5.1 Stripping leading and trailing spaces from a string
Unfortunately there's a bug in this program: readln reads in a line including the newline.
We can fix this and remove excess spaces at the same time.
write$ stdout,"Enter your name: "; fflush stdout; var name = strip (readln$ stdin); writeln$ stdout, "Hello " + name + "!";
Bugs Bunny
Enter your name: Bugs Bunny Hello Bugs Bunny!
This uses the function strip from the String module
to remove leading and trailing whitespace.
In this case, whitespace includes spaces, tabs, and newlines.
5.1.1 Slicing strings
It's common to use just a portion of a string, and here convenience is king. In Python this is called "slicing" strings. Supposing we wanted to take 13 characters from a string, starting at the third character, we could use the following:
println$ "Hello world, how are you?!".[3 to 16];
lo world, how
5.1.2 Concatenation
Felix supports concatenation (joining) of strings via the "+" (plus) operator. You can think of it as "adding" strings together, but be aware that this operation is different from adding numbers together. We differentiate these operations by the use of types. When two strings are added together, then we use string concatenation. When two integers are added together, then we use standard arithmetic. When the types are mixed, we issue a type error. Later on, we will see how these decisions are made and add some special cases of our own.
println$ "abc" + "def"; // valid concatenation of two strings
abcdef
println$ "abc" + 1; // type error (mixing string and int)
println$ "abc" + 1.str; // convert 1 to "1" before concatenating
abc1