String prepend: Difference between revisions

Forth has no string prepend word, but adding it is not difficult. This demonstration code starts from the low level operations that Forth gives us and quickly builds a simple set of "WORDS" (sub-routines) that let us move strings from address to address. The memory format here is a simple count+text. Strings inare Forthjust return theiran address, or their address and length ontoon the data stack andso we can reference them as many times as we need to. Our prepend word makes use of the Return stack as a temporary storage for the address of the string we want to prepend. Standard Forth also provides a named general purpose buffer called PAD, so we make use of that too. With this PREPEND becomes part of the language.