Here comes the first exercise in Forth programming language. If you are not acquainted, please refer to this
short intro, which also contains links to the
online interpreter and to famous book on the language.
Calculate the sum of several decimal values, given in input as a single line. Print the result. Do this in Forth.
While Forth provides . (dot) word for printing out numbers, it doesn't generally have ready word for reading
numbers from input. So you'll need to construct it.
Word key reads single character from input and leaves its ASCII code on stack. Reading char "2" for example
will push 50 onto the stack. So it would be good to read characters inside a loop, subtract 48 (code for "0")
from them, and add to previously collected result multiplied by 10.
E.g. we can define the word for reading single digit and read two-digit value:
: dig key 48 - ;
dig 10 * dig +
.
In our more general case stop reading number when space is encountered (its code is 32, anyway less than any of
digits).
Input contains a sequence of decimal numbers to be summed, in a single line. It ends with zero (and newline).
Answer should give just a single value - sum of the sequence.
Example
input:
1 4 9 16 25 0
answer:
55