Dc, aka desk calculator, is a programming language created in 1978.
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dc (desk calculator) is a cross-platform reverse-polish calculator which supports arbitrary-precision arithmetic. It is one of the oldest Unix utilities, predating even the invention of the C programming language. Like other utilities of that vintage, it has a powerful set of features but terse syntax. Read more on Wikipedia...
[Hello, world!] p
[Hello World
]n
#!/usr/bin/perl
my ($g,$e,$m) = map { "\U$_" } @ARGV;
die "$0 gen exp mod\n" unless $m;
print `echo $g $e $m | dc -e '
# Hex input and output
16dio
# Read m, e and g from stdin on one line
?SmSeSg
# Function z: return g * top of stack
[lg*]sz
# Function Q: remove the top of the stack and return 1
[sb1q]sQ
# Function X(e): recursively compute g^e % m
# It is the same as Sm^Lm%, but handles arbitrarily large exponents.
# Stack at entry: e
# Stack at exit: g^e % m
# Since e may be very large, this uses the property that g^e % m ==
# if( e == 0 )
# return 1
# x = (g^(e/2)) ^ 2
# if( e % 2 == 1 )
# x *= g
# return x %
[
d 0=Q # return 1 if e==0 (otherwise, stack: e)
d 2% Sa # Store e%2 in a (stack: e)
2/ # compute e/2
lXx # call X(e/2)
d* # compute X(e/2)^2
La1=z # multiply by g if e%2==1
lm % # compute (g^e) % m
] SX
le # Load e from the register
lXx # compute g^e % m
p # Print the result
'`;| Feature | Supported | Token | Example |
|---|---|---|---|
| Comments | ✓ | # A comment |
|
| Line Comments | ✓ | # | # A comment |
| Semantic Indentation | X |