... a_N together and returns the result.
strcat ("Hello", " ", "World");
"Hello World".
This function is equivalent to the binary operation a_1+...+a_N.
However, strcat is much faster making it the preferred method
to concatenate string.
sprintf, create_delimited_string
Chop or split a string into substrings.
String_Type[] strchop (String_Type str, Integer_Type delim, Integer_Type quote)
The strchop function may be used to split-up a string
str that consists of substrings delimited by the character
specified by delim. If the integer quote is non-zero,
it will be taken as a quote character for the delimiter. The
function returns the substrings as an array.
The following function illustrates how to sort a comma separated list of strings:
define sort_string_list (a)
{
variable i, b, c;
b = strchop (a, ',', 0);
i = array_sort (b, &strcmp);
b = b[i]; % rearrange
% Convert array back into comma separated form
return strjoin (b, ",");
}
The semantics of this strchop and strchopr have been
changed since version 1.2.x of the interpreter. Old versions of
these functions returned the values on the stack, which meant that
one could not chop up arbitrarily long strings that consist of
many substrings.
The function strchopr should be used if it is desired to have
the string chopped-up in the reverse order.
strchopr, extract_element, strjoin, strtok
Chop or split a string into substrings.
String_Type[] strchopr (String_Type str, String_Type delim, String_Type quote)
This routine performs exactly the same function as strchop except
that it returns the substrings in the reverse order. See the
documentation for strchop for more information.
strchop, extract_element, strtok, strjoin
Compare two strings
Interpret strcmp (String_Type a, String_Type b)
The strcmp function may be used to perform a case-sensitive
string comparison, in the lexicongraphic sense, on strings a and
b. It returns 0 if the strings are identical, a negative integer
if a is less than b, or a positive integer if a is greater
than b.
The strup function may be used to perform a case-insensitive
string comparison:
define case_insensitive_strcmp (a, b)
{
return strcmp (strup(a), strup(b));
}
One may also use one of the binary comparison operators, e.g.,
a > b.
strup, strncmp
Remove excess whitespace characters from a string
String_Type strcompress (String_Type s, String_Type white)
The strcompress function compresses the string s by
replacing a sequence of one or more characters from the set
white by the first character of white. In addition, it
also removes all leading and trailing characters from s that
are part of white.
The expression
strcompress (",;apple,,cherry;,banana", ",;");
"apple,cherry,banana".
strtrim, strtrans
Match a string against a regular expression
Integer_Type string_match(String_Type str, String_Type pat, Integer_Type pos)
The string_match function returns zero if str does not
match regular expression specified by pat. This function
performs the match starting at position pos (numbered from 1) in
str. This function returns the position of the start of the
match. To find the exact substring actually matched, use
string_match_nth.
string_match_nth, strcmp, strncmp
Get the result of the last call to string_match
(Integer_Type, Integer_Type) = string_match_nth(Integer_Type nth)
The string_match_nth function returns two integers describing
the result of the last call to string_match. It returns both
the offset into the string and the length of characters matches by
the nth submatch.
By convention, nth equal to zero means the entire match.
Otherwise, nth must be an integer with a value 1 through 9,
and refers to the set of characters matched by the nth regular
expression enclosed by the pairs \(, \).
Consider:
variable matched, pos, len;
matched = string_match("hello world", "\\([a-z]+\\) \\([a-z]+\\)", 1);
if (matched) (pos, len) = string_match_nth(2);
matched to 1 since a match will be found at the
first position, pos to 6 since w is offset 6 characters
from the beginning of the string, and len to 5 since
"world" is 5 characters long.
The position offset is not affected by the value of the offset
parameter to the string_match function. For example, if the
value of the last parameter to the string_match function had
been 3, pos would still have been set to 6.
Note also that string_match_nth returns the offset from
the beginning of the string and not the position of the match.
string_match
Concatenate elements of a string array
String_Type strjoin (Array_Type a, String_Type delim)
The strjoin function operates on an array of strings by joining
successive elements together separated with a delimiter delim.
If delim is the empty string "", then the result will
simply be the concatenation of the elements.
Suppose that
days = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat","Sun"];
strjoin (days,"+") will produce
"Sun+Mon+Tue+Wed+Thu+Fri+Sat+Sun". Similarly,
strjoin (["","",""], "X") will produce "XX".
create_delimited_string, strchop, strcat
Compute the length of a string
Integer_Type strlen (String_Type a)
The strlen function may be used to compute the length of a string.
After execution of
variable len = strlen ("hello");
len will have a value of 5.
bstrlen, length, substr
Convert a string to lowercase
String_Type strlow (String_Type s)
The strlow function takes a string s and returns another
string identical to s except that all upper case characters
that comprise s will be converted to lower case.
