The text buffer

The string is assembled piece by piece and sits inside the processor until it is handed out

easyYou need: Number, object and text, Properties of buildings

Every processor has a text buffer — a string that print appends values to, one after another. While it is inside, nobody sees it: not the player, not the neighbouring blocks.

steptick 0

Sensor0

=

 in

Print1

Print2

Print3

Print4

@counter0number

coppernullnull

textBuffer—string

Press “step” five times and watch the bottom row of the table: the buffer fills up with copper: 120 of 300. Four prints — four pieces, glued together in the order the lines ran.

Note

The game has no buffer row: there the buffer is invisible, and the only way to learn its contents is to hand it out. Here it is shown as a separate row in the variables table — otherwise half the printing lessons would have to be explained with hand gestures.

The language has no string concatenation

The familiar "copper: " + copper does not exist in mlog: op add with a string gives a number, not a string. Only the buffer can join text, and it does so in exactly one way — one piece per instruction.

Hence the usual shape of such a program:

print "copper: "
print copper
print " of "
print 300

Four lines for one line of text is normal. When there are many pieces, format comes to the rescue: it substitutes values into a ready template.

The buffer is not endless

It holds 400 characters. Everything that does not fit is simply not appended: there is no error and no warning — the end of the line is just cut off.

Four hundred characters is a lot for a caption and not much for a report. Printing in a loop overflows the buffer unnoticed, and the display or the block shows exactly the first part.

Silent failure

The buffer is shared across the processor and lives between iterations: if it is not handed out, the next iteration’s print keeps appending to the old contents. A hundred iterations later it is a porridge of a hundred repeats of one line — right up to the 400 character limit.

The buffer has to be handed out in the same iteration it was filled in.

Remember

• print appends a value to the processor’s text buffer and shows nothing.
• The buffer is one per processor, invisible in the game, and lives between iterations.
• The language has no string concatenation: text is assembled piece by piece, one print per piece.
• The buffer holds 400 characters; the excess silently disappears.

Task

Press “run” and watch what happens to the buffer: the line starts repeating itself — copper: 120 of 300copper: 120 of 300… — until it hits the limit. That is a buffer nobody handed out.

Then press “restart” and swap the second and third lines: the buffer holds 120copper: of 300. The order of the pieces is the order of execution, and the buffer does no “joining it up nicely”.

Who it is handed to so it does not pile up is the next group.