String Operations
BR has one of the most powerful and easy-to-use set of methods for string manipulation in the industry. Consider the descriptions of these different methods below:
Concatenate
String concatenation is the operation of joining two or more character strings end-to-end. For example, the strings "snow" and "ball" may be concatenated to give "snowball".
In BR, the operator responsible for string concatenation is the ampersand &. So, the "snowball" example above may be carried out as follows:
00010 let string1$ = "snow" 00020 let string2$ = "ball" 00030 let result$ = string1$ & string2$ 00040 print result$ ! this will print snowball
You may concatenate as many strings as you like. Note that if you are storing the concatenated result into a string variable, then this variable needs to be dimensioned long enough to fit the combined length of all the concatenated strings. Consider the following example:
00010 let string1$ = "snow" 00020 let string2$ = "ball" 00030 let string3$ = " effect of concatenating many strings" 00040 let result$ = string1$ & string2$ & string3$ ! this will result in error
The above example results in an error, because the default length of the string result$ is 18 characters, as any BR string. The combined length of string1$, string2$, and string3$ is 45 characters. Note that the error does not result from concatenating string1$ & string2$ & string3$. The error occurs when we try to assign a 45 character value to an 18 character string result$. In order to correct the error, we need to dimension result$ to at least 45 characters or more. Below is the corrected example:
00005 dim result$*45 00010 let string1$ = "snow" 00020 let string2$ = "ball" 00030 let string3$ = " effect of concatenating many strings" 00040 let result$ = string1$ & string2$ & string3$ ! this will result in error
Advanced
For increased speed of program execution, and shorter syntax you may incorporate the following methods.
Appending
To append string2$ to string1$ means to join string2$ to the end of string1$.
To append to the end of a String you should (for maximum speed of code execution) use
X$(inf:0)="append this to end"
OR
X$(inf:inf)="append this to the end"
Here, inf denotes infinity.
So X$(inf:inf) means "the substring of X$ starting at infinity". This is particularly useful when you don't know how long your string is and do not want to calculate its length.
see also: prepend
Prepending
To prepend string1$ to string2$ means to join string1$ to the beginning of string2$.
To append to the beginning of a string you should use
X$(0:0)="append this to front"
or alternately
X$(1:0)="append this to front"
For example,
00010 dim result$*255 ! dimension long enough to fit the result 00020 let result$ = " and this is the end" 00030 let string_to_prepend$ = "this is the front" 00040 let result$(0:0) = string_to_prepend$ 00050 print result$
The output of the program above will be:
this is the front and this is the end
Substring
In BR, a substring of a string is a subset of the symbols in a string, where the order of the elements is preserved.
Therefore, "ball" is a substring of "snowball", but "bow" is not. Even though all the letters in "bow" are also contained in "snowball", they are not in the same order.
In order to extract a substring from its parent string, we must use a start and stop subscripts. The syntax
parent$(start:stop)
denotes "the substring of string parent$ starting at character start and ending at character end"
Below is an example of how subscripts can be used to extract substrings from strings:
00010 dim a$*255, b$*255 00020 let a$ = "from this long string, choose these words" 00030 let b$ = a$(24:41) 00040 print b$
The output of the above example will be:
choose these words
Modify
A BR String may be modified using its subscripts. For example, A$(4:6) uses the substring of A$ beginning with position 4 up to and including position 6; the numbers inside the parentheses could be replaced by any numeric expression. In the following example, line 40 sets element 3 of array Z$ to "XXC":
00010 LET Z$(3) = "ABC" 00020 LET A = 1 00030 LET B = 2 00040 LET Z$(3)(A:B) = "XX"
In the next example, line 40 replaces "BC" with "23" and assigns the value "A23D" to X$:
00030 LET X$ = "ABCD" 00040 LET X$(2:3) = "23"
Note that you the number of characters being replaced does not have to match the number of characters they are being replaced with. Consider the following example:
00010 dim a$*255
00020 let a$ = "beginning end"
00030 let a$(10:10) = " middle " ! here we are replacing one character (a space) with 6 characters (" middle ")
00040 print a$
The result of the example above is
beginning middle end
Insert
Prepend
To prepend string1$ to string2$ means to join string1$ to the beginning of string2$.
To append to the beginning of a string you should use
X$(0:0)="append this to front"
or alternately
X$(1:0)="append this to front"
For example,
00010 dim result$*255 ! dimension long enough to fit the result 00020 let result$ = " and this is the end" 00030 let string_to_prepend$ = "this is the front" 00040 let result$(0:0) = string_to_prepend$ 00050 print result$
The output of the program above will be:
this is the front and this is the end
Append
To append string2$ to string1$ means to join string2$ to the end of string1$.
To append to the end of a String you should (for maximum speed of code execution) use
X$(inf:0)="append this to end"
OR
X$(inf:inf)="append this to the end"
Here, inf denotes infinity.
So X$(inf:inf) means "the substring of X$ starting at infinity". This is particularly useful when you don't know how long your string is and do not want to calculate its length.
see also: prepend