The function
define Strcmp (a, b)
{
return strcmp (strlow (a), strlow (b));
}
strup, tolower, strcmp, strtrim, define_case
Compare the first few characters of two strings
Integer_Type strncmp (String_Type a, String_Type b, Integer_Type n)
This function behaves like strcmp except that it compares only the
first n characters in the strings a and b. See
the documentation for strcmp for information about the return
value.
The expression
strcmp ("apple", "appliance", 3);
strcmp, strlen
Replace one or more substrings
(new, n) = strreplace (a, b, c, max_n)
String_Type a, b, c, rep;
Int_Type n, max_n;
The strreplace function may be used to replace one or more
occurances of b in a with c. If the integer
max_n is positive, then the first max_n occurances of
b in a will be replaced. Otherwise, if max_n is
negative, then the last abs(max_n) occurances will be replaced.
The function returns the resulting string and an integer indicating how many replacements were made.
The following function illustrates how strreplace may be used
to remove all occurances of a specified substring
define delete_substrings (a, b)
{
(a, ) = strreplace (a, b, "", strlen (a));
return a;
}
is_substr, strsub, strtrim, strtrans, str_delete_chars
Replace a character with another in a string.
String_Type strsub (String_Type s, Integer_Type pos, Integer_Type ch)
The strsub character may be used to substitute the character
ch for the character at position pos of the string
s. The resulting string is returned.
define replace_spaces_with_comma (s)
{
variable n;
while (n = is_substr (s, " "), n) s = strsub (s, n, ',');
return s;
}
strtrans function is a better choice.
The first character in the string s is specified by pos
equal to 1.
is_substr, strreplace, strlen
Extract tokens from a string
String_Type[] strtok (String_Type str [,String_Type white])
strtok breaks the string str into a series of tokens and
returns them as an array of strings. If the second parameter
white is present, then it specifies the set of characters that
are to be regarded as whitespace when extracting the tokens, and may
consist of the whitespace characters or a range of such characters.
If the first character of white is '^', then the
whitespace characters consist of all characters except those in
white. For example, if white is " \t\n,;.",
then those characters specifiy the whitespace characters. However,
if white is given by "^a-zA-Z0-9_", then any character
is a whitespace character except those in the ranges a-z,
A-Z, 0-9, and the underscore character.
If the second parameter is not present, then it defaults to
" \t\r\n\f".
The following example may be used to count the words in a text file:
define count_words (file)
{
variable fp, line, count;
fp = fopen (file, "r");
if (fp == NULL) return -1;
count = 0;
while (-1 != fgets (&line, fp))
{
line = strtok (line, "^a-zA-Z");
count += length (line);
}
() = fclose (fp);
return count;
}
strchop, strcompress, extract_element, strjoin
Replace characters in a string
String_Type strtrans (str, old_set, new_set)
String_Type str, old_set, new_set;
The strtrans function may be used to replace all the characters
from the set old_set with the corresponding characters from
new_set in the string str. If new_set is empty,
then the characters in new_set will be removed from str.
This function returns the result.
str = strtrans (str, "A-Z", "a-z"); % lower-case str
str = strtrans (str, "^0-9", " "); % Replace anything but 0-9 by space
strreplace, strtrim, strup, strlow
Remove whitespace from the ends of a string
String_Type strtrim (String_Type s [,String_Type w])
The strtrim function removes all leading and trailing whitespace
characters from the string s and returns the result. The
optional second parameter specifies the set of whitespace
characters. If the argument is not present, then the set defaults
to " \t\r\n".
strtrim_beg, strtrim_end, strcompress
Remove leading whitespace from a string
String_Type strtrim_beg (String_Type s [,String_Type w])
The strtrim_beg function removes all leading whitespace
characters from the string s and returns the result. The
optional second parameter specifies the set of whitespace
characters. If the argument is not present, then the set defaults
to " \t\r\n".
strtrim, strtrim_end, strcompress
Remove trailing whitespace from a string
String_Type strtrim_end (String_Type s [,String_Type w])
The strtrim_end function removes all trailing whitespace
characters from the string s and returns the result. The
optional second parameter specifies the set of whitespace
characters. If the argument is not present, then the set defaults
to " \t\r\n".
strtrim, strtrim_beg, strcompress
Convert a string to uppercase
String_Type strup (String_Type s)
The strup function takes a string s and returns another
string identical to s except that all lower case characters
that comprise s will be converted to upper case.
The function
define Strcmp (a, b)
{
return strcmp (strup (a), strup (b));
}
strlow, toupper, strcmp, strtrim, define_case, strtrans
Extract a substring from a string
String_Type substr (String_Type s, Integer_Type n, Integer_Type len)
The substr function returns a substring with length len
of the string s beginning at position n. If len is
-1, the entire length of the string s will be used for
len. The first character of s is given by n equal
to 1.
substr ("To be or not to be", 7, 5);
"or no"
In many cases it is more convenient to use array indexing rather
than the substr function. In fact, substr(s,i+1,strlen(s)) is
equivalent to s[[i:]].
is_substr, strlen