package org.jabref.logic.bst;
import java.util.Stack;
import org.jabref.logic.bst.VM.BstEntry;
import org.jabref.logic.bst.VM.BstFunction;
/**
The |built_in| function {\.{text.prefix\$}} pops the top two literals
(the integer literal |pop_lit1| and a string literal, in that order).
It pushes the substring of the (at most) |pop_lit1| consecutive text
characters starting from the beginning of the string. This function
is similar to {\.{substring\$}}, but this one considers an accented
character (or more precisely, a ``special character''$\!$, even if
it's missing its matching |right_brace|) to be a single text character
(rather than however many |ASCII_code| characters it actually
comprises), and this function doesn't consider braces to be text
characters; furthermore, this function appends any needed matching
|right_brace|s. If any of the types is incorrect, it complains and
pushes the null string.
*
*/
public class TextPrefixFunction implements BstFunction {
private final VM vm;
public TextPrefixFunction(VM vm) {
this.vm = vm;
}
@Override
public void execute(BstEntry context) {
Stack<Object> stack = vm.getStack();
if (stack.size() < 2) {
throw new VMException("Not enough operands on stack for operation text.prefix$");
}
Object o1 = stack.pop();
if (!(o1 instanceof Integer)) {
vm.warn("An integer is needed as first parameter to text.prefix$");
stack.push("");
return;
}
Object o2 = stack.pop();
if (!(o2 instanceof String)) {
vm.warn("A string is needed as second parameter to text.prefix$");
stack.push("");
return;
}
stack.push(BibtexTextPrefix.textPrefix((Integer) o1, (String) o2, vm));
}
}